The patellofemoral joint

The patella keeps popping out – Problems affecting a child’s patellofemoral joint

The patellofemoral joint is a part of the knee joint and consist of the kneecap (lat. patella) and its groove on the thigh bone (lat. trochlea). A fall while skiing with external rotation of the foot, the foot firmly planted on the ground with the body rotating away, and slight knock knee stress (genu valgum) (while dancing or playing indoor sports) are classic causes of one’s first patella dislocation, i.e. the kneecap pops out for the first time. If the kneecap snaps back into place on its own, this injury is often misdiagnosed. If it does not, the situation is usually perceived as very dramatic due to the apparent deformity and the severe pain.

It is estimated that the kneecap pops out once in 43 out of every 100,000 children. However, the risk of this happening again (repeated patellar dislocation) is over 60%! Since any dislocation of the patella carries the risk of cartilage damage in the patellofemoral joint, further episodes of instability should be avoided. The risk of re-injury can be estimated based on various risk factors, which are determined during a clinical examination and measured via x-ray and MRI.

Depending on the result, either conservative management or surgery are recommended. It is important to note that this is a risk assessment and the recurrence of patellar dislocation is not due to inadequate training. If the cartilage is already injured, surgical treatment is more likely to be recommended. Depending on the patient’s age and stage of development, various different surgical procedures can be considered.