Tendon of common digital extensor muscle

On thoracic limb of horses, the common digital extensor tendon (dorsal digital extensor tendon) is the continuation of the common digital extensor muscle. The tendon passes over the dorsolateral aspect of the carpus, continuing distally over the dorsal metacarpus and joined by the branches 

of the interosseous muscle (suspensory ligament) before its insertion on the extensor process of the distal phalanx.

A minor branch  of the common digital extensor tendon inserts on the middle phalanx and some fibres insert on the hoof cartilages.

• Origin: Common digital extensor muscle on the lateral humeral epicondyle
• Insertion: Extensor process of distal phalanx
• Action: Extends carpus and digit
• The common digital extensor tendon is surrounded by the extensor retinaculum and a protective synovial sheath. The tendon sheath begins approximately 10cm proximal to the carpus, extending distally to the level of the metacarpus.

sources : wikivet (https://en.wikivet.net/Tendons_-_Horse_Anatomy)