Carpal Hyperextension in Cats

Carpal hyperextension in cats is a condition in which the carpus, or wrist, in one of your cat’s limbs becomes over, or hyper, extended. When this extreme flexion occurs, the supporting ligaments in the carpus can become strained or torn, causing injury. When the ligament is weakened the joint is no longer able to maintain proper position, causing a lack of ability to support weight on the affected limb.

Signs of carpal hyperextension in your cat will include lameness and an inability or unwillingness to bear weight on the affected limb. The full list of symptoms to watch for includes:

• Limping or inability to bear weight on limb
• Unwillingness to jump or climb
• Swelling of carpal joint
• Characteristic heel touching ground stance

Carpal hyperextension in cats is typically the result of an injury to the affected joint. The injury may be sudden and the result of a trauma such as a car accident or other major impact or after landing from a jump from an extended height, or it may be due to repetitive use of the joint causing minor ligament damage over time that has a cumulative effect. Cats with diabetes may be more prone to carpal hyperextension. This is due to the disease’s effects on many bodily tissues, including weakening of ligaments.

Diagnosis of carpal hyperextension in your cat will begin with a thorough physical exam by your veterinarian. You should provide your vet with a complete medical and symptomatic history of your cat. If the injury has been recurring or has improved and regressed over time, this may help your vet rule out other structures in the limb causing the injury.

Your veterinarian will closely observe your cat’s stance and the way they are holding the injured leg. The classic characteristic stance for a cat with a carpal hyperextension injury involves the wrist being fully extended and touching the ground in an unnatural 45 degree position. To the pet owner, this can appear as if your cat’s wrist has collapsed and they are now walking on their lower leg instead of their paw.

The definitive test for carpal hyperextension includes specialized x-rays known as stress radiographs. In this procedure, stress is applied to the joint at multiple locations in order to help identify which portion of the ligament and which specific wrist joint has become injured. In order to provide the best images, your cat will need to remain calm and still for the x-ray. Some cats will need to be given a mild sedative or anesthesia in order to obtain clear and accurate images.

Unlike many other tissues in your cat’s body, ligaments are unlikely to heal or regrow. In mild cases of carpal hyperextension, your vet may recommend a wait-and-see approach to allow time for scar tissue to form in the damaged ligament. The scar tissue will sometimes act as a stabilizer for the damaged ligament. Additionally, these types of injuries typically occur as a result of a large amount of jumping or other movements that put a significant amount of pressure on the carpal joint of your cat. In order to have any chance of healing or scar tissue stabilization, your cat’s activity will need to be severely limited.

Given the difficulty in a conservative approach, the preferred method of treatment of carpal hyperextension is surgery to fuse the affected joint. Fusing the joint removes the ability of the carpus to flex and bend, creating a stability that is missing once the ligaments have become damaged. For this surgery, your cat will need to undergo anesthesia. Before being put under anesthesia your veterinarian will run a full blood panel to confirm there are no underlying medical conditions that may make the surgery more risky. While there are a few common complications, such as infection or failure of the bones to fuse properly, overall surgery to fuse a joint affected by carpal hyperextension is an effective treatment option.

For cats that undergo successful surgery for fusing an affected joint, their prognosis is good. You will need to carefully follow your veterinarian’s postoperative instructions, including keeping your cat in a calm, quiet place where their motion is limited while they heal from surgery. You will also need to administer all prescribed medicines to avoid any postoperative infections.

Long term, fusion of the joint will have some minor impact on your cat’s mobility. Due to lack of flexion, your cat may be unable to jump as high or as far as it used to. Cats that have had this surgery should be kept indoors and not exposed to outdoors obstacles and dangers.

With proper post-operative care and long term follow up and care, your cat will have a good quality of life after a carpal hyperextension injury and should make a good recovery.