Osteoid osteoma. Distant, periarticular, and subarticular lesions as a cause of knee pain.

Osteoid osteoma, a benign osteoblastic tumour comprised of osteoid and atypical bone, is a well-known entity. However, clinical diagnosis may be delayed, especially when the pain is referred to a nearby joint. This paper reports a series of 11 cases occurring in physically active patients in whom the diagnosis was delayed because of pain referral to the knee. The mean duration from the onset of symptoms to diagnosis of osteoid osteoma was 20 months (range 3 to 48 months). Review of these 11 lesions indicates that they can be classified on the basis of their anatomical location: (a) distant to the knee; (b) periarticular; or (c) subarticular (intraarticular). It should be noted that initially only 5 of the 11 cases displayed characteristic x-ray findings; in the remaining 6 cases, diagnosis was dependent on positive 99mTc radionuclide bone scans, tomograms, and computerised tomography scans. Of the 9 patients who underwent surgical resection of their lesions, all had complete relief of symptoms and all continued to be asymptomatic at follow-up evaluations.