Risk factors

A combination of factors may contribute to the development of patellar tendinitis, including:

• Physical activity. Running and jumping are most commonly associated with patellar tendinitis. Sudden increases in how hard or how often you engage in the activity also add stress to the tendon, as can changing your running shoes.
• Tight leg muscles. Tight thigh muscles (quadriceps) and hamstrings, which run up the back of your thighs, can increase strain on your 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.
• Chronic illness. Some illnesses disrupt blood flow to the knee, which weakens the tendon. Examples include kidney failure, autoimmune diseases such as lupus or rheumatoid arthritis and metabolic diseases such as diabetes.