What is Hip Dysplasia?
The very first step in the development of arthritis is articular cartilage (the type of cartilage lining the joint) damage due to the inherited bad biomechanics of an abnormally developed hip joint. Traumatic articular fracture through the joint surface is another way cartilage is damaged. With cartilage damage, lots of degradative enzymes are released into the joint. These enzymes degrade and decrease the synthesis of important constituent molecules that form hyaline cartilage called proteoglycans. This causes the cartilage to lose its thickness and elasticity, which are important in absorbing mechanical loads placed across the joint during movement. Eventually, more debris and enzymes spill into the joint fluid and destroy molecules called glycosaminoglycan and hyaluronate which are important precursors that form the cartilage proteoglycans. The joint's lubrication and ability to block inflammatory cells are lost and the debris-tainted joint fluid loses its ability to properly nourish the cartilage through impairment of nutrient-waste exchange across the joint cartilage cells. The damage then spreads to the synovial membrane lining the joint capsule and more degradative enzymes and inflammatory cells stream into the joint. Full thickness loss of cartilage allows the synovial fluid to contact nerve endings in the subchondral bone, resulting in pain. In an attempt to stabilize the joint to decrease the pain, the animal's body produces new bone at the edges of the joint surface, joint capsule, ligament and muscle attachments (bone spurs). The joint capsule also eventually thickens and the joint's range of motion decreases.
No one can predict when or even if a dysplastic dog will start showing clinical signs of lameness due to pain. There are multiple environmental factors such as caloric intake, level of exercise, and weather that can affect the severity of clinical signs and phenotypic expression (radiographic changes). There is no rhyme or reason to the severity of radiographic changes correlated with the clinical findings. There are a number of dysplastic dogs with severe arthritis that run, jump, and play as if nothing is wrong and some dogs with barely any arthritic radiographic changes that are severely lame.
What are you doing to stop it?
Progress in hip joint phenotype of dogs in the United States between the 1970's and early 1990's has been shown through results of a retrospective study using the OFA data base. This improvement was evident as an increase in the percentage of dogs classified as having excellent hip joint phenotype and a decrease in the percentage of dogs classified as having hip dysplasia (HD). The increase in percentage of dogs classified as having excellent hip joint phenotype was greater for German Shepherd dogs, Golden Retrievers, Labrador Retrievers, and Rottweilers than for all dog breeds combined. In addition, the submission screening rate for these four breeds was higher than the screening rate for all dogs. Within these four breeds, the improvement was greatest for Rottweilers, which also had the highest screening rate.
Overall, low screening rates for breeds found in this study offer some insight into the problems involved with reducing the incidence of HD. The typical dog breeder is involved in breeding dogs for about five years. Thus, informed, experienced breeders are continually replaced with uninformed, inexperienced breeders who may not be as aware of the problems associated with HD or of the importance of participating in a screening program. In addition, many breeders choose which dogs they breed on the basis of the hip phenotype of individual dogs without knowledge of the phenotype of related dogs or previous offspring. It can be very difficult to get hip information on siblings and previous offspring due to the overall low number of dogs radiographed in a given litter (most dogs in a litter end up in pet homes). This is the slowest method of reducing the incidence of an undesirable trait or increasing the incidence of a desirable trait. The use of preliminary radiographs as early as 4 months of age can be used by breeders to add valuable information on the hip status of dogs they choose to use in a breeding program.
What can breeders do?
Hip dysplasia appears to be perpetuated by breeder imposed breeding practices, but when breeders and their breed clubs recognize HD as a problem and establish reduction of HD as a priority, improvement of the hip status can be accomplished without jeopardizing other desirable traits. Prospective buyers should check pedigrees and/or verify health issues with the breeder. If suitable documentation is not available, assume the worst until proven otherwise.
Do not ignore the dog with a fair hip evaluation. The dog is still within normal limits. For example; a dog with fair hips but with a strong hip background and over 75% of its brothers and sisters being normal is a good breeding prospect. A dog with excellent hips, but with a weak family background and less than 75% of its brothers and sisters being normal is a poor breeding prospect.
OFA's Recommended Breeding Principals
- Breed normals to normals
- Breed normals with normal ancestry
- Breed normals from litters (brothers/sisters) with a low incidence of HD
- Select a sire that produces a low incidence of HD
- Replace dogs with dogs that are better than the breed average
My dog has it, what do I do?
Once osteoarthritis is present on a radiograph, dysplastic changes are irreversible and usually continue to progress over time. If a dysplastic dog has secondary arthritis and pain, most owners elect to first treat their dog with medical management. The key to medical management of arthritis is weight control and exercise management. Studies have shown that up to 76% of severely dysplastic dogs with arthritis secondary to HD are able to function and live comfortable quality lives with conservative management.
With weight control, the goal is to prevent the dog from becoming overweight to reduce mechanical stresses applied to the hip joints. In general terms, the ribs should be easily palpated and there should be an indentation in front of the pelvic wings (waist line).
Controlled exercise is indicated to prevent or relieve the inflammatory process that leads to the pain associated with arthritis. The amount and difficulty of the activity is determined on a trial and error basis. Exercise should start with short leash walks and be gradually increased until the dog reaches the desired level of activity. If clinical signs start to reappear, the amount of exercise is scaled back to a level that will not cause clinical signs. Overall, exercise should fit to an individual dog's maximum intensity level with the goal to maintain muscle tone and cardiovascular function without causing pain, stiffness, and inflammation to the joint. The right amount of exercise helps to maintain muscle tone and strength and stabilizes the unstable dysplastic joint. Exercise also improves joint range of motion which in turn, keeps the dog more comfortable. Swimming, because it is a non-weight bearing exercise, can be a very useful means of maintaining muscle tone and range of motion without placing concussive forces on the joint.
Keep the dog in a warm environment. Warmth tends to help control the pain of arthritis from hip dysplasia. As in people, arthritic pain in dogs tends to be worse in the damp and cold of winter. Providing a well-padded and warm bed will help alleviate some of the pain associated with osteoarthritis. An egg-crate foam bed for dogs is commercially available. Applying superficial heat in the form of heating pads may also relieve pain. Care must be taken not to burn the skin especially with an electric heating pad. Heat works best for chronically inflamed joints from arthritis while cold works better to treat acute (sudden) types of joint injury.
Numerous drugs are available to control the signs of osteoarthritis secondary to HD. Nonsteroidal anti-inflammatory pain relievers can be used during bouts of lameness. These drugs inhibit prostaglandin release which decreases the inflammatory process and therefore, less pain is produced. These medications can also be given an hour or so before known periods of exercise to decrease inflammation. Side effects may be seen in some dogs which include vomiting, diarrhea, and inappetence.
Various alternative drug therapies known as disease-modifying osteoarthritis agents can be used. According to the manufacturers, these drugs work by providing the raw materials to enhance the synthesis of glycosaminoglycan and hyaluronate that cannot be adequately produced in the diseased arthritic joint. These are the molecules that form proteoglycan, which is an important constituent of the hyaline cartilage that lines the joint. These drugs may also enhance the synthesis of other macromolecules by cartilage cells that inhibit degradative enzymes produced within the arthritic joint. Controlled studies have been reported about the positive effects in people for osteoarthritis. No controlled studies, to date, have been reported on the clinical response when treating arthritis in dogs but clinically most dogs seem to respond.
Oral disease-modifying osteoarthritis agents known as nutraceuticals are now on the market. These drugs take approximately one month to reach therapeutic levels in the blood stream. Minimal to no side effects have been reported with their use.
Injectable disease-modifying osteoarthritis agents can be injected into the joint, vein or muscle and have been shown to be a useful adjunctive treatment for osteoarthritis in dogs. Since these drugs are injected, more rapid therapeutic levels are obtained. They may be initially used with the oral nutraceuticals for a series of injections for one month since the oral agents take approximately one month to reach therapeutic levels. The literature indicates that the earlier these drugs are administered, the more likely it will decrease inflammation and protect against cartilage degradation in osteoarthritis.
The use of these drugs should be tailored for the individual dogs and any improvement noted. If side-effects occur like GI upset, the medication should be given with food or discontinued altogether. If there is persistence of obvious lameness/pain after approximately 6 months using one medication, change the therapy to a different medication from the above choices.
In younger dogs usually less than 10 months old with only subluxation caused by dysplasia, a triple pelvic osteotomy (TPO) can be performed to reestablish joint stability and encourage normal joint development and minimize abnormal biomechanical forces on the joint before osteoarthritis occurs. This procedure is not indicated if osteoarthitis is already present. Recovery time is about 6 weeks and a good success rate has been reported with return of normal hip function.
For older dogs (over 10 months) that already have established osteoarthritis and can no longer be medically managed, a total hip replacement is the treatment of choice for reestablishing normal, pain-free limb function and joint mechanics. A high degree of success has been reported with this surgery and like the TPO, post-op recovery is about 4-6 weeks. The main disadvantage to this surgery is the high cost.
An alternative surgery which is more of a salvage procedure when there is significant osteoarthritis and a total hip is cost prohibitive is a femoral head and neck excision. This eliminates hip pain by removing the femoral head and neck and initiating the development of a fibrous false joint that permits ambulation. The false joint is less stable with a reduced range of motion than the normal joint which in turn, causes an abnormal gait. Nevertheless, pain relief with adequate function can be achieved. The procedure can be performed in all dogs of all sizes, but there are usually better long-term success rates in smaller dogs less than 20 kg (about 44 pounds). Preoperative muscle mass and early postoperative physical therapy are two important factors in determining a successful outcome. This surgery is usually not as successful if there is severe disuse muscle wasting (atrophy) present and/or the animal is obese.
Heavier dogs usually require more extensive postoperative rehabilitation to help promote an ambulatory pain-free false joint. Rehabilitation is aimed at preserving and promoting the leg's muscle mass, strength and range of motion through early (3-5 days) postoperative weight bearing ambulation and passive range-of-motion exercises. Early ambulation can be achieved by assisting the dog in getting up and walking. A towel can be placed under the abdomen to make assistance easier to perform in heavy dogs. Leash walks and/or swimming beginning the day of discharge from the hospital should be performed until near normal use of the leg returns. Passive range of motion physical therapy is also necessary to increase muscle strength and flexibility. Dogs that are obese, inactive or have substantial muscle atrophy and have poor owner compliance with physical therapy recommendations are poor candidates for this surgery.
**Please note... All info above has been taken from the OFA website & full credit is given to them in their continuing endeavours to make all breeds healthier. Hip dysplasia is not just limited to Mastiffs!**