Category Archives for KNEE

Patellofemoral Pain and Trochlear Dysplasia

Patellofemoral knee pain and Trochlear Dysplasia are related and you can read more below.
Patellofemoral knee pain - also called anterior knee pain, is a symptom 

First of all is patellofemoral knee pain a symptom and not a disease. Trochlear Dysplasia means a shallow or flat groove for the kneecap. You might have an MRI that says trochlear dysplasia or dysplastic trochlea, which is the same. It is likely you have no symptoms from this. Nevertheless are a few patients troubled by severe chronic patellofemoral pain and trochlear dysplasia. Trochlear dysplasia increases the cartilage forces in the knee joint. What happens is that the cartilage contact area is too little. This gives high pressure on a little area. Some of these patient might be helped very well by a trochleoplasty surgery since the cartilage is unloaded. Read more on the page for anterior knee pain, the page for trochleoplasty and the page for trochlear dysplasia. It´s important to say that all types of Trochlear Dysplasia predispose to anterior knee pain and that there are several other factors that is involved in patellofemoral pain

Second opinion

Eventually get a second opinion from another patellofemoral surgeon - not just a standard orthopaedic surgeon. You are also welcome to book an online consultation with me for 175 euro prepaid. I need to see you MRI before the meeting. (contact me on [email protected]). Another solution is to accept the pain and reduce your level of activity to a lower level. The knee surgeon, Scott Dye, has for years spoken for the 'functional envelope'. This could be a solution for you. Eventually you can do some reading in the following special issue incl a paper from my hand.

Scientific evidence is slowly increasing

First I published a case report on arthroscopic trochleoplasty for chronic patellofemoral pain and trochlear dysplasia - link here. A new publication confirms that patients having chronic patellofemoral pain and trochlear dysplasia may benefit from a trochleoplasty - link here

An example

Left you see a axial view of a 36 year old women. She had severe anterior knee pain for 20 years. During her patellofemoral arthroplasty surgery there were no cartilage left in the patellofemoral joint. If she just have had a trochleoplasty when she was younger, this may have given her 20 years without pain and likely this soulc also have prevented the development of osteoarthritis

Chronic patellofemoral pain

Back in 1998 we did a follow-up on patients having anterior knee pain.We found, that about half of the patients continue to have light to moderate pain for years. About one out of 10 continues to have severe chronic pain. You can download a PDF copy here. Later have these findings been confirmed by several others. 

Is there a relationship between patellofemoral pain and patellofemoral arthritis?

The clinical entity called anterior knee pain (AKP) or patellofemoral pain (PFP) or chondromalacia patellae can leads to arthritis. This relationship has lately been revealed. It seems logic that some severely troubled patients ends up having arthritis. See the study from Conchie et al.

Plica in knee

Plica Syndrome in knee

What is a Plica Syndrome or Plica Synovialis?

There are 5 types of plicae in the knee. The two most well-known plicae are the mediopatellar (medial) plica  placed on the inner site of the kneecap and the other one is the infrapatellar plica (ligamentum mucosum) placed in the front of the knee. All the five plicae have no known functions, but they are residuals from the fetal life.

What is the problem with Plicae? 

An impact on your knee or a wrong use, can cause your plica to get inflamed and then it gets swollen. The medial plica are known to catch between the kneecap and the femoral condyle and this typically causes symptoms of inner site pain and catching. The Infrapatellar plica is attached to the Hoffa Fad and moves significantly when your knee straightens and bends. Sometimes scar tissue in the infrapatellar plica can cause anterior knee pain based upon scar tissue in the plica makes it shorten up.

What is the treatment for Plicae problems?

First of all the treatment focus rest and anti-inflammatory medicine (NSAID or steroids). When your plica has restored it self, a physiotherapist can help by restoring balance and correct movement patterns to prevent recurrence. Sometimes those treatments are not sufficient and your plicae may have to be taken care of by arthroscopic surgery. Here it is very easy to remove. Some call the Infrapatellar plica problems arthrofibrosis and call the procedure arthroscopic removal of the plica - anterior interval release. Personally I do not think this is arthrofibrosis, which is a much more serious condition giving you a stiff knee.  

The other Plicae

The three other plicae are the Suprapatellare plica that occasionally can give rise to pain above the patella in the Quadriceps tendon. The Laterale plica, that can cause outer site pain. And finally there is a plica that is localized in the rear of the knee and act as valve in front of a Baker cyst.

MRI Scan of the Knee

MRI scan of the knee - this can be a very good idea

MRI scan of the knee

In case you a having a knee problem, in most situations it will be helpful for you to have an MRI scan of the knee - to make a diagnosis or to support the diagnosis or to exclude other reasons for your problem.  MRI scans are really good for seeing meniscus tears, anterior cruciate ligament (ACL) tears and other ligament tears. The price has also declined in the past years and today it is close to 400 euro in Denmark. If your main problem is knee pain, I believe you should in most circumstances have an MRI scan of the knee and you should not have an arthroscopy without the MRI.

What is an MRI scan of the knee?

MRI scan is a magnetic resonance scan and by having a different magnetic field gradients it can generate images of the knee. Both open and closed MRI scanners exist and as far as I know, the quality from the closed ones is always better. You are supposed to lie supine, and claustrophobia is seldom a problem since your head is out site the machine.

How precise is an MRI scan of the knee?

In most situations it is very precise, however there is a number of exceptions. I will try to explain some of those here and what you need to be aware of. First of all an MRI of the knee not a answer book. A good clinical examination, in combination with your history about how the problem started and what type of pain or problem you might have, can been even more precise. Some things cannot be found by either a clinical examination or by an MRI scan and you may need to undergo an arthroscopy of your knee.

One of the problems with MRI  scans is that the result relies on who is looking at the pictures. Normally the radiologist very good, but they may overlook things and some things might be so special that they even do not  even know about it. Sometimes the radiologist has not received the appropriate information from the orthopaedic surgeon that is actually needed to look for a specific problem. The radiologist sends his report to the orthopaedic surgeon. Some orthopaedic surgeosn only look at this report and do actually look at the MRI scan pictures themselves.  If they do, they may not know precisely what to look for if it is something rare. The main reason why I write this is not to scare you, but to make you aware that if you are in a situation with continuous pain  and you have been told that the MRI is absolutely normal, you might need a second opinion.

What is typically overlooked by an MRI scan of the knee?
Anterior knee pain

I believe that one of the most common reasons to have anterior knee pain, and where also the findings seems to be normal, might be a synovial plicasince this structure can be difficult to evaluate on an MRI. Also trochlear dysplasia is often overlooked as well as patella alta. So the reason for this might be that the radiologist and/or the orthopaedic surgeon do not know how to precisely measure this. At least in Denmark some departments have cancelled the axial view, in order to save time and money. Nevertheless the axial view is the most important view in respect to kneecap instability and anterior knee pain, since this is where the trochlear dysplasia is noticed and the lateral trochlea inclination angle, the trochlear asymmetry and the TT-TG or TT-PCL is measured. So if those measurements are not mentioned and you are dealing with kneecap problems, ask the orthopaedic surgeon about those and if he does not know how to measure, perhaps you should ask for another orthopaedic opinion.

Meniscus tears

If a meniscus tear is suspected you can be 90% or more sure that the MRI will reveal this tear. However in some situations you can be unlucky that the tear is localised just between two MRI slices and therefore not visible. You might also have what is called a meniscus ramp lesion, that means that the meniscus is torn from the capsule in the rear part of the knee and is frequently associated with anterior cruciate ligament (ACL) injuries. The meniscus ramp lesions can be difficult to see both on MRI and during arthroscopy and are often overlooked. Also meniscus root tears might be overlooked on the MRI scan and "just" called a radial meniscus tear; however this type of tear can be very detrimental to the knee and in most cases surgery is indicated and that means the tear needs to be fixed or cut away. 

Meniscus ramp lesion

In the figure on the left you see the knee from the side and there is a meniscus ramp lesion; however it is rather seldom the lesion is so clearly seen. Often such a lesion can be overlooked based on a little scar that covers the lesion, and this does also apply during the arthroscopy, and therefore careful exploration might be necessary.

Meniscus root tear before and after fixation.
Meniscus root tear and seen on MRI and you also see how the meniscus extrude (glide away over the edge of the tibia)
Anterior cruciate ligament tear - ACL tear

In most situations an ACL tear is seen very precisely on MRI; however there are exceptions. In some cases the ligament is not torn, but just overstretched and has becoming too long. This can be difficult to see on an MRI, but a clinical examination will in most situations reveal this. If you already have had an ACL reconstruction and your knee has become loose again, this can be difficult to see on an MRI, since the ACL graft will in most situations not become torn, but just slowly gets longer and longer.

Cartilage lesions

MRI scan can be very clear on large cartilage lesions, however smaller lesions can be difficult to detect and in those situations is the arthroscopy much more precise.

Lars Blønd

Just a little about MRI scans of the knee and what you should be aware of

Normal axial view of a left knee
Lateral trochlear inclination angle

Here you see a lateral trochlear inclination angle at 7 degrees, which is a little below 11 degrees that is the threshold for calling it trochlear dysplasia. The normal angle is 21 degrees. It is important that the measurement of the inclination angle is done at the most proximal axial view, where both of the posterior femur condyles are seen. The lateral trochlear inclination angle varies substantially from the top of the groove (caudal) to the bottom (distal).

Patella Alta  - high riding kneecap

The patellotrochlear index is a more clinically relevant measurement of patellar height than other types of measurements. It is a measurement that says how big is the overlap between the trochlear groove and the kneecap. This is the only correct way to measure the height of the kneecap, and old measurements like the Insall-Salvati and Caton-Dechamp indexes are obsolete and imprecise. Those measurements do not say anything about the articulation between the patella and trochlea, and that is what patella alta is all about.

Patella Alta & Hoffa's fat pad Impingement

Above you see a figure that demonstrates a high-riding knee cap (patella alta). You also see an arrow that points to a white area. This is what is called Fat Pad Impingement. The white area is increased water content in the fat pad and this means inflammation. The inflammation is caused by the late engagement of the patella in the trochlear groove. This is due to a high riding Patella. The patella will first engage into the trochlea area when the knee is flexed several degrees. Since the pressure is not on the patella, it causes too much load on the fat pad. The increased load causes the inflammation in the Fat Pad. The solution is to bring down the kneecap. This is done with a distalisation of the tibial tubercle.

Meniscus Tears

Meniscal tears may occur on their own or together with other injuries.
Meniscal tears

In every knee there is an inner and an outer meniscus. They job is to resorb the forces between the femoral and tibial condyles as they act as shock absorbers and distribute the pressures. The meniscus can get injured and there are several types of tears depending on the type of injury. The typical mechanism of trauma is is a twist of the knee, but the injury can a occur spontaneous during running or by squatting.

In some cases of a meniscal tear an arthroscopy is needed. Typically you either cut out the damaged part of the menisci or in other situations it is possible to repair the tear by using different kinds of meniscal sutures or anchors,In most cases the meniscal tear can seen on an MRI scan, while and ultrasound scan is unreliable.Sometimes the injury is so obvious, that you go directly to an arthroscopy.

The symptoms for meniscal tears are commonly pain in the knee aggravated when the knee is loaded and especially by doing turns. This can feel like something is catching or like sharp pain. Please see below if some of the seven classic symptoms are some of those that you experience. 

  • pain in the joint line
  • stiffness and reduced range of motion
  • swelling
  • a feeling that the knee is untrustworthy
  • intermittent clicking, catching or popping
  • intermittent giving way
  • intermittent locking

Not all meniscal tears need surgery and especially in middle aged persons the symptoms can resolve, eventually helped by steroid injections and physiotherapist guide rehabilitation.Meniscal transplantations is an option in special selected cases, either by artificial menisci or by allograft menisci (menisci from (harvest from a cadaver).

Meniscal Root Tear

If you have a meniscal root tear you need surgery. This is based upon that the meniscus loose the ability to work as a shock absorber, when there is an avulsion of the meniscal root. Then the wear of cartilage will increase and this causes pain and early osteoarthritis. Unfortunately is this type of tear often overlooked by surgeons, since they are not aware that type of injuries exist. The problem is also that many radiologist, who are the ones who where supposed to see the injuries by MRI scans, also overlook those injuries. Read more here.

What if meniscal root tears are not operated? Read here

Meniscal tears and cruciate ligament tears

Meniscal tears and cruciate ligament tears often are associated, and sometimes there is also and injury to the site stabilising ligaments. My opinion is that in those situations, where you do surgery for a meniscal tear, you might as well do an concomitantly ACL reconstruction. Then you are only needed to have surgery once. If a meniscal tear is sutured, you must also stabilize the knee with an ACL reconstruction, otherwise will the meniscal repair retear.

“Unhappy triad” - That means tear of the ACL, the medial collateral ligament and the lateral outer meniscus.

There exist many types of knee injuries and here is anterior knee pain, jumpers knee, runners knee and pes anserinus pain, some of the most common, and those could be caused by overuse.

Meniscal root tear repair

Tibial Osteotomy

Tibial osteotomy is an operation where the load through the knee is moved away from the inner aspect and towards the outer aspect. The operation used to protect the articular cartilage in cases of osteoarthritis.

Tibial osteotomy

Tibial osteotomy is also called a bone wedge operation, since you either do have taken out or inserted a bone wedge in the shin. The tibial osteotomy can be useful if you have osteoarthritis, which means damaged cartilage on the inner or outer site of the knee. If you are bow legged you will have increased load on the inner site of the knee (varus knee) and just upper site if you are knock legged (valgus knee). By a tibial osteotomy the angle in the knee is corrected and the leg is realigned. This means that the high forces on the damaged part of the knee is moved towards the other site of the knee where the cartilage is good. By unload the damaged cartilage the pain can slowly resolve and the damaged cartilage can regenerate over time. If you are a tibial osteotomy the time for a total knee prosthesis can be exposed a number of years. Precisely how long is difficult to say, since it depends on the severity at the time of the surgery, but from 5 - 20 years is realistic. The earlier the longer. Before the surgery you have to undergo a special x-ray examination to see calculate the precise angle of correction needed. The information further down is in respect to when you are bow legged, since this is must more common.

An alternative to surgery is that you use an unloader brace. You then use the brace when you are loading your knee while walking or running. The princip is a spring built into the brace and this absorbs the load on the inner site of the knee. See video here

Se video her
The operation

By the surgery the shin is opened on the inner site, and by using a special guide system the bone is cut 3/4 though and a plastic wedge is inserted that precisely corrects the preoperatively planned correction. By this the leg will get about a ½ cm longer. The plastic wedge is secured by four plastic screws. The plastic material very much mimic the bone and can be left and normally it should not be removed. The IBalance method is now 10 year old and is very secure and precise and has many advantages in comparison of using a metal plate. Sometimes a corresponding arthroscopy of the knee will be done.

After the operation

You will arrive to the recovery room and I will inform you about the surgery and you will receive the surgical report before you leave.


During the surgery local anesthetic will be applicated around the knee and this last for some hours. Sometimes the anesthesiologist doctor will supplement by a nerve block. It is normal that you will have some pain for the first weeks and you can reduces this by placing some ice wrapped in a towel on the knee. This can be applicated for 20 minutes every hour.

After the discharge

You will be mounted with a brace where you will be able to bend your knee. This brace is going to be used for 8 weeks and is going to protect you leg to brake until the bone has healed sufficiently. After 2 weeks the brace can be opened safely when you sit in a sofa. After 4 weeks you can omitted the brace while sleeping and in the bath. The first 2 weeks you are only allowed to load your leg with 5 kg and after the 2 weeks you are allowed to load by 20-40 kg (if you are in doubt how much this is then take a bathroom scales). After 4 weeks you are allowed full weight bearing. You have to expect that the lower leg including the foot will get swollen the first weeks after the operation. It is also common to get some bruises and some stinging (can be reduced by NSAID ointment). To prevent deep venous thrombosis you have to take a preventing pill once a day for 10 days. It is common that you need to take some strong painkiller after the surgery such as morphine and morphine often cause constipation. Therefore it is a good idea to prevent constipation by taking some laxatives.  The site effect for this can be epistaxis and bruises and if this occurs you should only take the pill every second day. You are likely to get a palm large area with less sensation on the lower limb. Rarely some patients experience severe foot pain for the first 2 weeks.

Tibiaosteotomi - iBalance
Tibia osteotomi
Varus knee
Bowing legs - Varus knees

​This demonstrate a person having varus knees and in the right knee you see the line representing the axial load and this is going to the inner site of the knee

X-ray Tibiaosteotomy pre and postoperatively

Tibia osteotomy of a left knee before and 1 month after surgery. The transparent area is the plastic Ibalance wedge - the surgery is also called High Tibial Open Wedge Osteotomy

The picture demonstrates a knocked legged at leff and a bow legged at right

So why chose a tibial osteotomy instead of a knee prosthesis or a uniknee? First of all a knee prosthesis is not a new knee, but a combination of metal and plastic to restore the weared cartilage. A knee prosthesis is a major surgery and it is always better to preserve your own knee if possible. The results after tibial osteotomy seems today to be better than previously and better compared to having a knee prosthesis. One advantage is in average better range of movement. In general 20% says they are happy, 70% are good and 10% is bad and needs a knee prosthesis. 


Billedet viser at belastningen går på indersiden af knæet

Above you see a right knee with the line of load going through the inner site of knee

Below you can see the IBalance Tibial Osteotomy system, which are having many technically advantages compared to previously known methods. First of all it is more secure and precise. Since the plastic (PEEK) wedge is placed in site the bone is the no plate to protrude and bother. The plastic material can be left in place. This means no need for further surgery and in case you later need a knee prosthesis the wedge can still be left in place.


Du henvises til genoptræning som typisk starter 14 dage efter operationen.Træningen sigter mod at genoprette bevægeligheden i knæet og genopbygge muskulaturen i benet og genoprette balancen.Dit liv vil i en periode være besværliggjort og du vil i specielt de første 2 uger have svært ved at komme rundt med krykkestokke, fordi du ikke rigtig støtter.Du må først genoptage bilkørsel, når du i relation til benet kan føre bilen sikkert ogdette er typisk 4 uger efter operationen, dog lidt hurtigere for venstre ben end for højre ben.12-14 dage efter operationen skal du have fjernet trådene hos din egen læge. Du skal have taget røntgenbillede 4 uger efter operationen og efterfølgende skal du til kontrol hos mig, for at se hvordan helingen ser ud på røntgenbilledet. Der vil også være en kontrol igen 3-4 måneder efter operationen. Det er ikke ualmindeligt at der går mange måneder inden knæet falder til ro efter operationen. 


Rarely postoperatively infection can occur, but in those cases it is seriously and need instant treatment. In rarely cases will the bone not heal and new surgery is needed.

Tibial Tubercle Transfer

By Tibial Tubercle Osteotomy (TTO) the insertion site of the ligamentum patella on the tibia is moved either inwards or down causing a more aligned traction of the patella.

If your Patella is placed to high in relation to the groove (Patella alta), the Tibia Tubercle Transposition can bring your Patella downwards into the groove. If the Tibial Tubercle is outward placed, your Patella tends to track outwards and by medialization (moving inwards), your patella will track more correctly. The surgery should only be performed if you are having either an increased TT-TG or an decreased cartilage overlap between the patella and the trochlea groove (less than 6 mm) - read more here. A little variation of this surgery is called Fulkerson osteotomy and this can be used for a special group of patients having anterior knee pain caused by osteoarthritis in the Patellofemoral joint.

As it appears from the picture at left, the Tibial Tubercle is chiseled off and moved inwards. The bone block is fixated again by 2 - 4 screws.

This demonstrates how a Patella Alta (meaning a high riding kneecap) is operated, by replacing the tibial tuberosity to a lower position. Four titanium screws inserted in different angles, fixate the tuberosity.

By distalization of the tibial tubercle the patella have been brought into the trochlear groove

A newer and more safe technique, with an oblique cut most distal

Medialisaton of the tibial tubercle has been very popular, however due to several clinical and biomechanical studies, the surgery tend to be replaced by de-rotational osteotomies of the tibial and/or trochleoplasty surgery.

MPFL reconstruction

MPFL reconstruction is a reconstruction of the Medial Patellofemoral Ligament

What is an MPFL reconstruction?

By MPFL reconstruction surgery your injured inner ligament for the kneecap (MPFL) is replaced by a stronger ligament that keeps the patella (kneecap) in place. The ligament goes from the inner site of the patella and the quadriceps tendon towards the medial femoral condyle. The ligament is typically harvested from the back site of the thigh, by an incision over the inner site of the tibia.

Many surgeons say that you will just need an MPFL reconstruction and there is no reason do for example a trochleoplasty.

It can be right that MPFL reconstructions are very good in most situations. Nevertheless is the MPFL reconstruction just a new ligament and just like a shoelace, there is risk that it will not last more than a few years. This can be the case if there is trochlear dysplasia etc.

Is MPFL reconstructions always a good solution?

Unfortunately I see a number of patients who had MPFL reconstruction that re-rupture. I also see a number of patients who just have pain at the inner site of the knee, based on too strong forces on the ligament. Therefore make sure that you have an MRI scan and that your surgeon knows how to look for trochlear dysplasia and patella alta and increased TT-TG distance. Eventually read more here

New data indicate that the long term results are not as good as we had hoped. Check here 

This demonstrates how the new MPFL ligament looks like from the side.

Left is an example that demonstrates how an MPFL reconstruction can be performed - the picture shows how it looks just before inserting the screw that is going to secure the ligament until it has grown tight to the bone after a few months.

After the operation?

What are you allowed to do and what can you do after an MPFL reconstruction? Normally do I never prescript braces after an MPFL reconstruction. You are allowed full weight bearing and free range of movement. Already a few days after the surgery I recommend that you start to do physiotherapy guided exercises in order to regain strength and ability to bend your knee

Sick Leave after MPFL reconstruction?

For how are you going to stay away from school or work? This is a very good question, since there is huge individual variation. Some will be already back after a week, while for those have heavy physical work it may take 2-3 month. Another thing of importance is how you transport yourself from home to school or work 


When are you allowed to return to sport? This depends on what type of sport you participate. If  it is contact sport you have to wait until the muscles are finally back in force and balance, however you always need to wait at least 4 month..​

What safety level of activity is recommended after MPFL reconstruction?Normally I do not use any brace or limitation in range of movement and I allow full weight bearing. A few days after surgery physiotherapy-guided exercises are recommended.

Trochleoplasty – The arthroscopic version

This page is about the Trochleoplasty or Grooveplasty operation. This surgery deepen the groove in which the kneecap glides. Noteworthy the surgery can be done by arthroscopic technique. 


First of all sorry for this awful word trochleoplasty, however there is no simple word to better explain it. Maybe Grooveplasty would be a better term - if you have a better suggestion please do not hesitate to contact me. Trochleoplasty is a surgery for the Trochlear groove, a groove that helps the kneecap (the Patella) to stay in place. By this surgery a new and a deeper groove is created to normalize your anatomy. 

Why am I going to have a groove operation?

If you are troubled by unstable kneecap or chronic anterior knee pain, you might also have an abnormal groove. This means that the groove for your kneecap is more shallow than normal or it can be even flat or convex. In short, when your knee groove is too shallow, this tends to make you kneecap unstable. It basically means that it might either go half the way out (called subluxation) or it even dislocate. The condition of having a shallow groove is called trochlear dysplasia or dysplastic trochlea (abnormal groove). In these cases were you groove is flat, this operation called trochleoplasty, is the best option for you.

If you have a shallow groove

We know when your groove is shallow or flat, it is a result of too much bone in the center of the groove. This basically means that you have too little bony support for the kneecap. 

The Surgery 

The principle of the groove surgery is basically to deepen the groove. First is the cartilage released from the groove. Subsequently excessive bone is removed. This is followed by creation of an outer bony wall to support the patella. After that, when the groove has been deepened and re-shaped, the cartilage is re-located by means of a special blue or white bands. Those tapes or bands are later resolved. You can find picture examples by the images below. Certainly the groove operation is, from a mechanical point of view, the most anatomically correct operation to perform, if you have an abnormal groove.


After having invented the technique, I started out 12 years ago doing arthroscopic deepening trochleoplasty procedures. I used to do the groove procedure openly by the Bereiter method. I have stopped to do the open surgery. since it leaves a bigger scar, and in addition it is more painful and I believe that I can obtain better results by doing it arthroscopic in most situations.  

More about the groove surgery

By using the pinhole technique (arthroscopic), consequently the surgery becomes less traumatic for your knee , and therefore the rehabilitation is likely to become accelerated. To notice is the groove operation mostly done in combination with a reconstruction of the inner ligament for the kneecap (MPFL reconstruction).

Why go for arthroscopic trochleoplasty instead of open trochleoplasty?

By using the pinhole technique (arthroscopic), consequently the surgery becomes less traumatic for your knee , and I have had no case of excessive scar tissue (arthrofibrosis). Doing open trochleoplasty it´s a well known risk - read more here 

Is it really possible to do the surgery by arthroscopic technique?

This new paper demonstrate that in respect to all measured parameters that characterize the trochlear configuation there was significant improvement comparing pre-operative MRI scans with post-operative MRI scans. Moreover did the patient get stable patella and good subjective results - read more here - open source

Why also MPFL reconstruction?

Why is the groove surgery not enough? And why should you also have reconstructed the MFPL? (mediale patellofemoral ligament = inner ligament for kneecap). That is first of all because the MPFL is always torn when the kneecap dislocate. It does not heal normally and therefore it has to be reconstructed. Moreover it also so, that the trochlear groove, do not provide stability to your kneecap, before the kneecap reach the trochlea. Importantly this first happens after your knee is bend about 20 degrees. This means that the MPFL is needed to provides stability to your kneecap from full straightened knee and until your kneecap reach the new groove at 20 degrees of bending. Read more about MPFL reconstruction here

Arthroscopic trochleoplasty and no MPFL reconstruction. 

If you problem is chronic anterior knee pain as a consequence of a too shallow groove, and your kneecap is stable, likewise you do not need to have the ligament to stabilize the kneecap reconstructed - eventually read more in the page about anterior knee pain.

After surgery 

You are allowed full weight bearing and free range of movement, immediately after your surgery. There will not be applied any brace, but you will need crutches for approximately 3 weeks. You will only stay in hospital for approx 6 hours. Some have traveled 2000 km back home just after surgery.  Normally you start physiotherapy within 3 to 10 days after surgery. Some might think this rehabilitation regime sounds a little scary, however it have proved itself for more than ten years without any problems.

I am Lars Blond pioneer on the arthroscopic trochleoplasty. Eventually go to the front page or read my CV or download scientific papers

Trochleoplasty by pinholes = Arthroscopic Trochleoplasty

Patients have been coming from abroad to undergo the surgery. In addition I travel to where you live.

Until now I have operated patients from 13 different countries:


In case you would like a second opinion regarding your MRI or just your general knee situation, I do Zoom consultations. The cost is 225 euro. E-mail [email protected]


You can eventually go to Facebook. Check out either "Lars Blond + Trochleoplasty" or just "Trochleoplasty". Here you can notice more details and recent updates

Originally the company Arthrex helped me to develop the technique have now also produced at video in 4K quality - see it here

Arthrex is also the company that help other surgeons to learn the technique. Regularly I teach other surgeons in Arthrex Lab in Munich or I am send by Arthrex abroad to help surgeon to do their first cases.


Eventually read what some patients says in the testimonial page - or see this Youtube video called trochleoplasty gathering (Danish language but English text)


What does KneeGuru say about arthroscopic trochleoplasty? - Read here


When are you too old for this? No one know, however the trochlea cartilage have to be fairly okay, without too huge defects. The oldest one I have successfully operated was 57 years.  The youngest was 12 years.

New interesting paper for ordinary people

Latest paper about arthroscopic trochleoplasty from 2021

Research Outreach article - click here

Trochleoplasty surgery cost

The price for an isolated arthroscopic deepening trochleoplasty is approximately 9.000 euro

Patient from abroad

I have operated many patients from abroad (13 different countries and as far away as Hawaii) Some patients are willing to give advices in respect to travelling, accommodation, physiotherapy and rehabilitation etc. 

Combined surgeries

All the here mentioned surgeries can be combined and sometimes it can be necessary to do both Arthroscopic trochleoplasty, distalization of the tibial tubercle, rotational osteotomy of the femur and tibia and MPFL-reconstruction. 

Frequently asked questions:
  • The surgery typically last 1½- 2½ hours.
  • When can you fly back? This depends on the distance but this is from 1 to 10 days. A seat with the possibility to straighten the leg is needed.
  • Crutches are used for 2-4 weeks - with huge individual differences
  • No brace is needed after this type of surgery and full weight bearing is allowed
  • Some think - should I start with one type of minor surgery and if I do not work, then try another surgery - I my view only one surgery should be necessary if the right one is done from the start.
  • Only one knee is operated (in one out of three both knees are involved)
  • How long is the recovery?
    The knee will improve the first one or two years and will be fairly okay after 3 month.

More freguently asked questions:
  • When can I return to sport or job - this has very huge individual differences and if you have an sedentary job it is about 4 weeks and lighter sports is after approx. 3 month
  • Will my insurance pay? Normally they will pay for the surgery and travelling expences (still cheaper than similar surgery in US)
  • The price for a Skype consultation incl evaluation of MRI? 225 Euro.
    MRI scans can be posted by mail, by Dropbox or or similar (E-mail: [email protected])
  • The price for combined arthroscopic trochleoplasty and MPFL reconstruction is approx. 11000 euro incl implants (implant cost alone is 2000 euro)
  • For physiotherapy and exercises Physiotherapist Dorte Nielsen ( has a huge experience of training patients troubled by patellar instability, and has seen several patients after arthroscopic trochleoplasty. Dorte Nielsen has uploaded videos on YouTube.
About Aleris Hospital

Aleris Hospital is the largest private hospital in Denmark with 10 operating rooms and has very high safety. A rate of infection close to zero and with high cleanliness and has undergone accreditation after the highest international standards and use the latest technologies. All doctors are experienced doctors. All personnel speaks English.

Rehabilitation protocol after Arthroscopic Trochleoplasty and MPFL reconstruction - by Dorte Nielsen

Rehabilitation trochleoplasty
Example of an "Arthroscopic Deepening Trochleoplasty".

Before (left) and after (right). The blue band dissolves after 6 weeks and is therefore only temporary until the cartilage has healed.

MRI before (left) and after (right)
Trochlea before and and after the groove surgery 

- "It is difficult to balance a tennis ball on a football"

Second look

Two different examples of how it looks in-site the knee 3 months after a groove surgery. If you notice has the cartilage healed very nicely and blue bands/tapes are dissolved.

Second look - 3 years after

Illustration showing the tapes in place after arthroscopic trochleoplasty

Nice small scars after combined arthroscopic trochleoplasty and MFPL reconstruction

The scars after Arthroscopic Trochleoplasty and reconstruction of the medial patellofemoral ligament eight weeks postoperatively

Eight weeks after the surgery and the scars will become much more nice over time. I recommend you to use tape in the first month after surgery, since this will reduce traction in the scars. Hence you can avoid that the scars becomes wide.

Video arthroscopic trochleoplasty

Kenneth doing well one year after

Why should I also have a groove surgery and not just MPFL reconstruction?

That is a good question and some surgeon argue that it is not necessary. Maybe it is not 100% necessary if you just want stability, but if you also want a knee without anterior knee pain, trochleoplasty have to be done. Also, sometimes I see patients having trochlear dysplasia and who have had an MPFL reconstruction only. Then after some years the kneecap starts to becomes loose again because the MPFL reconstruction get loose by time. Therefore if you visit a surgeons, who do not do trochleoplasty surgery, and you do have this flatt groove. Most importantly try to get a second opinion in case this surgeon tells you that the surgery is rare, dangerous and complicated surgery since this is not correct. 

Case Study - Mikkel

Mikkel was the first patient who was operated upon with an Arthroscopic Trochleoplasty, and this was back in March 2008. Previously he had unsuccessful kneecap-stabilizing surgery and by doctor and physiotherapist he was told that he would never be able to sports again. Most noteworthy Mikkel had been troubled in both his knee since he was 8 years old and had never been able to run. Finally he underwent surgery on both his knees with the groove surgery at 29 years old. Meaning 21 years without running. 

Follow-up on Mikkel

Today is Mikkel doing well in his knees and he is running and playing soccer. He claims that the only annoyance is the sound from the knees, when he climbs stairs. Go to YouTube and listen to his and other stories during the trochleoplasty gathering in 2014. Many thanks to Asker Blønd - my son - who created this video. Click here trochleoplasty gathering.or check this video

Outcome after trochleoplasty

Generally the outcomes after groove surgery is very good, with less than 2 percent new dislocations. Consequently is the quality of life dramatically better. I have followed all my arthroscopic trochleoplasty patients for now more than 10 years and in average there as been improvements in all measured parameters and high satisfaction.  Both the technique and the results of this operation, have been published in peer reviewed journals. Today I have presented "The Arthroscopic Deepening Trochleoplasty" technique in the United States, Japan, Netherlands, UK, Sweden, Norway, Poland, Germany, Austria, Portugal and China. Moreover has the surgery been adopted by other surgeons and is now performed in ten differnet countries world wide.

Tibial Tubercle Transfer =TT?

What about having a TT osteotomy instead of a groove surgery? The fact is that no surgeon know what exactly what is best since the science has not yet given a final answer to that question. However is there many indications that the groove surgery gives better results. In addition we know that trochleoplasty surgery normalize the anatomy. Moreover does we know that patients, who have had TT surgery after a decade are having declining results. The first trochleoplasty patients I operated more than 13 years ago are still doing fine. So based on this and my clinical experience by doing both many tibial tubercle osteotomies an trochleoplasty surgeries, I prefer to do trochleoplasty if you are having severe trochlear dysplasia.

Here is the latest paper on arthroscopic deepening trochleoplasty here or simply go the page where you can find all my scientific papers

LinkedIn 2023

Photo library with some examples of arthrocopic trochleoplasty

Trochlear Dysplasia

Trochlear Dysplasia means that the groove (trochlea) for the kneecap (patella) is too flat or even dome-shaped. This knee condition is the single most important factor for having a loose kneecap.
Definition Trochlear Dysplasia

Trochlear dysplasia basically means that the groove for the kneecap have not become deep enough, since there is too much bone volume in the top of the groove or more seldom is the out part of the trochlea too low. The definition for trochlear dysplasia is an abnormal shallow, flat or even dome shaped groove. If you have trochlear dysplasia this can lead to both patella dislocation, anterior knee pain and cartilage breakdown. Your tendency to cartilage breakdown is based on too much load in this special part of the knee. Cartilage breakdown predispose to osteoarthritis. 

Why did you get trochlear dysplasia?

Basically we do not have the answer for this yet. We do not know for sure if it is innate. However there is likely some heredity involved. But breech position during foetal life may also play a role. In some patients only one knee is involved. Once I was told by a patient having trochlear dysplasia and loose kneecaps, that in her family, loose kneecaps could be traced seven generations back. Sheila Strover can explain so it is more easy to understand - Click here.

Why is it of importance with this shallow groove?

Since humans are walking upright we have developed from other animals, and the result is that the thigh muscle constantly is pulling the kneecap outwards. To compensate for this high force, humans have developed this groove to provide the kneecap stability and containment. If the groove is missing the kneecap tends to go to the outer site - called a kneecap dislocation.

Lateral Trochlea Inclination angle - LTI

The lateral trochlea inclination angle is regarded as the most important measurement for evaluation of Trochlear dysplasia. This angle says something about the osseous support for the kneecap. This is the angle of the outer part of the groove (Trochlea), compared to line in the back of the knee between the two femur condyles. In other words the more steep the outer edge of groove, the more stability it provides for the kneecap. A high angle prevents the kneecap for coming out of the joint. Further if the angle is below 9 degrees it means trochlear dysplasia (shallow groove). Please notice the examples below - left is normal - right demonstrates trochlear dysplasia. Read more here.

LTI angle measurement

This picture demonstrate how to measure in practical daily life. You place a 'postit' on the screen at the axial slice, where the femoral condyles are most prominent. The you scroll until you reach the most proximal slice where you notice cartilage, and measure the angle of the lateral trochlear and the postit. At the presented example, you are not able to measure the trochlear angle since the lateral trochlea has a convex configuration. When it is like that, it´s the same as severe trochlear dysplasia.

'Difficult to balance a tennis ball on a football' 

Trochlear depth and trochlear asymmetry

If the trochlear depth is less than 3 mm or if the trochear asymmetry is less than 40% the trochlea is dysplastic. A trochlear bump may also involved in some cases.

Dejour Classification

Dejour is a very experienced and skilled orthopedic surgeon. He has made a classification based upon x-rays, having four subgroups. It contains Dejour type A,B,C and  D. Today we mainly uses MRI or CT scans instead of x-rays. And also since the classification is not reliable, it is slowly out-faded. Instead the lateral trochlea inclination angle have been more accepted. Also some other measurements can be used.

Oswestry-Bristol Classification for trochlear dysplasia

This is a newer and more simple classification, however it a subjective classification like the Dejour Classification. When ether or not the subgroups reflects what´s of importance for stability or not, is not solved by this. 

Trochlea Bump

According to biomechanical studies, this have importance in respect to pressure in the patellofemoral joint. The pressure can be elevated and this might lead to cartilage breakdown and/or patellofemoral pain.

Patella Tilt

When your kneecap tilts, it is sometime because the outer kneecap ligament is to tight, but actually quite rare. Importantly your tilt is most often caused by trochlear dysplasia. When you have too much bone in the trochlea, consequently this causes your kneecap only to articulate on the outer part, as you might see below. Moreover this typically gives anterior knee pain or hyperpressure syndrome, based on to much pressure in the patellofemoral joint. In these cases trochleoplasty could be the right solution for you, since it reduces the pressure by unloading your joint. I some more rare cases is the patella tilt caused by increased femoral torsion - also called increased femoral anteversion.

Normal knee

Patella tilt - Trochlear dysplasia

Another Patella tilt - Trochlear dysplasia

TT-TG distance

This means Tuberositas Tibia - Trochlear Groove distance. The measure is done by CT or MRI scans. It explain how much offset the groove has in relation to where the patella tendon attaches to the tibia (Tuberositas Tibia). TT-TG distance is normally about 9 mm and if it´s more than 14 mm on MRI scans or 15-20 mm on CT scans, it´s too high. Increased TT-TG distance can also be caused by a rotational abnormality of the tibia (increased tibial external torsion). 

No Trochlear dysplasi

This is a MRI picture that demonstrates a slice of a normal knee, demonstrating the kneecap and the trochlear groove

Severe increased TT-TG distance on a CT scan in a knee having a degree of trochlear dysplasia

A drawing of how you measure the TT-TG distance. Two axial slices from the MRI or CT scan are overlapping or superimposed and thereby you can measure the distance.

Just a drawing of the same picture at left, demonstrating a TT-TG distance above 40 mm which is extreme. Dejour type D.

Article about trochlear dysplasia - click

I guess you are a bit nerdy, since you have landed on this page - in case you are even more nerdy, you can read some of the scientific papers where I have been involved - click here

Bieder Anterior Posterior measurement

When you have trochlear dysplasia and you are troubled by patellar instability read more here if you are troubled by anterior knee pain read more here

If you want to read a scientific paper about the evaluation of trochlear dysplasia you can read this paper PDF Version

Patellar Instability Overview

Patellar instability overview

A lax kneecap is a common disorder, and in the following text and subpages you can learn about this problem. Naturally it is not necessary for you to know everything there is to know in order to get treatment. However if you are a person that want to take responsibility and ask the surgeon, key questions read more.
Symptoms of unstable kneecap

For some patients with kneecap laxity the kneecap will goes out once and they will experience no further problems. Others, however, may go on to experience repeated dislocations. If the kneecap has gone out more than once, it will have a tendency to out again and again. Then things may become quite disabling. The problem can occur while doing activities, like changing direction such as in sport or dancing. For others the kneecap just seems to go out without much provocation. This can happen while walking on uneven or slippery surfaces. In some of the worst cases you need to concentrate on avoiding the kneecap popping out the groove while kneeling. In some it can be a problem while jumping in and out of a car or even during sexual activity. 

Quality of life

Your quality of life can be significantly affected, since a lot of simple daily activities must be avoided. Sometimes your disorder also might cause pain during daily life. It is very important if you are going for surgery to rule out what cause your instabiliy. Your surgery should correct the identified abnormality (or abnormalities, since there may be several factors involved).

Why me?

It is very important to find out why your kneecap dislocated. This is since you can undergo so many treatments and in order for you to have the right one, this have to be examined. This is rather complicated. I have made a site only for explaining this in order for you to ask you surgeon the critical questions - click here

The many myths

Many myths exist about loose kneecap, and one is that you will grow out of it. Mostly this disorder is worse during the teenage years. Then you learn to be more cautious and reduce your level of activity. There is furthermore a tendency for the joint to get less flexible as you age and this helps the kneecap to stay in the groove. So many grownups do not actually grow out of the condition, but they just learn to avoid the activities that provoke the dislocation.

It is just going to be trained away

Another myth is that the disorder just needs to be trained away. This is only partially true. Some may perhaps be able to avoid surgery by learning to use their knee in a more correct way. This can be via physiotherapy and by strengthening the quadriceps and gluteal muscles. A special brace that supports the kneecap can stabilize the patella. There is yet no scientific documentation that say that physiotherapy can prevent further dislocations

Easy to treat - you just need a MPFL reconstruction

The next myth is that surgery can easily treat the disorder. A significant number of patients undergo surgery only to experience that the surgery did not work as intended. As previously mentioned, is of importance to explore the reason why the kneecap dislocates. I suggest that you as a minimum have an MRI can. Then your surgery can be individualized and thereby work efficiently.

It is hereditarily

The next myth is this disorder is inherited. Actually this is true in several cases, and sometimes a dislodged kneecap can be traced back several generations. Especially if you have trochlear dysplasia.

Sorry you surgery did not work

A further myth is that if you had once undergone surgery, and it did not work, that you just need to live with it. Unfortunately this is a disorder where many patient have undergone surgery using an insufficient method. This explains why it did not help or maybe even worsened the situation. Knowledge about this disorder has changed radically over recent years. If the right surgery is done, there is a very good chance for your knee to become significantly better.

What happens when the kneecap dislocate

When the kneecap jumps out it is naturally a very unpleasant experience. Often the kneecap has to be manipulated back at the emergency department. The first time the kneecap dislocates, a ligament on the inner side is torn. This is called the Medial Patellofemoral ligament or just MPFL. Such an injury causes a lot of pain and swelling. Sometimes a fragment of the knee cartilage is loosened. In some cases a loosened piece of cartilage requires surgery to fix the piece back in place or to remove it.

How much will I get troubled?

For those troubled by a continuously loose kneecap there will be a huge variability how much distress this actually causing. However questionnaires have been developed to help both patient and surgeon to elucidate the extent of the problem. Please see an example of a questionnaire here. As previously mentioned is it not always that the kneecap jumps out again. Nevertheless it can still be very troublesome since you may experience that it nearly jumps out. This is called subluxation.

The treatment of loose kneecap

The very first time the kneecap goes out, the treatment is likely to just consist of rest, ice, compression and elevation (RICE). You should be allowed full weightbearing and full range of movement. In past years a brace for support and immobilisation was generally used. Recent research has shown that it does not have any real impact. If the knee does not get the stability wanted and the kneecap continuously is feeling loose, a kneecap stabilizing brace or surgery should be considered. Physiotherapy has also been an important part of the treatment in improving muscle balance. Still we need studies that demonstrate that it has a positive effect. Please read more about surgery here; MPFL reconstruction - Tibia tubercle osteotomy - Trochleoplasty - Rotational osteotomy

The many names for unstable kneecap

The condition of a loose kneecap has many names and here you can learn more about: dislocating kneecap, kneecap out of its groove, kneecap out of its socket, kneecap malalignment, slipped kneecap, jiggly kneecap, unstable kneecap, recurrent patellar instability, episodic patellar instability, luxating patella, unstable patella...

The condition of a loose kneecap has many names and here you can learn more about: Dislocating kneecap, kneecap out of groove, kneecap out of socket, kneecap malalignment, slipped kneecap, jiggly kneecap, unstable kneecap, recurrent patellar instability, episodic patellar instability, luxating patella, unstable patella


In case you would like a second opinion regarding your MRI or just your general knee situation, I do Zoom consultations. The cost is 225 euro.

E-mail [email protected]

Combined surgeries

All the here mentioned surgeries can be combined and sometimes it can be necessary to do both Arthroscopic trochleoplasty, distalization of the tibial tubercle, rotational osteotomy of the femur and tibia and MPFL-reconstruction.