Category Archives for KNEE

Knee Injury Overview

Below you can read about the most common knee injuries other than meniscal tears, which are covered in a separate section.

Side ligaments
The inner side and outer side ligaments are also referred to as the medial and lateral collateral ligaments (MCL and LCL). Those two ligaments gives sideways stability - and those can be partially or totally torn by a knee twist. The treatment of the two ligament injuries is different.

The mediale collateral ligament normal heals sufficiently by itself in opposition to the lateral collateral ligament. The MCL tear is treated by a site to site stabilising brace, having normal range of movement and full weight support. Normally the MCL ligament is sufficiently healed to remove the brace after 6 weeks. The LCL is typically injured together with the ACL and the recommendation is always repair/reconstruct since the tears seldom heal by themselves.

Another ligament that has been given much attention lately is the Antero Laterale Ligament (ALL) and that is an important ligament that protects the knee towards too much rotation in relation to the femur. It can sometimes be needed to reconstruct that ligament simultaneous to the ACL reconstruction.

Cartilage lesions
Cartilage lesions in the knee are common.The cartilage is a very important surface covering the bone. The cartilage is surprisingly most of all made of water and is extremely slippery in order to make the joint go smoothly and the cartilage is an important shock absorber. It is difficult to compare the cartilage with anything we know from daily life, but think about it as the peel from an orange. The cartilage can be torn off by a sudden twist or hit. The cartilage flake can float around in the knee as a loose body and cause sudden locking when it catches. The area where the cartilage is missing is a cavity, and potentially this can cause pain and mostly the knee will becomes swollen. Many cartilage lesions will slowly recover without any treatment, however some lesions continue to cause knee pain. Osteoarthritis in the knee is also a kind of cartilage lesion, however in this situation this is more a kind of cartilage thinning, based on decreased cartilage quality over time causing the cartilage to fragment and wear.

So at one end of the spectrum we do have cartilage lesions in the very young with fresh cartilage, and in the other end of the spectrum there is older people, where the cartilage starts to breakdown for more or less unknown reasons. In the middle between those types are all kind of variations. The treatment of the different types are different and this naturally makes this area of treatment very complicated. A lot of science is ongoing but still the big breakthrough is lacking. I am personally working with a study on Lipogems for treatment of osteoarthritis. This is micro-fragmented adipose tissue containing stemcells.

Treatment of cartilage lesions
Cartilage lesion in younger people (here is meant below 40 years) is typically treated by microfracture or microdrilling (Steadmann).

This is a treatment based on arthroscopic cleaning of the lesion and then small holes in the bone is applied to the button of the lesion directly into the bone. This causes some of the bone marrow and blood to float into the defect and fill it. Over time this will mature into some cartilage looking scar tissue. When such a treatment is done, the knee must not be loaded for 8 weeks, since the area has to mature in order to stand the forces. It normally takes one year before the repair tissue is 100 % healed. Unfortunately does about ⅓ not heal and in those cases a lot of advanced methods exist.

The most famous is cartilage transplantation (autologous chondrocyte transplantation - ACI). This method was started already in 1987 by Mats Brittberg and is therefore a well known technique that has been refined many times. Most people ask why not start with this instead of microfracture? The short answer is that it is troublesome and very costly and the results are only minimally better. By cartilage transplantation we harvest some cartilage and this is then regrown for some months, and then the cartilage cells are transplanted into the defect by another operation. Today is the method know as 'minced cartilage' or 'autocart'. In this method cartilage is harvested from another non-loaded area in the knee and the cartilage is cut into very small pieces and by special glute those are fixated into the cartilage defect. 

There has been attention drawn to the issue that some cartilage lesions never heal because of underlying malalignment and axis deviations. Those knees must have they imbalances simultaneous corrected by osteotomies - see for example tibia osteotomy or trochleoplasty or tibial tubercle osteotomy.

Plica synovialis enlarged

All knees do have a plica placed on the inner site of the kneecap (parapatellar) and one in the front of the knee (infrapatellar). The inner plica has no know function, but is a residual from the fetal life. Sometimes a knee impact or wrong use of the knee can cause this plica to get inflammed and the it gets swollen and catch between the kneecap and the femoral condyle. The treatment focus rest and antiinflammatory medicine (NSAID or steroids. When the plica has restored it self, a physiotherapis can help by restoring balance and correct movement patterns to prevent recurrence. Sometimes those treatments are not sufficient and the medial plica has to be taken care of by arthroscopic surgery, where it easily can be removed.

The infrapatellar plica is attached to the Hoffa Fad and moves significantly when the knee straightens and bends. Sometimes scar tissue in the plica can cause anterior knee pain based upon scar tissue in the plica - read more here

Plica synovialis
Osteoarthritis in the knee

Osteoarthritis in the knee means wear and damage of the cartilage. For more or less known and unknown factor the cartilage becomes thinner and in a bad quality situation. Some people seems not to be very affected until it gets really severe, while others are very troubled already when the wear situation starts. In my opinion this can be explained how the synovial tissue, that contains all the nerve endings, responds when the microscopic cartilage particles are going to be reabsorbed from the knee. For a small proportion of people, the synovial tissue will get swollen and painful already when it gets in contact with a small amount of cartilage particles and for those the symptoms of osteoarthritis will start concomitantly to the wear starts. This can be very frustrating since you cannot see the osteoarthritis in X-rays and MRI in the early phase of osteoarthritis. For most people the symptoms of osteoarthritis will first appear when the wear is more pronounced. The typically symptoms will then be pain after activity and night pain  Many known and unknown risk factors for osteoarthritis exist. First of all is previous injuries such as meniscal tears, cruciate ligament tears, cartilage lesions, bowed legs and fractures of importance. Also more intrinsic factors like heritage and nutrition (D-vitamin) are of importance. 

Prevention of osteoarthritis in the knee

How can you prevent further degenerative changes in the knee? First of all are you going to live a healthy live and keep your weight down. You shall avoid activities that implies a lot of stresses in the same part of knee. This could for example be walking long distances or running, when the forces are applied to the same small spot in the knee for every step. Contrary to this is activities like bicycling, rowing and swimming that are much more healthy for the knee. Actually is activity of importance for bringing fresh joint fluid to the cartilage and for this is bicycling very healthy. In cases with malalignment, meaning that something in loaded in the wrong way, it can be preventive to have surgical correction of the deformity. This is the situation when you are bowlegged or when you kneecap is tracking crooked or irregular. See Tibial osteotomy or anterior knee pain 

Loose body

This is a little piece of cartilage that is floating in the knee. It can sometimes be caught between the condyles. It can easily be removed by an arthroscopy. It can not alway be seen on MRI´s or X-rays

Baker cyst

Baker cyst´s or Popliteal cyst´s are liquid in the rear site of the knee Are you troubled by a Baker cyst there is about 90 % risk, that it is caused by a knee injury, such as a meniscal tear, cartilage lesion or an ACL rupture. If you are one of those without such an injury, don't let anyone remove your Baker cyst by open technique from the rear site of the knee, since there is a 60 % risk of relapse. The background for developing the cyst is a plica in the rear site of the knee, that both produce liquid and act as a valve, meaning that the liquid runs to the rear site into the cyst, but it cannot escape. If the cyst does not disappear by empty it and installing steroid, you need to have the cyst removed. For this you need to have a special arthroscopic procedure with removal of the plica in the rear site of the knee. Eventually read more here

Kneeguru have made a little paper on this - just click here


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.

Dislocating Patella

Unstable kneecap is a common disorder and here you can read more about why your kneecap has become unstable.

For some patients it happens once in a lifetime and after that they have no problems.

For others the kneecap continuously dislocates or subluxate. If the kneecap has been dislocated more than once, it tends to become dislocated again and again, and then of course it becomes quite troublesome. Here you can read more about why you kneecap becomes unstable
Loose kneecap

Dislocating patella is when the kneecap pops all the way out. Sometimes it just goes half the way and you the call it a subluxating kneecap. I recommend you to either before or after having read this - go to the section Patellar Instability overview.

Why does the kneecap dislocate?

There are many reasons why the kneecap becomes unstable and the four most important will be explained beneath. Some very complicated words are involved like Trochlear Dysplasia, Patella Alta, Increased TT-TG distance and increased Femoral Antetorsion, but as said this will be explained. Occasionally the kneecap is struck by a foot or something else on the inner side so hard that it pushes the kneecap out, but mostly it is a sudden twist or turn that makes the kneecap go out.

Here you can download a PDF file from a Webinar

Here you can see and listen to the Webinar - Link

Flat groove - Trochlear Dysplasia

 The most common reason for the kneecap to dislocate is that the groove (trochlea) which patella runs in when the knee is bent is either shallow, not deep enough, or dome shaped (this is called trochlear dysplasia and there is a section only for this). If the kneecap is not contained (kept in place in the groove), the patella will have a tendency to jump out, to the outside of the knee. Among those who have experienced the first kneecap dislocation and who have a shallow groove (trochlear dysplasia) two-thirds will experience another dislocation. If you have a normal groove, in contrast, the risk will only be one-third.

Why the trochlear groove is flat is that it for unknown reasons at birth it is filled with too much bone underneath the cartilage.

3D reconstructions of a normal knee to the left and a knee with a shallow groove on the right.
MRI demonstrating two different knees. On the left it is normal and on the right the groove for the kneecap is missing (Dysplastic)
Patella Alta

Patella Alta means that the patella is too high and this is an important factor for loose kneecap. If the patella is too high there is a huge risk that, at the point where it should locate itself in the groove, it will instead go to the outer side of the groove, and dislocate. Below you can see an MRI scan with a high riding kneecap.

MRI and Patella Alta

High kneecap

Distalisation of the Tibial Turbercle for normalizing anatomy

Distalisation Tibial Turbercle
Increased TT-TG distance

Increased TT-TG distance means that the Tibial Tubercle is unusually far to the outer side of the shinbone and that causes the kneecap to track outwards. This will give a tendency to pull the kneecap out of the groove and thereby dislocate or subluxate. Often the increased TT-TG distance is caused by Trochlear Dysplasia since this makes the groove go towards the inner side (yes it is right inner side and that makes the TT-TG distance increase). In those cases where the Tibial Tubercle is rotated outwards, the treatment will consist of a Tibial Tubercle Osteotomy

Increased TT-TG distance
Trochlear dysplasia

This demonstrates and axial view on CT scan or MRI scan were both the Trochlear Groove (TG) and the Tibial Tubercle (TT) are visualised. The distance between those is normally close to 9 mm - if it is above 20 mm it is far to high.

Increased Femoral Antetorsion

In some cases the patella dislocates secondary to a malrotated hip which makes the knee go inwards (increased anteversion of the femur). By clinical examination this can be suspected and in these cases a CT or MRI scan can confirm the diagnosis. The malrotation can be corrected by a femoral rotational osteotomy. Beneath you see a figure demonstrating a left femur with severe increased internal rotation, causing the patella to dislocate. The patient had previously had a failed MPFL reconstruction. She responded very well to a combined femoral rotational osteotomy and a revision MPFL, and her pain resolved completely when the internal fixation device was removed a year after.

Typically the kneecap dislocate doing activities with changing direction, such as sports or dance. In others, it feels as if the kneecap is coming out just by walking on uneven surfaces. At worst you should concentrate if not kneecap is out of joint when doing squat or getting into and out of a car. Quality of life can be significantly affected because it discourages one from many activities.


First myth

It is a myth that it is easy to deal with by doing an operation. Quite a few patients have been operated unsuccessfully, and some even several times. It is therefore important to find the true cause of the kneecap is out of joint. Always do an MRI scan and sometimes X-rays as well. Then the operation can be individualized in order to reestablish normal anatomy. Then the operation will be effective.

Second myth

Another myth is that it is hereditary and this is in fact often not a myth, but it can be true. Sometimes dislocating kneecap can be traced several generations back.

Third myth

The next myth is that you just have to live with the problem, if it is the case that you already had surgery and the surgery has not worked as intended. Knowledge about the cause of the disorder and the treatment of it has changed radically over the last few years.

Anterior Knee Pain – can it be treated surgically?

The condition of having anterior knee pain is a very common disorder. The majority of patients can successfully be treated without surgery. But why do I have this strange pain? Can something be done? Are you curious, then read more.
Anterior knee pain - a disease?

First of all is frontal knee pain a symptom and not a disease. Today we have identified many reasons to have anterior knee pain. Initial treatments of your Anterior Knee Pain ( also called Patellofemoral Pain consists two things. First of all you should try to reduce your level of activity. Next you have to try a mixture of physiotherapy-guided quadriceps and hip exercises. You should also train core stability, and eventually foot orthoses. Braces and tape, might be helpful. If you have tried all that, and that you still have chronic anterior knee pain you should read further.  

Living with pain

I guess You have been told several times to live with your pain since there is nothing wrong. Eventually you have been introduced to the model "Functional Envelope" developed by Scott Dye, or you have just by experience automatically adopted your level of activity. That solution might be fine, but in your specific case you might think, that if something could be done that would be great. It´s likely that you often have been deprecated surgery.

Surgery for anterior knee pain?

Surgery for anterior knee pain is very complicated and you should look for a surgeon with a special interest in the patellofemoral joint. It has to be a surgeon who you can trust. The surgeon also have to examine you competently. Also the surgeon needs to explain to you exactly the MRI. I normally say that "there is nothing you cannot operate on without risk of making it worse". So be alert and skeptical to what your surgeon might suggest you.

Second opinion

Eventually get a second opinion from another patellofemoral surgeon - not just a standard orthopaedic surgeon - if it´s difficult to find someone locally try and ask for help in the community.

Possible surgical solutions
  1. Arthroscopic debridement
  2. Arthroscopic plica resection (read here) 
  3. Lateral retinaculum lengthening (or lateral release) - se below
  4. Tibial tubercle medialisation (Fulkerson osteotomy)
  5. Distalisation of the tibial tubercle
  6. Arthroscopic trochleoplasty
  7. Lateral patella facetectomy
  8. Femoral derotation osteotomy - se below
  9. Tibial derotation osteotomy
  10. Tibial varus osteotomy
  11. Patellofemoral cartilage restoration
  12. Resection arthroplasty
  13. Patellofemoral arthroplasty
  14. Lateral release reversal

Chronic anterior knee 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.

What causes the pain

For a group of patients having severe chronic pain, a number of anatomical factors can cause the patella to track in a wrong way. Sometimes also the pressure in the patellofemoral joint is increased. Together can these issues stress the cartilage (chondromalacia patellae). This can cause inflammation that eventually leads to pain. have in cooperation with me created an Ebook, describing things much better than I am able to do - download this from free here

In case you would like a second opinion regarding your MRI or just your general knee situation, I do Skype consultations. The cost is 150 euro - email [email protected]

Is there a relationship between AKP 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.

Arthroscopic debridement

Arthroscopic debridement can occasionally be a solution. If the knee is locking or catching and there is no malalignment. (Meaning that the kneecap is tracking normally in the groove.)  Sometimes the cartilage on the rear side of the patella is uneven and the it might help to smoothen the cartilage. During the arthroscopy concomitantly plica resection can also be carried out (read here) , Arthroscopy is a very minor surgery and a skillful arthroscopist seldom makes things worse. Ask the surgeons about infrapatellar and lateral plica - if the surgeon ignores you, consider finding another surgeon.

Lateral retinaculum lengthening

If you are one of those troubled by chronic anterior knee pain it might be that you are having hyperpressure syndrome. In hyperpressure situations you typically have anterior knee pain, when your knee is bent for too long. This is mostly caused by a tight lateral retinaculum. (a kind of ligament that stabilise the patella - see image). Previously we did lateral releases, but today we try to avoid this. Instead we now use lengthening, since this gives better results. This is small surgery and seldom things get worse. Read more about kneecap tilt and the procedure below.

Tilt of your kneecap

When your retinaculum is tight, this can cause the patella to tilt. Often this tilt can be seen on an MRI scan. A lateral lengthening can in these situations often help to unload the cartilage forces and thereby reduce the pain. You should always undergo an MRI scan to rule out if the tilt is caused by trochlear dysplasia. If you have a lateral release in these cases, there is a risk of making the kneecap unstable, making it subluxate or even dislocate.

The medial and lateral retinacula (singular=retinaculum) help to stabilise the patella

Lateral lengthening technique

Lateral lengthening or release is a name of an operating technique. Here the outer ligament for the kneecap - which has two layers - is lengthened. You see the technique below, first is both layers splitted. Then they are cut in different places, so that the final result is a lengthening.

Lateral release reversal

Lateral release can sometimes result in medial patella instability. For the patient, this is a very troublesome situation. Luckily is lateral release a more and more seldom procedure. The clinical diagnosis is very easy if the surgeon gets the idea and know what to look for, nevertheless is this condition of medial instability often overlooked. The lateral release reversal is a relative simple surgical procedure, with reconstruction of the lateral retinaculum by using a part of the tratus ileotibialis tendon.

Anterior knee pain and tibial tubercle osteotomy

Anterior knee pain can in some cases be helped by unloading the patellofemoral joint via the procedure of transposition of the tibial tubercle (TTT), either medially (Elmslie Trillat osteotomy) or anteriorly (Fulkerson osteotomy) - again depending on the MRI findings. If the tibial tubercle is externally rotated, it can be a good idea to have this corrected.

Relative often anterior knee pain is caused by a high riding kneecap (patella alta). This can be corrected by doing a distalisation of the tibial tubercle, ,that is moving it downwards.

Fulkerson Osteotomy
Fulkerson Osteotomy candidate

Here you see light patellofemoral osteoarthritis and patella tilt and patellar overhang. The patient responded well on a Fulkerson Osteotomy and lengthening of the laterale retinaculum

Patella Alta

Patella Alta means a high riding patella. The result is that on bending your knee the kneecap reaches the trochlea groove too late. This increases tje wear of your cartilage on the rear of the kneecap. This causes pain. There is too little overlap on your cartilage between the patella and the groove for the kneecap. See figure on the right. This means that your pressure per square centimeter of cartilage is too high. Similar to high heeled shoes that spoils the flooring. When your patella is brought back into the trochlear groove, your pressure is actually reduced. This is in opposition what you as well as many surgeons may think. Read more here

The problem can be helped out with a distalisation of your tibial tubercle, efficiently pulling the kneecap down into a better position to engage in the groove at the right time.

The yellow demonstrate the overlap between the cartilage on the lower part of the patella and the cartilage on the trochlea groove. If the overlap is little will the pressure on the cartilage be high. Some might think that the pressure increase when the kneecap is pulled down - however it is just opposite.

Hoffa Fat Pad Impingement

Hoffa Fat Pad Impingement is a very common explanation for having anterior knee pain. However Hoffas Fat Pad Impingement is not a diagnosis, but something seen on MRI. Hoffa Fat Pad Impingement is cause by maltracking of the patella into the trochlear groove and in most circumstances is based upon Patella Alta or trochlear dysplasia.

Plica Synovialis The parapatellar plica and Infrapatellar plica is closely related to the Hoffa Fat Pad and often the pain is more related to those two plicaes and not the Hoffa. Read a little more about the plicaes here

Fad Pad Impingement - see more here

Corpus Hoffa is seen as orange

Anterior Knee Pain and increased femoral anteversion and/or increased tibial external rotation

A malrotated hip, making the knee go inwards (increased/decreased anteversion of the femur) can also lead to anterior knee pain due to increased forces on the joint. It needs to be ruled out by clinical examination and in severe cases by a CT scan or a special MRI scan. The malrotation can be corrected by a femoral derotational osteotomy. Beneath you see a figure demonstrating a left femur with severe increased internal rotation, causing the patella to dislocate or maltrack causing pain on the outer site of the kneecap. Sometimes the tibia is also involved having too much outer rotation and this also needs correction by a tibia derotational osteotomy - either alone or in combination with a femoral rotational osteotomy.

Chronic patellofemoral pain

This young woman had chronic anterior knee pain. I asked her to put the kneecaps in the front. She was not aware her legs were a different from others.

Chronic AKP

This young woman had chronic patellofemoral pain for years based upon 'miserable malalignment' also called 'torsional malaligment' She had been referred to a psychologist since she nothing was wrong. 

Increased femoral anteversion examination

This image is looking up the femur bone, from the knee up to the pelvis. The left femur (to the right of the image) shows that the shaft of the femur is rotated inwards compared to the other side. The this patient responded well on femoral rotation osteotomy.

Tibia varus osteotomy

In seldom cases can a person who are kneed be troubled by anterior knee pain and pain on the outer joint line. Here can an osteotomy that makes the leg straight be a good option.

Arthroscopic trochleoplasty 

Maybe your Anterior knee pain is caused by severe trochlear dysplasia. If you have trochlear dysplasia you are having too much bone in the groove containing the patella. The groove can be flat or dome shaped and consequently this can increase your pressure in the joint. By unloading the joint pressure by an arthroscopic trochleoplasty this can likely reduce the pressure and consequently your anterior knee pain. Please check this paper

Arthroscopic Trochleoplasty

Trochlear Dysplasia 

Before trochleoplasty

Imidiately after trochleoplasty

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

Patellofemoral resurfacing prosthesis

The Hemicap wave prosthesis in an inlay type. It is my experience that by reaching the knee from a lateral approach (outer site of the knee cap) you will get fast recovery and there is full weightbearing from day one. The surgery is performed as one day surgery and often you will be able to drive a car safely after 3-4 weeks. Read more here

Patellofemoral prosthesis Hemicap Wave

Below you see the Hemicap Wave prosthesis for severe patellofemoral osteoathritis. I have very good experience using the inlay prosthesis. The surgery is performed by one day surgery and you are allowed free range of movement and full weight bearing from day one. Read more here

Patellofemoral osteoarthritis

In cases of symptomatic osteoarthritis in the patellofemoral joint, several options exist. Some patient may have symptoms relief by a lateral lengthening, a lateral patella facetectomy, a TTT or a trochleoplasty or cartilage procedures such as microfracture or autologous cartilage transplantation and finally some patients needs to be treated by a patellofemoral prosthesis. Treatments with stemcells is on the exprimental level and right now we are testing adipose stem cell transplantations.

Anterior Knee Pain and Trochlear Dysplasia and osteoarthritis

In some special selected cases I have done a "Resection Arthrosplasty". This is in cases with severe anterior knee pain, trochlear dysplasia and arthritis. Alternative to a prosthesis, a new groove to the patella is made. Apparently this unloads the patella in such a degree that the pain diminishes significantly. Download the Editorial paper from the KSSTA journal by clicking below.  

Resection Arthroplasty