Definition
Retropatellar arthrosis is a wear of the articular cartilage on the back of the patella, i.e. the kneecap. The joint here is the so-called “femoropatellar joint”, in which the kneecap (“patella”, facies articularis) and the femur (“femur”; facies patellaris) articulate together. The patella not only forms a part of the knee joint components but is also a kind of lever arm for the quadriceps (“Musculus quadriceps”), whose tendon extends over the patella.
The progression causes an extension of the lever arm and thus increases the torque. It is therefore possible to imagine that the patella can be subjected to extreme stress due to the communication with this large muscle. Such loads can disrupt the cartilage nutrition, which takes place via the synovial fluid, the so-called “synovia”. As a result, the cartilage loses substance and resistance, resulting in joint wear and tear, i.e. arthrotic phenomena. This can lead to massive pain behind the kneecap.
Symptoms
Typical symptoms that occur in patients with retropatellar arthrosis are pain when climbing stairs, walking down slopes and getting up from a squatting position, especially after long periods of sitting. The pain is usually localized in the front area of the knee joint. It is often a gradual process that begins with slight pain and can lead to a lack of resilience, inflammation, and even to restricted mobility with severe pain.
Retropatellar arthrosis can result in a reduced load-bearing capacity of the knee joint, as incorrect pressure loads have been applied previously. The femoropatellar joint reacts to this by reducing the strength of the thigh muscle in addition to the wear and tear on the patella. However, this means that the knee joint, especially the back of the patella, is subjected to more stress.
This is because the quadriceps has an important stretching function at the knee joint, and thus the wear and tear is provoked even more. The insidious pain sometimes comes along with a cracking sound and a feeling of instability. Patients sometimes also report teething problems, especially after prolonged sitting, i.e. when the knee was bent. As an accompanying symptom, the joint can become inflamed due to the overloading, so that swelling and reddening may occur in addition to the pain. In summary, an imbalance between load and capacity of the knee or the femoropatellar joint is responsible for the arthrosis.
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