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ABSTRACT

Prepatellar bursitis is a well known adult injury, especially within certain occupations such as carpet layers, roofers, coal miners and individuals who scrub floors while kneeling.1  It is also seen in adolescents and adults engaged in sports with repeated knee trauma such as wrestling and occasionally volleyball. The following is a report of prepatellar bursitis in a ten year old male whose mechanism of injury was not immediately evident.

INTRODUCTION

Prepatellar bursitis is a common injury found mainly in adults. The following case is about a novel method of acquiring this disorder which is illustrative of old, well known disorders induced by new types of activities.

REPORT OF CASE

A ten year old boy was brought by his mother for evaluation of a “sore” right knee. It had been painful for the past three weeks and the child had been limping for the past week. The pain was initially intermittent and began 3-4 days after Christmas. Neither the mother or child were able to recall any initial trauma to the knee. The child was not involved in any formal sports program.

Physical exam was remarkable for a mild swelling in the infrapatellar region of the right knee. The area of swelling was tender, but not erythematous or hot. There was no pain with varus or valgus stress. Posterior and anterior drawer tests were negative. There was no joint line tenderness. There was no pain with apprehension testing or grind. The knee had a full passive range of motion.

Following the physical exam the mother was questioned about any activities the child may engage in while kneeling. She said her son would kneel while watching television and playing video games. The mother said he did not watch much television, but that he did kneel in front of television two to three hours per day playing video games.  While playing he is quite active and bounces on his knees. He received several new games at Christmas and his playing time increased.  Symptoms began several days later.

The differential diagnosis includes Osgood-Schlatter syndrome, osteosarcoma, connective tissue disorders such as juvenile onset rheumatoid arthritis and patellar fracture. Radiographs of the knee were obtained and were negative for any osseous pathology. Serum blood tests of anti nuclear antibodies, rheumatoid factor and RPR were negative. A complete blood count was normal as was a sedimentation rate.

The child was placed on 200 mg of ibuprofen three times per day with meals. He was instructed to ice the knee four times per day for 20 minutes at a time. The child was told not to kneel in front of the television anymore but should sit in a chair to play his video games or watch television. He was kept out of physical education class for two weeks. The mother was spoken to three weeks from the initial office visit. She denied any continued problems or pain with her son’s knee.

DISCUSSION

The pre patellar bursa is an anatomic structure located of the knee the skin and the patella and patellar ligament. It is a true bursa and thus has a thin synovial lining.2  Prepatellar bursitis has several different causes including trauma with hemorrhagic and inflammatory subtypes, crystal deposition, and infection (septic bursitis).3  Inflammatory bursitis can be broken down into trauma and metabolic causes.

Trauma related inflammatory bursitis arises from a single episode of acute trauma or repetitive micro trauma to the prepatellar bursa. This results in vasodilation, extravasation of fluid and proteins. This causes erythema and swelling. Bursitis secondary to metabolic causes like rheumatoid arthritis, scleroderma, spondyloarthropathies, hypothyroidism and syphilis can present in a similar way without a history of trauma.3

The other trauma related prepatellar bursitis is hemorrhagic bursitis. Hemorrhagic bursitis is normally caused by a direct blow to the knee resulting in bleeding into the bursa from surrounding tissues. This causes swelling of the bursa which results in pain and decreased movement of the knee joint.3

Crystal deposition causing prepatellar bursitis would be unusual in a child.4  In an adult, a sample of bursal  fluid should be obtained and analyzed for crystals. Several different conditions can cause crystal induced prepatellar bursitis. These include gout, with a finding of monosodium urate crystals in the aspirate. With tuberculosis or rheumatoid arthritis, one may find cholesterol crystals in the aspirate. With degenerative arthritis or hyper(hypo)thyroidism, calcium pyrophosphate crystals would be found in the aspirate. Calcium oxalate crystals in the aspirate are associated with renal dialysis. Calcific bursitis with chronic inflammation should be considered if hydroxyapatite crystals are found in the aspirate.3

Septic prepatellar bursitis generally results from seeding of the bursa with bacteria following direct trauma to the anterior knee.5 The prepatellar bursa is one of the most common sites for septic bursitis.3 The causative organism in up to 90% of cases is Staphylococcus aureus or Staphylococcus epidermidis. The other prevalent organisms are streptococcal species and mycobacterium species.3 The usual clinical findings include burial tenderness in 90% to 100% of patients, an abrasion in 50% of patients, swelling and peribursal cellulitis in almost all patients. Fever is present in 40% to 90% of cases.5 The best way to diagnose septic bursitis is to aspirate fluid from the affected bursa. If there is any doubt differentiating between a septic versus non-septic bursitis the aspiration must be done. The distinction is not always clear-cut based on history and physical exam alone. The aspirated fluid should be cultured, gram stained, have a cell count done, and be analyzed for aspirate glucose which is then compared to serum glucose. Leukocyte counts may go as high as 300,000 cells per microliter. Infection can be so devastating that suspicion of infection should be raised with any leukocyte count greater than 1,500 cells per microliter. Glucose in the aspirate should be less than 50% of the serum value to suggest septic bursitis. The gross appearance can be purulent, serosanguineous, or straw colored.5

Treatment of the various types of of prepatellar bursitis has some common elements as well as cause specific elements. The general treatment for non-septic prepatellar bursitis may include aspiration of the bursa for comfort followed by steroid injected into the bursa. The other cornerstones of treatment are padding or bracing to protect the bursa, rest, ice, compression and elevation, non-steroidal anti-inflammatory medications and the above mentioned injectable steroid or possibly with a burst of oral steroid for a short period of time prior to using the non-steroidal anti-inflammatory medications.3  Crystal induced bursitis may also be treated as above. It is essential to determine and treat the underlying cause of the crystal formation.

Septic bursitis must not be treated with injectable or oral steroids. It requires antibiotics that treat Staphylococcus aureus. The initial treatment is hospitalization and intravenous antibiotics.5  Surgery is reserved for cases that are refractory to treatment or recur multiple times. A bursectomy could then be performed.3

COMMENT

Prepatellar bursitis is a relatively common injury. Persons with an initial, isolated case of prepatellar bursitis do very well with conservative treatment such as rest, ice, compression, and anti-inflammatory medications. The history of trauma helps shed light on the underlying etiology which helps guide treatment as was illustrated in this case. Each subsequent injury is less amenable to the above conservative treatment and increases the risk for surgery.1  It is important to educate patients who have been treated for prepatellar bursitis on ways to avoid re-injuring the prepatellar bursa. This education would include emphasizing the use of adequate knee padding for individuals in jobs or sports that require kneeling and/or frequent impact trauma to the knee such as occurs in wrestling. The most important aspect of evaluation and treatment of patients with prepatellar bursitis is to aspirate any prepatellar bursa suspicious for infection.

REFERENCES

  1. Mysnyk MC, Wroble RR, Foster DT, Albright JP: Prepatellar bursitis in wrestlers. The American Journal of Sports Medicine 1986;14(1):46-54.
  2. Bellow EM, Sacco DC, Steiger DA, Coleman PE: Magnetic resonance imaging in “housemaids knee” (prepatellar bursitis). Magnetic Resonance Imaging 1987;5:175-177.
  3. Butcher JD, Salzman KL, Lillegard WA: Lower extremity bursitis. American Family Physician 1996;53(7)2317-2324.
  4. Primer on Rheumatic Diseases, 10th Edition, ed. Schumacher HR,JR; Arthritis Foundation; Gout,pg.209.
  5. McAfee JH,Smith DL: Olecranon and prepatellar bursitis diagnosis and treatment. Western Journal of Medicine 1988;149:607-610.
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