Delayed Release of the Patella
The clinical signs of this condition depend of its severity. It occurs most often in young horses and ponies, especially those which are unfit and poorly muscled. In the most severe cases the leg becomes stuck in extension and the patella is “locked.” The horse may hop on 3 legs, dragging the affected leg behind it. The horse may release itself spontaneously. Some horses remain unable to flex the leg and it may be necessary to force the horse either to back or to jump forward in order to release the patella, which has become stuck on the upper part of the femur. This may happen intermittently several times a day, especially if the horse is kept in. One or both hind legs may be affected.
In less severe cases the patella moves jerkily and its release from the position when the leg is extended is slightly delayed. This may be most obvious when the horse walks up or down a slope or when pushed sideways. If moved over in the box, the horse may move the leg very stiffly. It may find it difficult to make smooth downward transitions from trot to walk and the back legs may appear slightly uncoordinated and jerky.
Treatment of Delayed Release of the Patella
In many horses and ponies the condition appears to be related to poor muscular tone of the quadriceps muscles. If the horse is kept in work and got fitter, the condition frequently improves and with enough time disappears completely. Hill walk is particularly beneficial, as are long, slow canters. Work in straight lines is often preferable to work in circles. Some people feel that elevation of the heels of the hind feet with special wedge-heeled shoes is helpful.
In horses and ponies which fail to respond to conservative treatment, a simple surgical procedure, cutting the medial patellar ligament, usually effects a cure. There are potential complications of this procedure and it should be reserved for those horses for whom regular work has failed to produce adequate improvement.