The hip is a simple ball and socket joint with a wide range of movement in all directions, and its efficient function is essential to normal hind-limb movement. The joint consists of two parts: the acetabulum, a cup-shaped depression in the pelvis that forms the “socket,” and the femoral head of the femur (thigh bone), which forms the “ball.”
The stability of the hip joint depends on many factors, including:
- The short ligament that attaches the femoral head (ball) to the deepest point of the acetabulum (socket)
- The joint capsule
- The strength of the muscles that surround the hip
What is hip dislocation?
When the hip dislocates (also known as hip luxation), the femoral head is displaced from the acetabulum (out of socket); in most cases, the femoral head is positioned above and in front of the acetabulum. The most common cause of hip dislocation is blunt force trauma, such as a fall or an automobile injury, but any traumatic injury to the hip area may cause a hip to dislocate.
An increasing number of cats, especially purebred cats (Maine coon, Himalayan, Persian, Devon Rex, and Siamese), are being diagnosed with hip dysplasia (poor hip joint conformation) like that seen in dogs. Hip dysplasia may predispose a cat to hip dislocation.
What are the clinical signs of a dislocated hip?
Most cats with a hip dislocation will have severe hind limb lameness and may not be able to put any weight on the affected limb. The affected limb is often carried in a flexed position (folded or pulled up) and may appear shorter than the other limb. If your cat has had a traumatic injury (e.g., hit by a car), they may have been missing for a few days because they have had difficulty walking home and they may have other, more serious injuries.
Some cats with hip dislocation will naturally create a pseudo joint and may be first diagnosed with hip dislocation when they are X-rayed for another reason. As long as they are pain free and have normal mobility, they may not need intervention.
How is a hip dislocation diagnosed?
Your veterinarian will physically examine your cat and notice that the hip joint is painful when moved. Your veterinarian may also feel a grinding sensation (crepitus) when the femur is moved. Because this condition is painful, your cat may not allow manipulation, and sedation may be required for a full examination.
The diagnosis is confirmed by an X-ray (radiograph). A diagnostic X-ray will show the direction of dislocation and whether there is a fracture in any part of the hip joint. If there is a fracture, it may be more difficult to repair the dislocation. If your cat has other, more serious or life-threatening injuries, these injuries will be treated before your veterinarian addresses the dislocated hip.
What is the best treatment for a dislocated hip?
In most cases of hip dislocation, it is best to replace the femoral head in the acetabulum. The only exception to this rule is if your cat has another illness or if other factors make anesthesia too risky. If the hip is left dislocated, a false joint will form and the cat will have permanent lameness and potentially chronic pain.
Non-surgical treatment: In many cases, it is possible for your veterinarian to push the femoral head back into the acetabulum while your cat is under general anesthesia. This procedure is called closed reduction. The success of a closed reduction increases if the dislocation is recent (i.e., the injury is less than 72 hours old).
After the dislocation is reduced or replaced, your veterinarian may apply a supportive wrap or bandage called an Ehmer sling to immobilize the leg and prevent the hip from popping back out (re-dislocating). This bandage or support wrap will remain in place for 4 to 14 days. Occasionally, a cat may not tolerate this bandage well. In this case, your cat must be closely supervised and their activity must be severely restricted. It is important to ensure that the bandage or support wrap is not too tight and does not distress the cat.
Surgical treatment: In some cases of hip dislocation, it is impossible to place the femoral head back into the acetabulum, or to keep it from slipping out of the socket. In these cases, surgery is required to repair the injury.
Surgical options include joint capsule or round ligament reconstruction (toggle pinning), total hip replacement (THR), or femoral head/neck ostectomy (FHNO). The specific surgical repair technique will depend on the nature of the injury and the preference of the veterinary surgeon.
What post-operative care does my cat need?
If your veterinarian can place the femoral head back into the acetabulum without surgery, your cat will need to be confined to strict cage rest and may have a specialized bandage to keep the leg motionless and supported. These types of bandages have a high risk of complications in cats so check the bandage and leg daily for swelling, odor, and discomfort. Your veterinarian will give you instructions for the care and monitoring of any bandages.
Depending on your dog’s condition, your veterinarian may also recommend rehabilitation exercises such as passive range of motion (PROM), initially starting with regular movement of the toes, and may perform PROM exercises on your cat’s hip joint when the bandage is replaced.
If your cat requires surgery, there are many techniques that might be used to repair the dislocation. A bandage or support may be placed, depending on the type of surgery, and it will be necessary to restrict your cat as directed by your veterinarian. Whether your veterinarian uses surgery or not, pain medications will be necessary.
What is the long-term prognosis for my cat?
If the femoral head is successfully re-placed and the correct post-operative treatment has been followed, it is unlikely that the hip will dislocate again. In many cases, the hip joint will regain full function and require no further treatment. However, some cats may develop a stiff or arthritic hip months or years after the dislocation, which may require additional treatment.
Cats that cannot have the joint successfully re-placed should be managed with pain management and rest. Your veterinarian will review options for surgical intervention or ongoing conservative care.
Cats that are managed conservatively or that have chronic hip dislocation must be monitored closely for signs of deterioration, including:
- Abnnormal gait
- Decreasing willingness to jump
- Decreasing muscle mass
- Decreasing range of motion
Have your veterinarian assess your cat regularly and discuss any changes that you notice so they can help you determine the best way to keep your cat comfortable with medications, supplements, physical therapy, and/or surgery.
