Pictorial case study - Prepatellar bursitis: presentation, management and discussion

Dr Jean Watkins advises on the possible causes of prepatellar bursitis.

Tender swelling over the kneecap
Tender swelling over the kneecap

Presentation

For some years, this fit and healthy 40-year-old man had spent his working day on his knees, fitting carpets. In the past few months, he had been aware of a dull ache over his right knee, which had seemed to be aggravated by pressure and on flexion of the knee.

He had been wearing kneepads, using a soft mat and trying to avoid kneeling on that knee. However, he was alarmed to wake one morning with a large, tender, fluctuant swelling over the kneecap.

Management

A diagnosis of prepatellar bursitis was made. Prepatellar bursitis, also known as housemaid's knee, occurs as the result of inflammation of the bursa that lies over the patella; this leads to increased production of fluid within the bursa.

Most often caused by repetitive trauma to the knees, it was common in housemaids in the past, and is now often seen in carpet fitters and gardeners. It may also result from a recent traumatic injury.

Sometimes, it may be due to the deposition of crystals, as in gout, or associated with a systemic disease, such as rheumatoid arthritis.

If there is additional sepsis, due to local invasion of Staphylococcus aureus or streptococci, or to haematogenous spread from elsewhere, the patient may need urgent intervention with an antibiotic such as flucloxacillin 500mg four times a day, or if penicillin-sensitive, erythromycin 500mg four times a day. Referral is necessary in severe cases, if not responding, or in immunocompromised patients.

Discussion

A good history, and aspiration of the bursa using aseptic technique and examination of the fluid, will help to identify possible problems. In a simple bursitis, the fluid is clear - sepsis is indicated by cloudy fluid with pus, while crystals will be seen microscopically in cases of gout.

Aspiration should be carried out by an appropriately trained person, preferably before the patient starts taking antibiotics. A corticosteroid injection into the bursa can also be considered.

Most cases of prepatellar bursitis will resolve spontaneously with conservative treatment. Rest, icepacks and avoidance of further pressure or trauma to the knee are recommended, with an analgesic, such as paracetamol or an NSAID - unless this is contraindicated, as in patients with cerebrovascular or cardiovascular disease. Further trauma is to be avoided in order to prevent recurrences. This may be difficult in certain occupations, but protective kneepads and kneelers may be beneficial, as well as advice to avoid kneeling if possible.

Differential diagnoses
  • Rheumatoid arthritis
  • Gout
  • Septic arthritis or patella osteomyelitis - Traumatic injury
  • Cellulitis
  • Dr Watkins is a retired GP in Hampshire

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