Rare localization of osteoid osteoma in the patella

Excerpt

A 17-year-old girl had had right anterior knee pain for 2 years, which was initially believed to be due to chondromalacia patellae. After ineffective conservative management, arthroscopy was undertaken, but was normal. The pain worsened, especially at night. Repeated radiographs revealed a small radiolucent lesion with central mineralization in the upper part of the patella (Fig. 1a). Despite the absence of a typical sclerotic rim, the appearances were strongly suggestive of osteoid osteoma. The lesion could hardly be seen on the AP view. ^99mTc-MDP bone scintigraphy demonstrated significantly increased uptake in the right patella surrounded by less intense uptake—the double density sign characteristic of osteoid osteoma (Fig. 1b) [1, 2] Fluoroscopically controlled en-bloc resection of the lesion was performed. Osteoid osteoma was confirmed histologically. The patient is asymptomatic after 2 years of follow-up.

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