Horse Hock Joint Anatomy

The hock, or gambrel, is the joint between the tarsal bones of a quadruped (long-legged) mammal. This joint is a high-motion joint that allows for flexion and extension of the hindlimb, as seen in other tetrapods, such as humans.

The joints in the limb must be flexible to absorb the tremendous forces put on the lower leg of a working animal. The hock also helps to prevent excessive movement of the hip and back joints.

A healthy hock should look stout and heavy with no obvious swellings. The left and right hocks should look symmetrical.

Rapid flexion and extension of the hock generate friction between closely adjacent structures, especially tendons and the underlying bone. This requires the formation of bursae, which cushion and reduce friction. The compact structure of the hock means that a number of tendons are squeezed into a small space and many of these are interwound or interlaced with each other. This may increase the risk of irritation and injury.

Normally the point of the hock is of uniform height when viewed from either side or from behind, and when the horse is standing on a hard surface. This symmetry is essential for proper function of the joint because it allows the gastrocnemius tendon to be pulled against the tibia at the point of the hock, initiating flexion of the knee and lowering of the back of the leg.

When the hock is not properly functioning, there are often noticeable abnormalities in gait. The most common problem is disruption of the gastrocnemius tendon origin, musculotendonous junction or tendon itself. The result is a dramatic lowering of the point of the hock in standing and when the horse is moving. The joint then becomes less functional and is not able to support the weight of the limb.

This can be caused by trauma, excessive exercise and even conformation problems. The hock acts in unison with the stifle and hip, so if there is an issue in one of these joints it can have a significant impact on the other joints. For example, a horse with OCD in the stifle might start to rotate at the hip joint to protect the hock.

The hock is susceptible to osteoarthritis, which is commonly found in performance horses and can be a consequence of exercise or ageing. This condition can lead to bony proliferation, narrowing of the joint space and cartilage damage. Eventually, the joint can become completely fused, which inhibits movement and results in lameness.

It is important that horse owners know what a normal hock should look like so they can recognize any abnormalities. Regular examinations with a veterinarian, including radiographic evaluation, are recommended to ensure that the hock is functioning properly. This will allow for early detection of problems that can be corrected before the damage becomes more severe. This is especially important in performance horses that are exposed to a high level of activity. Regular conditioning of these horses can help to minimize stress on the hock.