Retropatellar Pain Syndrome is also known as Patellofemoral Syndrome and Patellar Tendonitis/Jumper's Knee, but it should not be confused with another common knee ailment, Chondromalacia Patellae. Retropatellar Pain Syndrome is the painful result of physical and/or biomechanical changes to the knee joint – the area behind the knee where the patella (kneecap) and the femur (the thigh bone) meet. This anterior knee pain gets worse with physical activity and even prolonged sitting. Chondromalacia patellae is when the underlying patellar cartilage actually frays and is damaged or softened.
Three bones meet to form the knee : the thighbone (femur), the shinbone (tibia), and the kneecap (patella). When the leg moves, the kneecap slides along a shallow groove in the femur known as the trochlear groove. The joint is cushioned and smoothed by articular cartilage, which covers the surfaces of all the bones in the joint. Repeated abnormal stress of the joint, whether due to degeneration, injury, repeated excessive stress, abnormal alignment, or muscle weakness, can weaken and soften the articular cartilage, and put pressure on the kneecap. This is what causes the pain.
When afflicted with the condition, the patient's knee rubs against the trochlear groove, instead of gliding smoothly across it. The damage may range from a slight abnormality of the surface of the cartilage to a surface that has been worn away completely to the bone. Anterior knee pain can present a diagnostic challenge because of the complex anatomy of the knee.
- Overuse & Overload – Such as repeated weight-bearing impact
- Chronic Injury that has resulted in poor biomechanics
- Muscle weakness (of the vastus medialis)
- Prolonged sitting – This adds extra pressure between the patella and the femur during knee flexion.
- Poor form during exercise
- Biomechanical Problems – Including pronation (when the foot rolls inward while walking or running), supination (when the foot rolls outward while walking or running), and a large "Q Angle" (the angle formed by the thighbone and the patellar tendon).
Risk factors for Retropatellar Pain Syndrome include participation in high-impact sports like running, skiing, soccer, high-impact aerobics when there is faulty biomechanics, and trauma. The Q-Angle, the angle formed by the thighbone and the patellar tendon, can also a major factor. Quickly-growing teenage women most often have a more acute Q-angle than others and are thus at the highest risk group for developing the condition. Foot hyperpronation, a "wide" pelvis, old age and a knock-kneed or bow-legged stance also increase the risk for developing Retropatellar Pain Syndrome. Although many forms of muscle dysfunction are implicated in Retropatellar Pain Syndrome, weakness of the quadriceps and gluteal (butt) muscles plays a significant role in the development of this condition. Tibial torsion (abnormal twisting or rotation of the lower leg), obesity, a prior knee injury and family history can also lead to developing Retropatellar Pain Syndrome.