Osteochondritis dissecans has been reported to affect the ankle as the third most common joint, after the knee and the elbow.1 A 26-year-old housewife presented with chronic ankle pain for 3 weeks duration with intermittent swelling after exertion, without any history of trauma. Based on the clinical picture and results of the blood investigations such as erythrocyte sedimentation rate (26 mm first hour, Westergren method) and C reactive protein (weakly positive), the patient was diagnosed with seronegative monoarticular rheumatoid arthritis and treated with non-steroidal anti-inflammatory drugs (NSAIDs) and sulfasalazine, but without much relief. Plain radiography was unable to show the lesion (figs 1 and 2), and the diagnosis was picked up only on magnetic resonance imaging (MRI) (figs 3 and 4). The patient underwent arthroscopic debridement of the lesion. At 2 years follow-up, the patient has returned to her routine activities.

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Figure 1

Anteroposterior radiograph of the patient’s ankle, showing a normal talar dome.

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Figure 2

Lateral radiograph of the patient’s ankle, also showing a normal talar dome.

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Figure 3

Sagittal magnetic resonance image (MRI) of the talus showing an osteochondral lesion on the posterior aspect of the talar dome.

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Figure 4

Coronal MRI image of the talus showing an osteochondral lesion on the medial aspect of the talar dome.

Delayed diagnosis and treatment of osteochondritis dessicans of the ankle can result in irreversible articular damage leading to significant morbidity.2 Awareness of the condition and a high index of suspicion on the part of family physicians is important in order to make an early diagnosis. Findings on plain x ray may be unremarkable and MRI is the investigation of choice.3 Early surgery is the key to good results.