Background Partial Achilles tendon ruptures are not always easy to diagnose. A history including a sudden onset of pain and/or relative weakness in plantar flexion force is an indicator. The most loaded side of the Achilles tendon is the dorsal side (skin side).

Objective The aim of this study was to evaluate the ultrasound (US) and colour Doppler (CD) findings in patients with a suspected partial rupture in the Achilles tendon.

Materials and Methods Seventeen patients (16 men and 1 woman) with a mean age of 36 years (range 23–71 years) were examined clinically and by US+CD because of mid-portion Achilles tendon pain. There was an acute onset in 14 of 17 patients, and all had painful weakness during tendon loading activity.

Results In all patients, the US examination showed a partial Achilles tendon rupture, presented as a disrupted dorsal (skin side) tendon line and an irregular tendon structure mainly located in the dorsal and mid-tendon. The size of the rupture varied from 1/3 to 2/3 of the tendon thickness. In the dorsal part of the tendon, corresponding to the region with disrupted tendon line and irregular structure, CD examination showed high blood flow—most often of a longitudinal character. Six of the patients were surgically treated, and macroscopical examination verified the US findings showing disruption on the dorsal side and a partial rupture in the dorsal and mid-tendon.

Conclusions US and Doppler examination can be helpful tools to diagnose partial mid-portion Achilles tendon ruptures. The characteristic findings of a disrupted dorsal tendon line and high blood flow in the structurally abnormal dorsal tendon indicate a partial rupture.