The hock is one of the most important joints in a horse’s body. Located in the hind leg, it sits between the stifle (equivalent to the human knee) and the fetlock (equivalent to the ankle). In terms of biomechanics, the hock joint does an enormous amount of work — it is the primary source of propulsion in most gaits, absorbing and releasing energy with every stride. Understanding hock horse anatomy is essential for anyone serious about equine health and performance.
Anatomy of the Hock
The hock is not a single joint but a complex of four joints stacked vertically. The uppermost and most mobile is the tibiotarsal joint, which accounts for the vast majority of flexion and extension. Below it sit three lower joints — the proximal intertarsal, distal intertarsal, and tarsometatarsal joints — which have very limited independent movement but play an important role in load distribution.
The bony structure includes the tibia above, the cannon bone (third metatarsal) below, and a cluster of tarsal bones in between — the talus, calcaneus, central tarsal, and the first through fourth tarsals. The calcaneus projects backwards to form the point of hock, the bony prominence visible on the back of the leg. Surrounding this structure are major tendons and ligaments including the long and short plantar ligaments, the cunean tendon, and the digital flexor tendons, which run through the tarsal sheath.
How the Hock Generates Power
When a horse moves, the hock flexes on landing to absorb impact, then extends powerfully to push off and propel the horse forward. In collected work, the hindquarters carry more weight and the hocks flex more deeply under the horse’s body — this is why collection demands so much from these joints. In lateral movements such as half-pass and shoulder-in, the hocks must flex, extend, and rotate simultaneously, which is why these exercises reveal weaknesses early.
Working horses — particularly those in jumping, dressage, and eventing — subject their hocks to significant cumulative stress. Regular veterinary assessment and proactive management are standard practice at competition level for this reason.
Common Hock Problems
The hock is one of the most common sites for lameness in performance horses. Key conditions include:
- Bone spavin — osteoarthritis of the lower hock joints, and one of the most prevalent causes of hind limb lameness in working horses. Horses often show stiffness when first brought out of the stable, which improves with warm-up. Diagnosis is confirmed via X-ray; management typically involves joint injections, corrective shoeing, and sometimes surgical fusion of the affected joints.
- Bog spavin — a distension of the tibiotarsal joint capsule, appearing as a soft, fluid-filled swelling on the inner aspect of the hock. Often a response to trauma, poor conformation, or excessive workload in young horses. In many cases it causes no lameness and is cosmetic only.
- Thoroughpin — fluid accumulation in the tarsal sheath surrounding the deep digital flexor tendon, presenting as a bulge above and to either side of the point of hock. Usually benign but worth monitoring.
- Capped hock — a bursitis of the calcaneal bursa at the point of hock, typically caused by repeated trauma from kicking stable walls, falling in a trailer, or lying on hard ground. Produces a distinct, often firm swelling at the point of hock.
- Hock strains and soft tissue injuries — damage to the ligaments or tendons of the hock, often associated with slips, overexertion, or poor footing.
Assessing and Treating Hock Issues
A flexion test is a standard tool for identifying hock problems. The vet holds the hind leg in full flexion for 60–90 seconds, then releases it and asks the horse to trot immediately. Increased stiffness or lameness following the test points to hock involvement. X-rays assess bony changes; ultrasound examines soft tissue. The British Equine Veterinary Association (BEVA) provides guidance on lameness workups at beva.org.uk.
For joint-related conditions, intra-articular corticosteroid injections remain the most common first-line treatment. Hyaluronic acid and newer biologic therapies such as IRAP and PRP are increasingly used alongside steroids. Corrective farriery — wedge pads or rolled toes — can reduce the biomechanical load on specific joints. For horses with advanced lower hock arthritis, chemical or surgical fusion of the distal joints can eliminate pain whilst preserving overall function; many horses return to full work following this procedure.
Frequently Asked Questions
What does hock arthritis look like in a horse?
A horse with hock arthritis often shows hind limb stiffness, particularly at the start of exercise, which typically improves as the horse warms up. You might notice a shortened stride behind, reluctance to engage the hindquarters, or a subtle dragging quality to the movement. In some cases there is visible swelling around the joint. A positive response to a flexion test, combined with X-ray evidence of joint narrowing or bone remodelling, confirms the diagnosis. Early-stage bone spavin may cause intermittent, mild lameness that owners initially overlook.
How often should hocks be injected?
This varies considerably depending on the horse, the condition being managed, and the response to treatment. Many horses in regular work receive hock injections once or twice a year as a maintenance measure. Your vet is best placed to recommend a protocol based on clinical examination, imaging, and the horse’s workload. Over-injection is a genuine concern — the goal is effective management with the minimum necessary intervention, not treatment on an automatic calendar cycle.
Can a horse work with a capped hock?
In most cases, yes. A capped hock is a cosmetic blemish resulting from bursal distension and does not typically cause lameness. Horses can usually continue normal work, though the original cause of trauma should be addressed — padding stable walls, improving bedding depth, and ensuring good trailer footing. If the swelling is hot, painful, or accompanied by lameness, veterinary assessment is warranted to rule out a problem beyond simple bursitis.