Bone spavin is the common name for osteoarthritis of the lower joints of the hock. It is the most common cause of lameness in the hock and is usually seen in older horses although can occur in young horses, especially if they have poor conformation or other predisposing factors.
Causes of bone spavin include uneven loading of the joint which may be exacerbated by poor conformation, especially ‘cow hocks’ or ‘sickle hocks. Poor trimming or shoeing can also be a contributing factor.
Horses that are used for athletic purposes, especially jumping, may also develop bone spavin due to repeated concussive force on the hock joints. Over time the cartilage within the joint becomes compressed causing inflammation of the joint and bone remodelling. Affected horses usually show a gradual onset lameness affecting one, or both, hindlimbs and often exacerbated by flexion. This may be first noticed as a reluctance to work, especially if jumping. There may also be dragging of the toe, causing increased wear of the hoof or shoes. Diagnosis of bone spavin is usually made after performing a joint block, which involves injecting local anaesthetic into the tarsometatarsal joint. If this results in a significant improvement in lameness then xrays are taken. Bone scanning or MRI can also be useful, particularly in horses that are difficult with needles or dangerous to block, or if xrays are inconclusive.
There are a number of approaches to treating bone spavin, all of which are aimed at reducing inflammation, making the horse more comfortable and promoting fusion of the joints. In cases of foot imbalance corrective shoeing is important. Pain relief is often given in the form of bute and we will usually advise ongoing use of a joint supplement. Steroids can be injected into the affected joint(s) to reduce inflammation. It is possible to inject other, irritant, substances into the joint to promote fusion but this is not usually performed as a first line treatment. Bisphosphonate drugs can also be given to prevent excessive bone remodelling, reduce pain and promote fusion. Once the affected joint has fused, a process which may take six months to two years, it is usually non-painful and lameness resolves.
Please call the practice if you have any further questions.