Hock Osteochondrosis

Hock Osteochondrosis (Osteochondritis Dissecans, OCD) is a hereditary developmental condition that uncommonly affects the hock (ankle joint) of medium and large breed dogs, including Labradors and Rottweilers.

One bone of the ankle joint is called the talus. It has two ridges — the medial and lateral trochlear ridges. In osteochondrosis, the bone and cartilage that form one ridge (usually the medial ridge) do not develop properly and fragment / fracture off. This means there is a loose portion of bone and cartilage within the ankle joint, and part of the weight-bearing surface is abnormal, causing joint inflammation, instability, swelling, thickening, arthritis (degenerative joint disease), stiffness and lameness.

It is a developmental disease, with the problem typically occurring between 3 and 6 months of age; however, in some dogs if the problem is mild, it may not be picked up until later in life. Diagnosis has three complementary parts: orthopaedic (physical) examination of the ankle joint, which is highly suggestive but not absolute; X-rays, which are good for diagnosis and for planning ankle replacement or fusion surgery; and CT scan, which is the gold standard, most accurate way to make the diagnosis and is particularly helpful if the lesion is subtle or if considering fragment removal.

Management options range from conservative care to salvage surgery:

• Conservative (non-surgical) management — in many dogs the problem is relatively mild and can be managed conservatively life-long as per an arthritic joint: keeping body condition slim, managing exercise to minimise boisterous and high-impact activity, using anti-inflammatory drugs on an “as necessary” basis, nutraceutical products (e.g. Yumove, Synoquin, Antinol), and hydrotherapy and physiotherapy as needed.
• Fragment removal — can be considered in young 6 to 12 month old dogs, but success is difficult to predict and results can be disappointing; at best, 50% of dogs would see some improvement, but not be cured. This is best planned from a pre-operative CT scan.
• Total Ankle Replacement — a salvage procedure recommended only for dogs struggling and not coping with conservative management. It can be done at any time, but the procedure is very much in its infancy, having only just become commercially available (2020). Size options are limited, so currently only some dogs (typically 35–40kg) can benefit.
• Pantarsal arthrodesis (ankle fusion) — also a salvage procedure for dogs not coping with conservative management; the ankle joint is completely fused so has no movement, but the painful joint is eliminated, therefore functional recovery is excellent with usually near normal hindlimb function achieved.

Many dogs with hock osteochondrosis can be managed successfully with conservative care life-long. Where surgery is needed, outcomes vary by procedure.

Fragment removal has an unpredictable success rate — at best, 50% of dogs would see some improvement, but not a cure. Pantarsal arthrodesis (ankle fusion) provides excellent functional recovery with usually near normal hindlimb function, although the surgical procedure comes with a long list of potential complications, the most severe of which would be surgical site or implant infection, wound breakdown or skin necrosis (death). The published complication rate for arthrodesis is 30%, but we would estimate ours to be much lower at 10% or less.