However, if a kitten injures the delicate growth plates from which bone grows, this can result in an angular limb deformity (ALD). A cat with ALD has twisted, bowed or rotated bones when compared to the opposite limb. Both the forelimb and hind limb have paired bones (radius and ulna, tibia and fibula, respectively) that should grow at the same rate.
If one bone is damaged and bone growth slows, this “tethers” the partner bone, which responds by bowing or twisting. It’s like tensioning a bowstring — the bow bends, causing in cats a mechanical lameness and altering the smooth articulation of the nearest joints, resulting in pain and early arthritis.
The cat may limp or seem painfully affected by that limb. When you compare 1 limb with its mirror image, the 2 legs are no longer identical.
In the early stages, it may be difficult to spot asymmetry — if in doubt, photograph both legs, and again in 1 month’s time. This helps identify a problem as early as possible. Surgical correction is more successful if undertaken before marked bone bowing occurs.
Kittens’ bone growth mostly takes place at 2–6 months of age. The bones grow in length from soft cartilage growth plates at either end of the long bones.
Injury to the leg, such as being stepped on or trapped in a door, may mean a damaged bone plate, causing scar tissue that prematurely prevents further bone growth. This then hobbles the adjacent bone, which continues to grow, but twists, bows or rotates in response to the restriction.
Because ALD in cats normally results from trauma rather than breeding, usually only 1 leg is affected. If your cat’s front (or back) legs are not a mirror image of each other, she may have ALD.
Radiographs comparing both limbs can confirm ALD, but the gold standard is a CT scan. A far more detailed image, this allows a specialist to assess exactly where the damage is. This allows for accurate surgical planning of the corrections needed to allow the bone to grow straight again.
Specialist orthopedic surgeons assess how best to correct the problem.
The options for surgery include:
- Cutting the too-short bone so it stops holding back the longer bone, allowing it to spring back into a proper shape
- Correct abnormal rotation of a bone, but cutting and realigning it without the twist; the bone is then held in the position with bone plates
- If both growth plates closed too early, an external fixator device may be fitted that has adjustable sliders to allow the bones to be “stretched” a little every day
Kittens will be kittens and dash about, getting under your feet, so accidents do happen. If the kitten has an accident and is lame, get her checked for fractures.
If she recovers quickly, it may be wise to take photographs, and again a couple of weeks later for comparison. While this won’t stop any damage to growth plates, if you spot it early, the chances of a successful corrective surgery are much greater.
- Feline Orthopedics. Scott & McLaughlin. Publisher: CRC Press.
This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Oct. 1, 2015.