Question

Have there been any studies on the effect of nutrition and exercise programs (e.g., underwater treadmill, hill work, etc.) on horses with "sticky stifles”?

Answer

Also called locking stifles, “sticky stifles” are caused by upward fixation of the patella and occurs when the medial ligament catches over the end of the femur and does not release. Horses can stand for long periods of time without lying down because they can lock the stifle in one leg and relax the other leg so standing requires less muscular effort. A malfunction in the release of this mechanism leads to locked stifles.

The traditional method of treatment for locking stifles is cutting of the medial patella ligament so it is no longer able to catch over the end of the femur. This procedure is no longer recommended. Though long considered useful, the technique often results in complications.  Other veterinary techniques such as splitting the ligament or injection of irritants are now more popular treatments.

Measures to increase muscle strength (particularly of the quadriceps muscles), improved body condition, and corrective shoeing are important strategies before considering veterinary intervention, including surgery, for the more severe cases.

In mild cases, exercise has been recommended to strengthen muscles and resolve the problem. The aim is to improve the muscle tone of the quadriceps and hence tension in the patellar ligaments, to achieve stability, and to reduce the laxity in the medial patella ligament. In younger horses, this may be achieved by simply increasing work that develops the hindquarter musculature, especially the quadriceps. Controlled hill work is one way of doing this.

Corrective shoeing goals include encouraging hoof rotation by trimming the inside wall or applying a lateral heel wedge, and promoting medial breakover by rounding the medial aspect of the toe of the hoof or shoe.

In one study¹ looking at the success rate of various treatments, 40% of horses with locking stifles showed complete recovery, and 20% had marked improvement following corrective shoeing.  Another 10% of affected horses showed improvement when corrective trimming was combined with weight gain and exercise.

There are reports of young affected horses showing no further signs after gaining 55-100 lb (25-50 kg). This is thought to relate to enlargement of the fat pad behind the patella. Therefore, the nutritional goal is to feed calories in excess of daily requirements so the horse gains weight. Care must be taken not to feed in a way that predisposes to hindgut acidosis, colic, or laminitis.

With appropriate changes to hoof care, exercise, and body condition, many cases of stifle lock will resolve, but others require veterinary treatment.  Seek advice from an experienced veterinarian.

¹Upward fixation of the patella in horses: prevalence, results of conservative and surgical treatment
Michèle Dumoulin UGent, Frederik Pille UGent, Paul Desmet, Ann Martens UGent and Frank Gasthuys UGent (2004) Proc. 12th congress of the European Society of Veterinary Orthopaedics and Traumatology (ESVOT). p.230-230