The ruptured achilles tendon is examined by ultrasonography. If the overlap of the tendon ends is less than 25 % or the tendon is elongated 7 % or more the patient receives conventional open operative treatment. The tendon is sutured with double fiberwire size 2 a.m. Kessler under prophylactic Dicloxacillin 2 g and in local anesthesia or alternatively popliteal or spinal block. The injured leg is placed in a circulated below the knee cast after surgery. The ankle is held at maximal plantar flexion. Weight bearing is not allowed. After 3 weeks the cast is removed and the injured leg is transferred to a functional brace with 3 heel wedges. The patient will follow standard functional rehabilitation and the follow-up evaluations.

For the patients allocated to non-operative treatment the injured leg is placed in a circulated below the knee cast from the time of the first appointment in the Outpatients Department. The ankle is held at maximal, unforced plantar flexion. Weight bearing is not allowed and the patient should walk with the aid of crutches. After 3 weeks from initiated treatment in the Emergency Department the cast is removed in the Outpatients Department and the injured leg is transferred to a functional brace (Walker boot) with 3 heel wedges promoting 20 degrees plantar flexion over the ankle. The patient will follow standard functional rehabilitation and the follow-up evaluations.

The tendon is sutured with double fiberwire size 2 a.m. Kessler under prophylactic Dicloxacillin 2 g and in local anesthesia or alternatively popliteal or spinal block. The injured leg is placed in a circulated below the knee cast from the time of the first appointment in the Outpatients Department. The ankle is held at maximal, unforced plantar flexion. Weight bearing is not allowed and the patient should walk with the aid of crutches. After 3 weeks from initiated treatment in the Emergency Department the cast is removed in the Outpatients Department and the injured leg is transferred to a functional brace (Walker boot) with 3 heel wedges promoting 20 degrees plantar flexion over the ankle. The patient will follow standard functional rehabilitation and the follow-up evaluations.

The most proximal border of the calcaneus and the most distal point of the musculotendinous junction of the medial gastrocnemius muscle is identified and marked on the skin. These two points on the un-injured leg defines the original length of the total Achilles tendon [1]. The difference in length between the injure and the un-injured leg determines elongation for the ruptured Achilles tendon. The relative elongation of the ruptured tendon together with overlap of the tendon ends on the cross-sectional area determines the treatment for the patients receiving individualized treatment: 1) patients with 0-6% elongation of the tendon and a minimum of 25% tendon are treated non-operatively 2) patients with 7% elongation or more or less than 25% tendon overlap are treated operatively.

Reflective markers placed on the patients skin with tape on specific anatomical locations, in total 19 markers. The reflective markers are being filmed by 8 infrared cameras hanging on the walls around the laboratory. Thereby, the joint angles during gait will be measured, and, in combination with the ground reaction forces from two force plates embedded in the floor, the joint moments and powers will be calculated.

The examination of both the total and the free part of the achilles tendon of both the injured and un-injured leg is performed. The total length of the tendon is defined under the description of the intervention. The free part of the achilles tendon is defined as the distance between the proximal border of calcaneus and the musculotendinous junction of the soleus muscle and the achilles tendon. The method will be used both diagnostically for the individualized treatment and as a secondary endpoint.