PFPS is a blanket term for various conditions involving the front part of the knee joint, immediately around the patella. The underlying causes can range from malalignment such as patellar tracking disorder up to damaged cartilage. The latter includes patellar chondropathy, chondromalacia and, in the worst-case scenario, retropatellar osteoarthritis (arthrosis of the kneecap).

Chondropathy is the umbrella term for pathological changes in the articular cartilage. These changes can in turn be triggered by various underlying causes of a traumatic, degenerative or inflammatory nature. Chondromalacia is a degenerative disorder affecting the joint cartilage. The cartilage softens, often due to overuse or an injury. This can lead to a loss of cartilage. However, chondropathy and chondromalacia can be reversed in many cases.

Retropatellar osteoarthritis is one of the most severe long-term outcomes. Many people over the age of fifty experience this sort of wear and tear to their kneecaps and cartilage. Arthrosis of the patella is often triggered by an injury, e.g., if the kneecap is broken or dislocated, or after a cruciate ligament injury, or due to a patellar tracking disorder. If your hip and thigh muscles are weak or if your kneecap is not in the right position – for example, too high, too low, or too far to one side – you are more likely to be affected by resulting wear and tear.

The kneecap (patella) is located above the knee joint and moves most when you bend your knee or extend your leg. It then glides along a special groove on the thigh bone as if on a track. If the patella is misaligned or too much strain or weight is placed on the joint, it can slip out of place, causing irritation between the kneecap and the knee joint. In most cases, the patella slips out of place laterally, in other words, to the outer side of the knee joint. This will generally happen when your leg is bent at an angle between 10° and 30°, because the kneecap is not supported as strongly by bones in this range. Ultimately, this malalignment will result in pain and can lead to patellofemoral pain syndrome or even to dislocation of the patella. The patella is less likely to slip out of place when your knee joint is bent at an angle greater than 30°, because it then rests more firmly in the groove.

Generally speaking, anterior knee pain develops gradually and gets worse particularly when you place external strain on your knee by engaging in sports, climbing stairs, sitting for long periods or bending your knee. When you rest your knee, the pain often subsides again. Given the right therapy, the prognosis for the disease progression is excellent. Sometimes, the anterior knee pain disappears all by itself.