Arthrosis behind the kneecap or “retropatellar arthrosis” is a chronic, degenerative disease of a cartilage area in the knee. In addition to the tibial plateau and the deep part of the thigh bone, the kneecap also has a significant influence on joint function. It serves as a guide and fulcrum for the patellar tendon during all movements of the knee.
The patellar tendon runs from the large quadriceps muscle of the thigh via the knee joint to the tibia to allow the knee to be stretched. Due to various causes, the sensitive joint cartilage between the kneecap and the thigh bone can be injured, thus considerably restricting movement in the knee. The causes and manifestations of the disease are numerous, which is why the therapies must also be individual and the prognosis may vary.
The causes of arthrosis
Long-term wear and tear: Most cases of arthrosis behind the kneecap develop “idiopathically”. This means that there is no direct cause behind the damage to the cartilage, but rather a combination of various factors. In the large number of cases, it is a combination of overweight, age, previous injuries and excessive stress in sport or at work.
Patellar dysplasia: Just as often as idiopathic degeneration, patellar dysplasia or another congenital malformation of joint structures of the knee is behind the arthrosis. This is an asymmetrical deformation of the kneecap, which leads to a disturbance of the sliding function and uneven abrasion of the cartilage. Injury: In a small part of the arthrotic degeneration an injury is causal.
This can be injury to the patella itself or to the cruciate ligaments and menisci. Injuries as a cause of arthrosis are particularly common in young age. Surgical interventions after ligament injuries of the knee further increase the risk of arthrosis. Ligament instabilities: A rarer cause is the so-called “ligament laxity”. As a result, the kneecap can run outside the sliding bearing and lead to asymmetrical and uneven wear on the cartilage.
The X-B adjustment is a leg axis malalignment in which the knees are too far inward compared to the leg axis. When standing straight, the thighs and lower legs appear together in an X-shape. A straight leg axis causes the body weight to be distributed exactly to the centre of the knee joint.
However, with an X-bend, much of the weight is on the outer knee, which causes the cartilage to wear out more quickly and can cause pain. Osteoarthritis behind the kneecap is also greatly promoted by the leg axis malalignment. Most often the malposition is congenital, but also inflammations, tumours, previous injuries and disturbances in the hormonal balance can favour the development of bow legs.