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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.
A combination of factors may contribute to the development of patellar tendinitis, 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 greater waist circumference or 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.
- Malalignment of your leg bones. 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.
- Hudgins TH. Jumper's knee. In: Frontera WR, et al. Essentials of Physical Medicine and Rehabilitation. 2nd ed. Philadelphia, Pa.: Saunders Elsevier; 2008. http://www.mdconsult.com/das/book/body/171922449-6/918424682/1678/67.html#4-u1.0-B978-1-4160-4007-1..50066-3--cesec4_1064. Accessed Nov. 18, 2009.
- Choi L. Overuse injuries. In. DeLee JC, et al. DeLee and Drez's Orthopaedic Sports Medicine. 3rd ed. Philadelphia, Pa.: Saunders Elsevier; 2009. http://www.mdconsult.com/das/book/body/171922449-6/918424682/2079/17.html#4-u1.0-B978-1-4160-3143-7..10014-4--s0125_1247. Accessed Nov. 18, 2009.
- Miller TT. Common tendon and muscle injuries: Lower extremity. Ultrasound Clinics. 2007;2:595.
- Azar FM. Traumatic disorders. In: Canale ST, et al. Campbell's Operative Orthopaedics. 11th ed. Philadelphia, Pa.: Saunders Elsevier; 2007. http://www.mdconsult.com/das/book/body/171922449-6/0/1584/351.html?tocnode=55688624&fromURL=351.html#4-u1.0-B978-0-323-03329-9..50049-0--cesec7_2498. Accessed Nov. 18, 2009.
- Khan K, et al. Overview of the management of overuse (chronic) tendinopathy. http://www.uptodate.com/home/index.html. Accessed Nov. 18, 2009.
- Cucurulo T, et al. Surgical treatment of patellar tendinopathy in athletes. A retrospective multicentric study. Orthopaedics & Traumatology: Surgery & Research.2009;95:78.
- Rees JD. Management of tendinopathy. The American Journal of Sports Medicine. 2009;37:1855.
- James SLJ, et al. Ultrasound guided dry needling and autologous blood injection for patellar tendinosis. British Journal of Sports Medicine. 2007;41:518.
- Laskowski ER (expert opinion). Mayo Clinic, Rochester, Minn. Nov. 23, 2009.
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