THE BASICS:

Hip dysplasia is the most common genetic problem in the canine rear limb.  

Hip dysplasia is basically a malformation of the hip joint.  It can involve the socket (acetabulum), the ball (femoral head), and/or the angle of the femoral neck.

Many scientist believe that the many of the changes in the hip joint are directly related to laxity or looseness in the hip joint, and that the key factor may be the genetic component that produces the laxity or looseness.

CLINICAL SIGNS:

Laxity and malformation of the joint allow the joint to sub-luxation, which is a partial dislocation.   It is this sub-luxation that eventually causes the problems associated with hip dysplasia.

The first clinical signs associated with hip dysplasia may be very subtle.  The immature dog may have an occasional limp in the affected rear limb.  There may be difficulty rising from a sitting position, reluctance to jump, or appear "loose" in the rear limbs.  If both hips are dysplastic there may be no noticeable lameness.  At this point there may be little to no degenerative joint disease (DJD).

The other presentation occurs later in life and there will usually be a definite lameness.  The lameness can be in one hip or both.  By this point DJD or arthritic changes have usually began due to the chronic or continuous sub-luxation.

DIAGNOSIS:

Diagnosis of hip dysplasia can be made as early as 4 months of age.  The relatively new diagnostic procedure call the PennHIP x-ray can detect laxity or looseness in the hips. 

Hip laxity can be detected on physical exam by performing a maneuver that produces a sign called the "Ortolani sign".  The Ortolani sign tests for the sub-luxation that is characteristic of hip dysplasia. An Ortolani sign should not be considered negative until it has been performed with the dog under sedation.  A positive Ortolani sign indicates that there is laxity in the hip and that hip is either already dysplastic or has a high chance of becoming dysplastic in the future.  

Many practitioners are recommending that young dogs be radiographed at the time of their spay or neuter.    This is an excellent time to perform these x-rays since the animal is already under anesthesia.  The PennHip or a routine ventral/dorsal view can be taken. 

In the older animal that is exhibiting rear limb pain, radiographs are warranted to evaluate for dysplasia and to assess the degree of DJD that has developed.  The Ortolani sign may be negative in cases that have already developed extensive DJD.

Routine Radiographs

PennHIP
Distracted View

TREATMENT:

Treatment for hip dysplasia depends on the degree of DJD that has effected the joint.

In the young dog that has not developed DJD a corrective procedure can be preformed.  The procedure is called a Triple Pelvic Osteotomy (TPO).  Essentially the socket is rotated to correct the malformation.  The TPO prevents the sub-luxation and thus future DJD development.

In older dogs that are not diagnosed until after DJD has occurred in the hip joint the TPO procedure is not performed.  At this point medical management with anti-inflammatory and chondroprotective agents are used to decrease the pain associated with the DJD.  Physical therapy can also help if the DJD is not too severe.

After medications have proved ineffective, the only way to alleviate the pain is to either remove the joint and create a "false joint" or replace the joint.  The false joint is a very effective option for most dogs less than 50 pounds.  The procedure is called a Femoral Head Osteotomy (FHO).  The "ball" of the joint is removed and thus there is no bone-to-bone contact to cause pain.  In larger dogs the FHO can be less effective and a better alternative is to perform a Total Hip Replacement (THR).  This is the same procedure done to humans with hip joint disease.

Radiograph of Post-operative TPO