RECTUS FEMORIS MUSCLE TEAR APPEARING AS A PSEUDOTUMOR

Quadriceps muscle strains are common sporting injuries, but occasional ly a tear of the rectus femoris muscle can appear as a soft tissue mas s of the anterior thigh with or without a significant history of traum a. Between 1992 and 1996, seven patients were referred to the Orthopae dic Oncology Unit at Waiter Reed Army Medical Center with an unexplain ed soft tissue mass of the thigh. Three were active duty soldiers, thr ee were military dependents, and one was a retired serviceman. All pat ients were men, and the mean age was 32 years (range, 15 to 73). A pal pable, mildly tender mass was confirmed on clinical examination. Labor atory studies and plain radiographs were normal. Magnetic resonance im aging showed an obvious, but often ill-defined, lesion at the musculot endinous junction of the rectus femoris muscle. Four patients subseque ntly underwent a tissue biopsy to rule out a soft tissue sarcoma. Hist ologic studies showed fibrosis, degeneration of muscle fibers, and chr onic inflammatory cells with no evidence of malignancy. A chronic rect us femoris muscle tear can mimic a soft tissue tumor or sarcoma and ne eds to be excluded in the differential diagnosis. These tears may occu r acutely or may represent an overuse injury caused by repeated microt rauma. Careful history taking, physical examination, and selective rad iographic studies, specifically magnetic resonance imaging, can confir m the diagnosis of muscle tear and full functional recovery can be ant icipated.