Page 326 - Canine Lameness

298 18 Tarsal Region

18.6 Osteochondrosis Dissecans

Osteochondrosis/osteochondritis dissecans (OCD) of the tarsal joint is an uncommon disease of
young, mostly large-breed dogs that affects the talus. Either talar ridge can be affected, although
OCD is most common on the medial side. It is not unusual for both tarsi to be affected, so both tarsi
should be carefully assessed for pathology.
OCD fragments can damage adjacent cartilage surfaces, especially if they displace or break into
smaller pieces. If they migrate or are removed, the resultant defect causes joint incongruity.
Because of this, talar OCD reliably leads to OA of the tarsocrural joint. The osteochondrosis frag-
ments can contain a substantial amount of subchondral bone. Unsurprisingly, as fragment size
TARSAL REGION increases, prognosis for good limb use decreases. Reattachment of fragments can be difficult, and
healing is unpredictable. Surgical removal of talar ridge OCD remains controversial. Fragment
removal brings about clinical improvement in about half of treated dogs, but some degree of lame-
ness persists in most and OA progresses regardless of treatment (Van Der Peijl et al. 2012). Dogs
with significant lameness due to OA later in life may benefit from pantarsal arthrodesis. Migration
of osteochondrosis fragments into the synovial sheath surrounding the DDF tendon is a rare con-
sequence of OCD (Section 18.7.4).

18.6.1 Signalment and History
Talar ridge OCD is generally a disease of young large-breed dogs and particularly of Labrador
Retrievers. Other predisposed breeds include Rottweilers, Pit Bulls, and Australian Cattle Dogs.
The majority of affected dogs are female.
Lameness develops during the first year of life and can be seen as early as 4½ months of age. However,
some dogs are presented for evaluation later in life, when tarsal OA begins to affect quality of life.

18.6.2 Physical Exam
Talar OCD typically produces a weight-bearing lameness that is evident at both the walk and the trot.
A shorter stride is taken on the affected limb, and range of motion in the tarsus during each step is
reduced. The limb may be held abducted, especially when the dog rises from a sitting position. These
dogs may also display a positive “sit-test,” making talar OCD a differential diagnosis for cranial cruci-
ate ligament disease (Video 18.3). In the author’s experience, tarsal hyperextension may be present,
but in a recent study this was not found to be a common feature (Van Der Peijl et al. 2012).

Video 18.3

Typical gait with tarsal OCD.

Effusion is usually present on the cranial as well as on the plantaro-medial or plantaro-lateral
aspect of the tarsocrural joint, depending on the location of the osteochondral fragment. The degree
of swelling that is present gives an indication of the size of the fragment; larger fragments (and thus
poorer prognoses) tend to be associated with more impressive effusions. Crepitus may be felt on joint
manipulation, and the dog usually objects to joint flexion and full extension. Occasionally a displaced