![]() In these patients the trochlea groove (femoral side) is misshapen and no longer matches the patella surface, increasing contact stresses and therefore resulting in early cartilage deterioration. In addition, patellofemoral arthritis is more common in patients with patellofemoral dysplasia. Shubin Stein notes, “Women tend to have higher Q angles than men, predisposing them to this condition that typically manifests during the third and fourth decades of life.”Īnother factor predisposing patients to patellofemoral arthritis is excessive hip anteversion, a condition in which the neck of the femur rotates too far forward in the hip socket, resulting in additional lateral (sideways) pull on the patella. This places abnormal stress on the patellofemoral joint, leading to progressive wear and tear of the soft cushion of the joint (cartilage). It tracks on a perfectly matched “rail” provided by the femur, much like a train on a track.Ī Q angle exceeding normal range indicates that the patella is being pulled laterally (to the side), and the joint is no longer congruent. ![]() The patella is imbedded in this “musculotendinous complex” that allows the patient to straighten the knee. The Q angle is determined between the quadriceps muscle running down the front of the thigh and its attachment through the patellar tendon below the knee joint. Based on the radiographs and MRI studies, your physician can determine if you carry anatomical factors that further predispose you to this condition: a radiographic parameter that is frequently found to be abnormal in patients with isolated patellofemoral arthritis is the “Q angle.” (Please Note: Many patients with osteoarthritis of the knee first develop the disease in the medial compartment of the knee and subsequently develop patellofemoral arthritis however, this article focuses on patients who develop arthritis limited to the patellofemoral joint.)Īccording to Beth Shubin Stein MD patellofemoral joint arthritis is more common in women than in men. “Patellofemoral arthritis is diagnosed when loss of cartilage is seen in the joint on x-rays or MRI and no other compartment of the knee is affected,” explains Friedrich Boettner, MD. This condition, which is more commonly seen in women, is characterized by pain in the front part of the knee (behind the patella, or kneecap) that typically worsens when the patient walks on inclined terrain, goes up and down stairs, knees, squats, and rises from the sitting position (while walking on level ground is often unaffected). However, in rare cases, arthritis may be isolated to the patellofemoral compartment. Knee arthritis frequently affects two or more compartments of the knee. While the first two compartments are the most important for the patient to walk on flat terrain, the third compartment (patello-femoral joint) is involved in activities like walking on inclined terrain, going up and down stairs, kneeling, squatting, and rising from the sitting position. The third compartment of the knee is formed by the kneecap (patella) and the front part of the femur and is called the “patello-femoral joint.”įigure 1: Diagram of knee anatomy, including the patello-femoral compartment, which is located behind the kneecap (patella). ![]() The knee joint is a complex structure with three main compartments that have individual functions and structures: the inner (medial) compartment and the outer (lateral) compartments are formed by the articulation (or joining) of the lowest part of the thighbone (femur) and the highest part of the shinbone (tibia). Knee arthritis is a condition that affects more than four million Americans annually, occurs when degenerative changes develop in the cartilage that lines the knee joint.
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