Ultrasound (US) is an accurate means to assess ankle tendons. In the anterior ankle, US is able to identify the rupture or the distal tendinopathy of the tibialis anterior tendon. Injuries to the peroneal tendons are commonly encountered in clinical practice and include tenosynovitis, tendinosis, rupture and instability. The US diagnosis of peroneal tendon instability is based on detection of the tendons lateral to the distal lateral malleolus. Longitudinal splits of the peroneus brevis arise at the distal end of the lateral malleolus, extending distally and proximally from there. When the peroneus brevis is split longitudinally, it can assume a "horseshoe" shape at US examination with the peroneus brevis that partially envelops the longus. In the medial ankle, the tibialis posterior is the most common injured tendon. US has also proved to be an effective means to identify tendon changes related with serous and hypertrophic tenosynovites. US can identify focal areas of synovitis around the posterior recess of the ankle joint and abnormalities of the flexor hallucis longus tendon. Stenosing tenosynovitis of the flexor hallucis longus occurs as either the result of focal areas of synovitis or fibrosis within the tendon sheath that causes blockage of normal synovial fluid flow, or in association with the os trigonum syndrome. In the posterior ankle, the main abnormalities recognized in patients with Achilles tendinosis are tendon swelling and textural abnormalities with intratendinous focal hypoechoic areas. Hypoechoic changes in the proximal two-thirds of the Achilles tendon may be diffuse or confined to its medial fibers. On the other hand, US abnormalities in the distal Achilles tendinopathy more commonly involve the deep portion of the Achilles tendon, often in association with retrocalcanear bursitis. The complete rupture of the Achilles tendon appears as a focal defect between the torn tendon edges. If the tendon ends abut one another without an intervening gap, dynamic scanning may help to distinguish partial from complete tears.