Prepatellar Bursitis

Abstract

A bursa is a small sac of fibrous tissue with a thin synovial lining that is filled with fluid. Numerous bursae are found in the body, around joints and in places where ligaments and tendons pass over bones. They can also form in other places as a response to unusual pressure or friction. Generally, bursae help to reduce friction and allow maximal range of motion around joints. Bursitis is inflammation within a bursa. The inflammation leads to an increase in synovial fluid production and causes the bursa to swell. There are four bursae located around the knee joint. They are all susceptible to bursitis but the prepatellar bursa is most commonly affected. Less frequently, the infrapatellar and deep patellar bursae can become inflamed [1]. The prepatellar bursa is located superficially on the anterior aspect of the knee between the skin and the patella. The bursa does not communicate with the knee joint and the knee joint itself is normal in prepatellar bursitis. Aetiology Prepatellar bursitis may occur due to: Acute trauma: fall/direct blow on to the knee. Recurrent minor injury: occurs after long periods of time spent kneeling forwards and putting pressure on the patella. Historically, this was typical of housemaids who spent long periods of time on their knees scrubbing floors; hence, the term 'housemaid's knee'. It is now more commonly seen in tradesmen-eg, carpet fitters, concrete finishers, roofers. Infection: pyogenic prepatellar bursitis is common in children. It may be mistaken for septic arthritis of the knee. Staphylococcus aureus is the usual causal agent. There is usually a history of a break in the skin prior to its onset. A co-existing inflammatory disease: for example, synovitis related to rheumatoid arthritis. A crystal-depositing condition: prepatellar bursitis is more common in people with gout or pseudogout.