By Lisa Gift Krauter, DVM, DACVS, Pilchuck Veterinary Hospital
During the busy summer and early fall months, our horses are often required to perform at their maximum level, and, as such, a number of them develop lameness issues.
Any discussion of lameness in the horse has to begin with the front hoof region. Because the horse carries at least 20% more of his weight on his forelimbs than hind limbs, the front foot region is a common area to develop injuries. The front foot is a complex structure made up of bones and soft tissues (tendons and ligaments), in addition to blood vessels and nerves. The navicular bone and its associated structures, along with the deep digital flexor tendon, provide stability to the back of the foot, while the collateral ligaments of the coffin joint provide stability to the front part. All these structures are prone to injury in athletic horses because of the compressive, pulling and torque forces placed upon them. Diagnosis of these injuries can be challenging because radiographs reveal some bone injuries, but not all. The soft tissues cannot be evaluated with radiographs and, because most of them are located within the hoof capsule, are only partially visible with ultrasound evaluation. With the advent of MRI technology, it is now possible to diagnose injuries to the bones and tendons/ligaments of the front foot to allow for appropriate treatment and thus a better chance of the horse returning to competition.
In both the front and hind limb, injury to the suspensory ligament is a common source of lameness for all types of equine athletes. The suspensory ligament functions to prevent excessive extension of the fetlock joint and thus undergoes extraordinary pulling forces. The lameness associated with the suspensory ligament may initially be mild, and the horse may “wear out of the lameness” with continued light exercise. With suspensory injuries in the rear limb, the rider often initially just feels that the horse has a reduced amount of push. With continued stress, however, these mild strains can progress to ligament tears resulting in a definitive lameness. Because there is often no swelling of the leg, injuries to the suspensory ligaments are usually diagnosed by ultrasound examination following localization of the lameness by local anesthesia (nerve blocks). Treatment often involves some form of regenerative therapy such as platelet-rich plasma or stem cell treatments, shockwave therapy, and a rest/rehabilitation program.
The hock and stifles are common sources of lameness in the rear limbs of equine athletes. The hock is prone to developing bone/joint pain associated with the bottom two of the four joints that make up the hock. Radiographs of these joints often reveal some degree of arthritic change, and treatment often involves the use of intramuscular Adequan or Pentosan injection or injections of anti-inflammatory agents into the affected joints. Pain associated with the stifle can involve either the bones, meniscus separating the bones, or internal ligaments. Diagnosis of which structures are affected may require arthroscopic surgery in addition to radiographs and ultrasonography due to the limited visibility of some of the structures. Treatment may involve the use of intra-articular medications, or in the case of traumatic injury, arthroscopic surgery and regenerative therapy followed by a rest and rehabilitation program.