Don't Be Stopped By A Stifle Injury Part 1

If you know that your horse has been kicked or has hit a fence hard on cross-country, diagnosing a stifle problem shouldn’t be a problem. But stifle injuries may involve soft tissues, the bones, or both—which can sometimes make diagnosis and treatment challenging. Rick Mitchell, DVM, of Fairfield Equine Associates in Newtown, Conn., said that in most athletic horses, hind limb injuries more commonly involve the hock and suspensories rather than the stifle. “But the stifle should always be considered when diagnosing a serious hind limb lameness,” he said. The stifle is a large, complex joint composed of four bones, two menisci (crescent-shaped discs of fibrocartilage attached to the joint surface) and 14 ligaments. It is one of the strongest and most well-supported joints and is actually three separate joints—the medial femoro-tibial joint, the lateral femoro-tibial joint and the femoro-patellar joint. The stifle also has three distinct joint compartments filled with lubricating fluid. Is It The Stifle? One of the classic signs of stifle lameness is a shortened anterior phase of the stride. “The horse may or may not demonstrate a mild toe drag. In severe cases the horse may appear to be on the toe, unwilling to put the heel down—meaning he doesn’t want to extend the leg,” said Mitchell, explaining that the horse is trying to protect the joint by keeping it flexed. “Some horses with more subtle stifle lameness merely have a reduced willingness to bend toward the affected side. They lose suppleness and flexibility on that side. Additionally they may have an irregular or roughened canter, more often when moving away from the affected side,” he added. The horse may demonstrate back and croup soreness, including discomfort and sensitivity while being groomed and saddled. “All of these signs are non-specific for hind limb lameness; none are truly specific for the stifle,” Mitchell said. Without the presence of a known injury like a kick or some other type of blow to the joint, and without the presence of severe swelling/enlargement and sensitivity at the stifle, the only way to be sure the stifle is the site of injury is to eliminate other causes of lameness. When evaluating a lame horse, Mitchell almost always wants to see it work under tack. “This is a big aid. Working under tack may sometimes accentuate lameness, and it can also help us learn a great deal more about the lameness. You don’t need to do this with every hind limb lameness, but it’s a valuable tool. There are a number of horses that you must see working under tack in order to determine level and type of lameness,” he said. Certain flexion tests can guide a vet to the appropriate joint, but the hoof and lower leg must first be eliminated as the source of lameness through nerve blocks. “Then you are centering on the stifle as a likely cause,” said Mitchell. “In a more specific examination you can do joint articular blocks on the stifle itself to determine the source of lameness.” Ultrasound and radiographs can help the veterinarian pinpoint and evaluate the area of injury, but it’s important to first try to narrow it down and localize it, as with nerve blocks. Once the stifle has been determined to be the problem, X-rays may be taken of the joint to rule out cyst formation, fracture, osteochondral fragmentation or chronic arthritis. “If the horse has had problems for a long time, with arthritic changes, this can be determined with an X-ray,” said Mitchell. Soft tissue inflammation or damage, however, won’t show up on radiographs, so this emphasizes the need for careful examination and comparison to the other joint. Blocks within the joint, to eliminate lameness, and then ultrasound as a means of evaluating the joint, can be more helpful than radiographs if it’s a soft tissue injury.