Carpal Laxity in Kittens

What is carpal laxity?

Carpal laxity is a condition in which the carpus (wrist) has an abnormal or excessive range of motion. Normally, when a cat puts weight on its leg, you should be able to draw a nearly straight line vertically through the carpus. However, in a cat with carpal laxity, the wrist is lax (loose) and doesn’t stay in its normal position. This condition is extremely rare in kittens. There are two ways that carpal laxity can show up:

Carpal hyperextension (more common): The carpal (wrist) joint is hyperextended (bends beyond its normal range of motion). Affected kittens appear flat-footed in the front legs, because the wrist collapses towards the ground. The accessory carpal pad (the small pad located behind the carpus) may even touch the ground when these kittens walk.

Carpal flexion (less common): The carpal joint is not sufficiently extended. The wrist bends forward when the kitten puts weight on it, causing the wrist to bulge outward from the front of the leg.

What causes carpal laxity?

The underlying cause of carpal laxity has not been conclusively determined, but many theories have been proposed. One theory suggests that the condition may occur when bones grow faster than tendons. Potential causes include nutrition (specifically excessive caloric intake and/or excessive calcium intake), genetic factors, and being raised on slippery flooring.

While a single underlying cause of carpal laxity has not been identified, most cases involve some degree of muscle weakness. A lack of exercise and increased time on slippery surfaces may play a role, either individually or in combination with other factors. Without adequate development of the muscles that surround and stabilize the carpus, the joint itself becomes unstable.

Although carpal laxity typically affects both front legs, sometimes a single limb is affected. This most commonly occurs when the other limb is splinted or bandaged due to an injury. When a kitten’s leg is splinted, the opposite leg must bear all the weight. Many kittens do not have adequate muscles around the carpus to effectively bear the kitten’s full weight, so the carpus may become unstable.

What are the clinical signs of carpal laxity?

Signs of carpal laxity may be seen at any time from 6 weeks of age onward, but the condition is usually noted between three and six months of age. Some kittens develop signs seemingly overnight, while other cases progress slowly, over a period of several days to weeks.

In most kittens, the condition does not appear to be painful; in mild cases, affected kittens often run and play normally. These kittens do not seem to notice they have an orthopedic issue until the owner notices the front legs look unusual (carpal flexion or carpal hyperextension). In more severe cases, affected kittens may appear weak on the affected limbs and reluctant to walk or run.

How is carpal laxity diagnosed?

Your veterinarian will begin by performing a thorough physical exam and examining your kitten’s carpi (wrists). They will also evaluate your kitten’s overall body condition, check other bones and joints for abnormalities, and look for signs of pain when palpating (feeling) the abnormal joints, because pain could suggest an injury or other abnormality.

Radiographs (X-rays) may also be performed, especially if only one leg is affected. Radiographs often appear normal in kittens with carpal laxity, but they can be used to rule out other conditions (like a broken bone) that might also cause a joint abnormality.

Your veterinarian may also recommend bloodwork. Blood tests are used to look for medical causes of muscle weakness, and include a complete blood cell count and serum biochemistry panel. Additionally, blood tests can help evaluate the overall nutritional status of your kitten.

How is carpal laxity treated?

Affected kittens should be kept on surfaces that provide a secure, non-slippery footing. Carpet, grass, and rubber mats are all good flooring options for kittens with carpal laxity. These surfaces minimize the risk of injury and allow the muscles around the carpus to develop to help stabilize the joint. In severe cases, your veterinarian may place a light bandage or wrap around the carpus for added stability. This bandage is left in place for approximately one week. Sometimes a splint will also be used; studies show that splint or no splint can be effective.

Your veterinarian may also make dietary recommendations for your kitten, especially if your kitten has been receiving less-than-ideal nutrition. While the role of nutrition in carpal laxity is unknown, the safest option is to feed a high-quality, well-balanced commercial kitten food.

Your veterinarian may also recommend physical therapy exercises you can do at home, depending on your kitten’s condition. Massage and passive range of motion exercises (flexing and extending the carpus) can both help address carpal laxity.

What is the prognosis for carpal laxity?

In most cases, carpal laxity is self-limiting (resolves without treatment). Most kittens with carpal laxity appear completely normal within six to eight weeks.