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Causes
By Mayo Clinic staffPatellar tendinitis is a common overuse injury. It occurs when you place repeated stress on your patellar tendon. The stress results in tiny tears in the tendon, which your body attempts to repair. But as the tears in the tendon become more numerous, your body can't keep up, causing the inflammation in your tendon to worsen.
Doctors aren't certain what causes patellar tendinitis. It's believed that a combination of factors could be involved, including:
- Intensity and frequency of physical activity. Repeated jumping is most commonly associated with patellar tendinitis. Sudden increases in the intensity of physical activity or increases in frequency of activity also put added stress on the tendon.
- Being overweight. Additionally, being overweight or obese increases the stress on the patellar tendon, and some research suggests that having a higher body mass index may increase the risk of patellar tendinitis.
- Tight leg muscles. Reduced flexibility in your thigh muscles (quadriceps) and your hamstrings, which run up the back of your thighs, could increase the strain on your patellar tendon.
- Misalignment of your leg. The way your leg bones line up could be off slightly, putting strain on your tendon.
- Raised kneecap (patella alta). Your kneecap may be positioned higher up on your knee joint, causing increased strain on the patellar tendon.
- Muscular imbalance. If some muscles in your legs are much stronger than others, the stronger muscles could pull harder on your patellar tendon. This uneven pull could cause tendinitis.
Patellar tendinitis is commonly known as jumper's knee. However, because anyone can suffer from patellar tendinitis, whether a frequent jumper or not, this term may be misleading. Terms that doctors sometimes use to describe recurring patellar tendinitis that causes further degeneration of the patellar tendon include patellar tendinopathy and patellar tendinosis.
