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Causes and symptoms of kneecap problems

The patellofemoral joint, which connects the kneecap to the thigh bone, must withstand forces up to eight times your body weight when you walk stairs, descend inclines, jump, land or squat. It is an area sensitive to overloading, which can lead to cartilage damage and osteoarthritis (at a later age). Usually this can be treated without surgery. In extreme cases an arthroscopy or a knee replacement can be necessary.


Sometimes symptoms start at a much younger age (12 to 25), because of a congenital deformity of the MPFL ligament that should normally keep the kneecap in its place. In such cases a surgical kneecap alignment is usually the only solution.

Globally speaking, there are three types of kneecap problems:

1. Anterior knee pain


Anterior knee pain - or pain at the front of the knee joint - is common, especially in young girls and women (12-25). Usually the immediate cause is unclear. Further research (medical imaging with radiography, NMR scan) tends not to show a lot of obvious deviations in the joint. Treatment is therefore often strictly non-surgical.

In our experience, the symptoms usually seem to find their cause in overloading due to poorly performing muscle groups around the lower back, hip, pelvis and thighs. The best solution lies in a detailed treatment plan based on thorough research by the knee surgeon, along with personal advice, targeted physiotherapy and possibly dietary supplements. Although the complaints are often chronic, they tend to disappear spontaneously after the age of 25.

2. Arthritis


Ostheoarthritis or cartilage wear is widely regarded as an aging disease, but it can also affect younger people, especially around the kneecap. The clearest symptom is a vague pain at the front of the knee, getting worse when descending stairs or even when sitting for a long time with bent knees.


Cartilage injuries around the kneecap (patella) and kneecap groove (trochlea) are always caused by a clear trauma, like a fall on the knee or a kneecap lucation (see below: "Stablity problems"). Usually small trauma causes accelerated arthritis of the kneecap compartment. These microtraumata are often accumulations of small lesions due to minimal but prolonged overloading, eventually resulting in cartilage damage. This is why most cartilage injuries only become clear a bit later in life (around 35-45).

Treatment of cartilage injuries around the kneecap is usually non-surgical: physiotherapy and infiltrations with hyaluronic acid or cortisone tend to suffise. In specific cases, surgery may be advised in the form of an arthroscopy (keyhole surgery), cartilage treatment or relocation/relief of the kneecap (tuberosity transposition). In the case of advanced osteoarthritis, knee replacement surgery may be necessary. These patients tend to be slightly younger (50-60) than the typical prosthetis patient (65+).

3. Stability problems


Patella luxation (dislocated kneecap) and instability (the feeling of a collapsing knee joint) usually occur for the first time at a young age (12-25). The underlying cause is usually an anatomical, hereditary deviation in the shape of the kneecap and/or the trochlea, the groove at the end of the femur through which the kneecap should slide. The latter phenomenon is called trochleodysplasia.

Another possible abnormality is patella alta: the kneecap being positioned too high with respect to the femur (e.g. because the kneecap ligament is too long). If this ligament is attached too laterally, it could also cause patella luxations. Deviations in the rotation of the femur (hip anteversion) and tibia are other possible causes of anatomically overloaded kneecap joints. Often, we see a combination of the above deviations. A correct and thorough diagnosis is therefore essential in the treatment of stability problems. Exceptionally, a luxation can also occur in a person without risk factors, e.g. during a sports incident with direct trauma.


The more severe the abnormalities in the knee, the earlier the first luxation will occur. The younger you are when the first luxation occurs, the greater the chance that it will happen again. This can be problematic, because every luxation results in permanent damage to the kneecap joint. More specifically, it affects the cartilage and tears the MPFL (Medial Patello-Femoral Ligament), a small ligament on the inside of the knee which connects the kneecap to the femur.

The good news: reconstructing the MPFL surgically not only restores stability, but often leads to spontaneous healing of the damaged cartilage, which does therefore not need to be treated separately. That's why these days surgical treatment of patella luxation is mostly focused on MPFL reconstruction (see below), with excellent results.

What is an MPFL reconstruction?

For the reconstruction of the MPFL ligament, a tendon from your knee is repurposed to stabilize the kneecap. This new link between kneecap and thigh bone is four times stronger than the original ligament. In most cases, this fixes the problem for life.

It does sometimes occur that the kneecap is aligned too high or too much to the side to be adequately corrected using this technique. In that case, additional surgery is required. The best solution is evaluated for each case individually and discussed with the patient. This so-called "tuberosity transfer surgery" affects the bone and thus requires a longer rehabilitation period.

Orthopedic surgeon - specialized in the treatment of knee injuries

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