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 (thighbone), which forms the “ball.”
The stability of the hip joint depends on many factors, including:
- How well the femoral head (ball) and acetabulum (socket) fit together
- 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 the 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.
Hip dysplasia, a common developmental disorder in which the hip joint does not form properly, can also predispose a dog to hip dislocation.
What are the clinical signs of a dislocated hip?
Most dogs 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), rotated slightly outwards, and may appear shorter than the other limb.
If the dislocation has been chronic (has occurred over a long time), the dog may only show a subtle lameness, especially small dogs, but they will still carry the limb abnormally and will have decreased muscle.
How is a hip dislocation diagnosed?
Your veterinarian will physically examine your dog and notice that the hip joint is painful when it is moved. Your veterinarian may also feel a grinding sensation (crepitus) when the femur is moved. Because this condition is painful, your dog 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 dog 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 place the femoral head back in the acetabulum. The only exception to this rule is if your dog has some other illness or if other factors make anesthesia too risky. If the hip is left dislocated, a false joint may form and the dog 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 dog 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. Some dogs may not tolerate this bandage well. In this case, your dog must be closely supervised and their activity must be restricted. It is important to ensure that the bandage or support wrap is not too tight and does not distress the dog.
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 indicated 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 dog need?
If your veterinarian can place the femoral head back into the acetabulum without surgery, your dog will need to be confined to strict cage rest and may have a specialized bandage to keep the leg motionless and supported. 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 dog’s hip joint when the bandage is replaced.
If your dog 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 confine your dog 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 dog?
If the femoral head has been successfully replaced, the correct post-operative treatment has been adhered to, and the hip remains in place after 14 days, it is unlikely that the hip will dislocate again. The prognosis after most surgical replacements is good. Careful rehabilitation is recommended to improve hip function and reduce future arthritis.
Dogs that were unable to have the joint successfully replaced often limp or have limited use of the limb. Most of these cases will eventually require treatment for osteoarthritis due to their injury, so other surgical procedures may be recommended, called femoral head ostectomy (FHO) or total hip replacement (THR).
