What Is Hock Swelling In Horses?

Dr Luke Poore graduated from Cambridge University in 2000. He completed an internship in private practice and a surgical residency at Edinburgh University in Scotland. He has worked as a surgeon and orthopaedic clinician in private practices and universities since. Luke started work at the Onderstepoort Veterinary Academic Hospital in 2015 where he is a general equine and wildlife surgeon. His main clinical interests include lameness in the sport horse and racehorse, as well as emergency surgical cases.

- Dr Luke Poore

The hock, situated between the foot and the stifle in the horse, is one of the most complex joints in the equine skeleton. To understand swellings of the hock, it is necessary to know the anatomy of the hock region. The horse’s hock is composed of six bones, four joints and multiple tendons and ligaments. The largest joint at the top of the hock is known as the tibiotarsal joint with the other three smaller joints, the proximal intertarsal, distal intertarsal and tarsometatarsal joints, situated below this joint. It is damage to the capsules of these joints and the bursa or sheaths associated with the tendon and ligaments in this region that causes swellings of the hock region.

Hock movement

The majority of the movement in the hock occurs in the tibiotarsal joint with movement of the other joints limited by the ligaments that surround them and their robust joint capsules. The main movement of the hock is by flexion and extension, although rotational and sliding movements do occur in the lower smaller hock joints.

Competition horses require a full range of extension and flexion of the hock to achieve sufficient hindlimb movement. The hock is particularly important in dressage horses and showjumpers where the degree of collection and hindlimb impulsion is required to be at its greatest. Very significant forces are exerted through the bones, ligaments and joint capsules that comprise the hock in these horses. It is therefore not surprising that the hock is the most common site of hindlimb lameness in the competition horse.

There are several specific conditions that can cause swelling of the hock region.

Bog spavin