This case involves a ten year old hunter mare who presented with a sudden onset forelimb lameness whilst in light work and having had no history of any traumatic episodes. The most salient feature of the clinical examination was distension of the digital tendon sheath or windgall formation and absence of any foot pain. After a thorough aseptic preparation, we blocked the tendon sheath with local anaesthetic; this procedure abolished the lameness. The following day, once all the local had dispersed, we carried out an ultrasound examination of the soft tissue components within the tendon sheath. We also radiographed the fetlock joint to rule out any fractures to the sesamoid bones. Both types of imaging failed to reveal any significant damage to explain the lameness. We therefore decided to medicate the tendon sheath with short-acting cortisone in case the problem was just a synovitis or inflammatory response to trauma. This had the effect of completely reducing the windgall and the mare was rendered free from lameness. She was therefore put back into light walking exercise. Unfortunately the tendon sheath effusion and the lameness soon returned indicating that there had to be an injury which we had not yet identified. The next step with cases displaying this type of history, is to perform an arthroscopic examination of the tendon sheath under general anaesthesia. We took the mare to surgery and we found the problem; there was a substantial split in the medial border of the superficial digital flexor tendon within the annular ligament with a small flap of tissue hinged off the tear. In addition, there was tearing of the medial border of the deep digital flexor tendon. The torn flap of tendon was excised and the remaining strands of tissue were removed using a motorised ressector.

Debridement of the tear in the superficial flexor tendon .

So the free fibres of damaged of tendon were leading to a synovitis or inflammation of the tendon sheath resulting in lameness. Debriding or trimming of all this tendon tissue will allow the inflammation to settle and for the tendon to heal. We will review the comfort level of the horse six weeks post surgery and re-medicate the sheath now that the instigating cause has been removed. All being well, the mare will resume walking exercise at 8 to 10 weeks post surgery. She will stay in a controlled walking regime for 6 to 8 weeks prior to paddock rest for a further 6 to 8 months. The cause of the injury remains a mystery, but must have resulted from some paddock craziness!!