Delayed Release of the Patella condition 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.
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.
The lateral trochlear ridge of the femur is one of the most common sites for osteochondrosis. This condition is usually seen in young horses (6 months to 3 years old) but is occasionally identified in older horses. There is marked distension of the femoropatellar stifle joint capsule and slight to moderate lameness characterized by a stiff limb flight, lowered arc of flight of the foot with or without an intermittent roe-drag. Lameness may be aggravated by flexion of the limb. The condition may affect one or both limbs. Young horses with both stifles affected may become slightly roach-backed and have difficulties in getting up after laying down. Diagnosis is confirmed by radiographic examination. Without treatment lameness usually persists. Provided that the lesions are not too severe, surgery is generally successful.
The stifle joint is a common location for subchondral bone cysts, which almost always occur at the point of maximum weight bearing in the lower end of the inside of the femur, the medial femoral condyle. They occur most often in young horses when first starting serious work, but are also found in older horses. The horse shows a sudden onset of a variable degree of lameness. The lameness may be extremely subtle or very severe. The horse usually improves with box rest but the lameness recurs when work is resumed. There is only slight distension of the stifle capsule, if any. Prolonged rest (6 to 9 months) results in soundness in approximately 60% of horses. In horses which fail to respond to rest surgery can be performed with a fair prognosis. Evidence of partial subchondral bone cyst filling and cartilage repair has been reported in many cases along with increased comfort and accelerated return to performance after using Vet-Stem Cell™Therapy.
There is a sudden onset of lameness associated with some swelling of the stifle joint capsule. Diagnosis is based on the clinical signs. Rest usually resolves the lameness. The duration of rest depends on the severity of the initial injury. If lameness persists, the stifle should be radiographed.
Bruising of the stifle region is a common injury either as a result of a kick or hitting a fixed fence when jumping. The latter is a common injury of event horses. There is a variable degree of swelling and lameness.
Anti-inflammatory analgesic drugs are extremely helpful in reducing swelling and removing pain. Plenty of slow exercise prevents the horse from becoming excessively stiff, so if it can be turned out in a small paddock or walked in hand regularly, this is helpful. Provided that there is no underlying bony damage the prognosis is good. If the horse does not improve rapidly the stifle should be examined radiographically. A fracture of the patella or other bony damage might otherwise be missed.