Painful ankle region in rheumatoid arthritis. Analysis of soft-tissue changes with ultrasonography and MR imaging

To establish the diagnostic usefulness of ultrasonography (US) and MR imaging in patients with rheumatoid arthritis (RA) suffering from prolonged pain in the ankle region, where plain radiography did not demonstrate any changes.

Seventeen patients were studied with 0.1 T MR imaging and with high-frequency US. Talocrural and subtalar joints (including talonavicular joints), and medial, lateral, and extensor tendons and their synovial sheaths were examined by MR and US.

Abnormal findings were found by MR imaging and US in altogether 76% of the patients, by MR alone in 53%, and by US alone in 59%. In 41% of the patients, lesions were demonstrated only by one method. Talocrural and subtalar joints were the most often affected sites (41% each), followed by the peroneus tendon (23%). In the joints, the abnormal findings were interpreted as synovitis; in the tendon areas, mostly as tenosynovitis. MR and US were highly significantly concordant (p < 0.0001), but correlation with clinical features was poor.

In patients with pain in the ankle region, US and MR imaging can contribute to the diagnosis and localization of the abnormality when the plain radiography is normal. Easily available and inexpensive US can be recommended as the first imaging method after plain radiography. Some divergence seems to exist between US and MR, and in complicated cases both methods are recommended.