Magnetic resonance imaging and incidental findings of lateral ankle pathologic features with asymptomatic ankles.

We prospectively evaluated 102 magnetic resonance imaging (MRI) examinations in 100 patients with asymptomatic lateral ankles. The patients were undergoing MRI for other ankle pathologic features, including medial ankle, posterior ankle, soft tissue masses, or Achilles tendon pain. No patient had had a recent lateral ankle injury or any surgery. Whether the anterior talofibular ligament, calcaneofibular ligament, and peroneal tendons were intact, torn, or absent was recorded.

The average patient age was 46.4 years. Of the 100 patients, 67 (66%) had no history of a lateral ankle sprain, and 35 (34%) had sustained 1 or more sprains in the remote past. Also, 72 had an intact anterior talofibular ligament (71%), 90 had an intact calcaneofibular ligament (89%), 67 had intact peroneus brevis tendons (66%), and 68 (67%) had intact peroneus longus tendons. One accessory peroneal tendon was noted. Approximately 30% of asymptomatic patients undergoing MRI had abnormal anterior talofibular ligaments and peronei.

Because the published data show that functional rehabilitation is successful for 90% of symptomatic lateral ankle patients, caution is warranted if choosing surgical treatment on the basis of the MRI findings alone.