Equine Medical Service
3021 W. County Rd. 64
Fort Collins, CO 80524
Office
(970) 568-9445
FAX
(970) 568-0705
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Many horses that exhibit hind-end weaknesses and/or lameness may be having pain associated with the hock. The hock is the large joint located between the stifle and fetlock. The hock receives a tremendous amount of the load during motion, providing propulsion along with the stifle. Therefore, this hard working joint is the most common site for rear limb stress, sometimes resulting in pain and performance limiting problems. Additionally, if a horse is reluctant to use his hock, because it's sore, over time other compensating structures, such as the back muscles and stifle can start to experience pain and weakness of their own. As one can see a horse with a hind-end weakness may have multiple problems. It is the veterinarian's job to try and help the horse by providing a diagnosis, which usually takes some considerable time to sort through, hopefully resulting in a plan to improve the horse's performance.
The most common hock disorder is distal tarsal osteoarthritis or "bone spavin". The hock consists of six bones and four joints. The lower (distal) two joints can develop inflammation, with ensuing degeneration of the cartilage and remodeling of the underlying bone. These distal two joints do not contribute much motion as compared to the large proximal (upper) hock joint, but they can be a significant source of pain when inflamed and arthritic.
The three types of spavin:
-Tarsitis- this is when there is only soft tissue inflammation around or in the small joints, not resulting in bony remolding, therefore there isn't any radiographic abnormalities. Tarsitis is mostly seen in young performance horses and can develop into bone spavin.
-Osteoarthritis (bone spavin)- as described above bone spavin is associated with the load the hock receives. The stress of "wear and tear" and/ or repetitive performance trauma due to the demand of some horses careers will start to create degenrative changes of the cartilage and inflammation to the underlying bone. Conformational variations sometimes predispose a horse to development of spavin. In addition some performance events create added stress to the hock, examples include western performance, rodeo, jumping, dressage and pulling events. Shoeing practices, such as trailers, calks, and hoof imbalances can also be a culprit.
-Juvenile spavin- is associated with abnormal development of the small cubical bones in the hock, possibly due to osteochondrosis( OCD), incomplete ossification of these bones in premature or over-term foals, with subsequently crushing of the cuboidal bones. Horses with juvenile spavin are distinguished from other types in that there has not been sufficient work or training to cause bone spavin. Fortunately, juvenile spavin is relatively uncommon.
Bone spavin usually results in chronic, intermittent lameness that worsens with increasing performance demands. Spavin may also be associated with less specific signs such as reduced performance, reluctance to work of the hind end, behavioral/training problems, and back pain. Affected horses will be most lame when they are first put to work, and tend to warm out of it. Diagnosis is based on the history, appearance and conformation of the hock, lameness exam, flexion tests, followed by radiographs. Complicated cases may require local blocks and sometimes more advanced imaging such as nuclear scintigraphy.
Treatment options for bone spavin include medical and surgical: Medical treatment encompasses a long list of options. Intra-articular corticosteroids are commonly used as an effective treatment, providing pain relief (typically a few months to a year). Some mild cases, exhibiting low-grade lameness, various trial medical therapies are initiated. Anti-inflammatory such as "bute" can be used initially for short-term relief. Hyaluronic and Glycosaminoglycans are commonly used for management and prevention. Other adjunctive therapies may include an exercise schedule, acupuncture, chiropractic, shockwave, and magnet. Additionally, shoeing changes are sometimes indicated to achieve balance.
Over time the two lower hock joints may naturally fuse, thus eliminating pain. Natural fusion does not occur with all horses. In some cases where medical therapies do not seem to be helping, surgery may be indicated. Surgical fusion should only be attempted in horses that are not responding to intra articular injection. Hock drilling removes the cartilage and promotes fusion of the joints. Sometime pins or plates are used. Laser fusion is a new technique that is showing some positive results, however studies are still pending. The success rates vary and complications with the procedure and anesthesia weight in on determining surgery candidates. Approximately 50% of horses will show improvement with drilling.
Bone spavin doesn't have to be career ending. Horse owners may be able to minimize the risk of osteoarthritis by treating injuries promptly, and by modifying performance demands in horses with poor conformation. Young horses should be monitored for early signs of hock pain. Every horse's situation is different, working with a veterinarian to achieve the required care and attention can optimize the performance of your horse.
