Stifle Lameness in Performance Equine Athletes

Josh Zacharias, DVM, MS, DACVS 

Lameness is the leading cause of poor performance in the rodeo athlete, whether you’re riding a barrel horse, rope horse, or steer wrestling horse. Lameness is the inability of a leg to be moved in a normal manner, which is usually in response to pain. The severity of lameness can range from non-weight bearing to a subtle, almost non-visual gait alteration that may only be felt by a rider or as a decrease in performance. The shear strength and speed of a horse and the abrupt stops and turns that are performed lead to many stresses on the joints, tendons and ligaments of the hindlimbs. Although a one-time event or injury can cause lameness, it is more common for these repetitive events to lead to joint inflammation and subsequent pain.

The stifle is the largest and most complex joint in the horse, which is commonly overlooked as a primary source of lameness. A typical problem in a barrel horse might be going wide on a barrel. In a calf horse, it may be reluctance to get in the ground or setting the hindquarters off to one side when stopping. These are usually signs of a hindlimb lameness, which in most cases can be attributed to either the hock or stifle. A large number of horses on the circuit today have had their hocks injected at some time to treat distal hock pain. However, quite often the pain may primarily come from the stifle instead of the hock. Horses with stifle lameness may also drag their toes and have a shortened stride.

A thorough lameness evaluation is required to identify the source of pain. Distinguishing between hock and stifle pain can be difficult because both joints may be affected. In most horses that are sore in both areas, the scenario of pain originating from the stifle leading to compensatory pain in the hock (and potentially the back or sacroiliac joint) is more common than the reverse. Flexion and stress tests are helpful in finding the culprit of the pain, but the results are often not completely definitive between the hock and stifle. Diagnostic analgesia is used to localize the pain prior to imaging of the affected area. Radiographs are taken to identify signs of joint disease or traumatic injury. Ultrasound is performed to examine soft tissue structures that may be injured such as the collateral or cruciate ligaments and the meniscus.

A large portion of horses that have pain originating in the stifle joint due to arthritis respond to intra-articular medication. This therapy usually includes a steroid anti-inflammatory drug as well as hyaluronic acid (HA) which is a normal component to cartilage and synovial fluid. IRAP is another product often injected into the joint that can give a longer duration of action, especially in horses that become refractory to steroid injections. It is important to remember that conventional therapies should not be excluded from consideration such as non-steroidal anti-inflammatory drugs, proper shoeing, joint supplements, rest, and rehabilitation.

In lameness cases that fail to respond to treatment or have been localized to the stifle but imaging is unremarkable, visual examination of the joint via arthroscopic surgery often yields impressive findings. These include cartilage damage and meniscal or ligamentous injuries. Many conditions can be treated and a more specific prognosis can be made with arthroscopic surgery.

If your horse is not performing well in the arena, consider a lameness exam to identify the source. Treatment of the proper area will get your horse back to full potential quicker. Specific joint therapies will be discussed in further detail in a following article.