Lameness is a common malady in young dogs. Numerous differential diagnoses exist for lameness, but when you're looking for
"horses rather than zebras," the list becomes quite short.
The first step in diagnosing any lameness is localization. Observe the animal's gait at a walk and run. Palpate the limbs
in standing (weight-bearing allows for better assessment of joint effusion) and recumbent positions.
This article, the first in a two-part series reviewing lameness in juvenile dogs, reviews common conditions of the forelimb.
See Table 1 for an overview of assessing juvenile dogs exhibiting forelimb lameness. (And see the Related Links below for
Part 2 of the series.)
Table 1 Keys to identifying the cause of lameness in juvenile dogs
Lameness localized to the limb in general could be panosteitis, which affects the long bones of large- and giant-breed dogs
at 5 to 18 months of age. It results in acute lameness and pain on palpation of the long bones. Its cause is largely unknown.
Panosteitis is characterized by endosteal new-bone formation, giving affected long bones the radiographic appearance of an
increased and blotchy density of the medullary canal. The condition can affect multiple bones concurrently or sequentially.
Treatment includes supportive care, analgesics and time. Panosteitis tends to be self-limiting but can recur, although it
is unlikely to do so in the same limb.
Localization to the distal metaphysis of the long bone in large- and giant-breed dogs that are 3 to 5 months old should lead
you to consider hypertrophic osteodystrophy (HOD), an uncommon disease of unknown etiology characterized by marked necrosis,
inflammation and hemorrhage in the metaphysis adjacent to the physis. These changes lead to the radiographic appearance of
a pseudo or double physis seen at the distal aspect of the long bones and are pathognomonic for HOD (Figure 1).
Figure 1: A radiograph of the antebrachium in a young dog with hypertrophic osteodystrophy (HOD). Note the arrows pointing
to the double or pseudo physis of the distal radius and ulna that is pathognomonic for this condition.
Affected dogs exhibit acute onset of swelling over the distal limbs, severe pain, anorexia and fever. The standard treatment
for HOD includes supportive care, nutritional support and analgesics. Peracute and severe cases may benefit from a short course
of corticosteroids. Antibiotics may be used to treat secondary infections (a specific infectious cause for HOD has not been
identified, nor has a specific pathogen been isolated in these cases). Mild cases often spontaneously resolve. HOD is a self-limiting
disease, and recurrence is rare.
Keep in mind that, as with panosteitis, it is unlikely HOD will recur in a single limb. So if recurrent single-limb lameness
is noted in a young dog, further evaluation for other possible causes of the lameness is warranted.