Hip dysplasia is a congenital disease that, in its more severe form, can eventually cause lameness and painful arthritis of the joints. It is caused by a combination of genetic and environmental factors. It can be found in many animals and, rarely, humans, but is common in many dog breeds, particularly the larger breeds.
In the normal anatomy of the hip joint, the thigh bone (femur) joins the hip in the hip joint, specifically the caput ossis femoris. The almost spherical end of the femur articulates with the hip bone acetabulum, a partly cartilaginous mold into which the caput neatly fits. It is important that the weight of the body is carried on the bony part of the acetabulum, not on the cartilage part, because otherwise the caput can glide out of the acetabulum, which is very painful. Such a condition also may lead to maladaptation of the respective bones and poor articulation of the joint. In dogs, the problem almost always appears by the time the dog is 18 months old. The defect can be anywhere from mild to severely crippling. It can cause severe osteoarthritis eventually.
Luxating patella is a condition where the kneecap (patella) moves out of its normal position. Luxating patella is one of the most common knee joint abnormalities of dogs, but it is only occasionally seen in cats. It may affect one or both of the knees. In some cases it moves (luxates) towards the inside of the knee, and in other cases it luxates towards the outside of the knee. Luxation to the inside of the knee is the most common form seen; it is most commonly seen in the small or miniature breeds of dogs such as Poodles, Maltese, Yorkies, and Chihuahuas. Luxations towards the outside of the knee are seen less frequently. It can be present in many breeds, but is seen especially in Newfoundlands.
There are four grades of patellar luxation:
- Grade I- the kneecap can be manually luxated but the kneecap returns to its normal position when the pressure is released.
- Grade II- the kneecap can spontaneously luxate out of position with just normal movement of the knee.
- Grade III- the kneecap remains luxated most of the time but can be manually reduced into the normal position.
- Grade IV- the patella is permanently luxated and can not be manually repositioned
Dogs frequently start with a Grade I or Grade II and worsen over time to a Grade III or IV. Many people are not aware their pet is affected, but a luxating patella can cause pain. Owners may see the pet limp on a rear leg, or they may see them shake a rear leg to try to snap the kneecap back into place.
A serious consequence of patellar luxation is that it predisposes the dog to a rupture of a ligament inside the knee called the anterior cruciate ligament (ACL). ACL ruptures are very painful, at least initially, and usually the dog doesn’t bear weight on the affected leg. Surgery is indicated for any case that is causing lameness or pain. Owners may also elect corrective surgery as a way to prevent an ACL.
The rupture of the cruciate ligament is the most common knee injury in the dog.
This injury has two common presentations. One is the young athletic dog playing roughly who acutely ruptures the ligament and is non-weight bearing on the affected hind leg. The second presentation is the older, overweight dog with weakened or partially torn ligaments that rupture with a slight misstep. In this patient the lameness may be acute or there may be more subtle chronic lameness related to prolonged joint instability.
Your veterinarian will perform an orthopedic exam and take radiographs (x-rays) in order to diagnose this injury. The orthopedic exam involves an analysis of the gait, examination of the joint for swelling and/or pain and the presence of “drawer movement” (the presence of forward instability of the knee joint). Sedation is often required to do an adequate evaluation of the knee, especially in large dogs. Sedation prevents the pet from tensing the muscles and temporarily stabilizing the joint and preventing the demonstration of the drawer sign. Radiographs confirm inflammatory changes in the joint and establish the level of osteoarthritic changes present.
Surgical repair is recommended in most cases to stabilize the joint and prevent further osteoarthritic changes secondary to the joint instability. There are three primary types of surgical repair: intracapsular, extracapsular, and tibial plateau leveling osteotomy (TPLO).The type of surgical repair will be determined by the size, age and activity level of the pet as well as the degree of osteoarthritis already present in the joint. The recovery time and recommendation for physical therapy will depend on the type of surgical repair performed.
The most common type of arthritis is osteoarthritis which can be due to wear and tear on joints from over use, aging, injury, or from an unstable joint such as which occurs with a ruptured ACL (anterior cruciate ligament) in the knee.
The chronic form of this disease is called degenerative joint disease (DJD). It is estimated that 20% of dogs older than one year of age have some form of DJD. One study showed that 90% of cats over 12 years of age had evidence of DJD on x-rays.
Other causes of the inflammation can be infectious. Septic arthritis is caused by a bacterial or fungal infection. Lyme disease or Ehrlichia infection can also cause arthritis. Auto-immune diseases, or what is now called immune- mediated diseases, such as Lupus can cause swollen, painful, inflamed joints. More rarely, tumors can cause arthritis.
Treatment for arthritis should be directed to the inciting cause if possible. Surgery may be needed to stabilize a joint. DJD may be treated with NSAID’s, pain medication such as Tramadol, cartilage protective agents such as glucosamine or Adequan, acupuncture, or as a last resort, steroids. NSAID’s (non-steroidal anti-inflammatory drugs) have many types. In general, it is recommended to use NSAID’s developed for pets, and not ones made for use in people as those are highly likely to cause ulcers in dogs, and most NSAID’s can’t be used in cats.
Heartworm has been diagnosed in dogs in all parts of the world and is actually very common. This may be due to the fact that heartworm has a virtual 100% prevalence rate in unprotected dogs living in highly endemic areas. Heartworm, also known as Dirofilaria immitis, is transmitted by mosquitoes. The mosquito injects a microscopic larvae which grows into an adult worm six to eighteen inches long inside the heart of the affected dog.
The worms can cause mild symptoms, such as coughing, but with time, more severe symptoms such as congestive heart failure, weight loss, fluid build up in the abdomen, fainting spells, anemia, collapse, and death usually occur.
Luckily we have several excellent medications which can prevent heartworm if given as directed. There are oral medications which need to be given monthly, and which also help protect against some intestinal parasites. There is one topical medication which is also applied monthly. An injectable medication, ProHeart, which is administered every six months, is back on the market after being withdrawn for several years.
Even if a dog has been given preventatives, it is still important to have annual checkups for heartworms by doing a blood test. Many people are not totally compliant about giving the preventive medication on time, and no medication works perfectly. If a dog has heartworms and it is given a dose of preventative, there can be a reaction that is detrimental to the dog, even deadly.
Heartworms were once thought to be rare in cats. Now we know the incidence is anywhere from 10% to 50% of the canine rate. Heartworm disease in cats is different than in dogs. Cats usually test negative on the routine blood test done in the hospital, the worms are smaller and usually do not produce microfilaria which are like baby heartworms that circulate in the bloodstream. Veterinarians have to do different tests, sometimes more than one, to diagnose heartworms in cats.
The symptoms in cats are different also. Cats usually have asthma signs or cough, even vomit. Cats can die acutely. The treatment for adult heartworms in dogs is expensive and potentially harmful to the dog. This is why it is much better to just prevent them in the first place. There is not a treatment for adult heartworms in cats. Many veterinarians are now recommending monthly heartworms preventative for cats in addition to dogs, since heartworm can be such a serious problem.
There are many types of mites that infect dogs, cats, and other animals. Mites are microscopic arthropod parasites that, for the most part, infect the skin or mucous membranes. Mites can even be present on birds and reptiles. The most common mites that infect dogs and cats are ear mites, Demodex, scabies, and Cheyletiella.
Ear mites are very common on cats and are occasionally seen on dogs. They live primarily in the ear canals and can cause severe irritation. They are easily transmitted between pets, so if they are found in one pet, all pets in contact should be treated. A different species of ear mite can infect rabbits.
Demodex is a mite that all dogs are exposed to, but only a small percentage of dogs develop skin problems. In young puppies, it usually causes small areas of hair loss especially on the head and front legs. Adult dogs tend to show more generalized symptoms, and usually have more red, itchy skin lesions. Adult dogs that develop Demodex usually have another disease such as hypothyroidism, Cushings, or cancer that suppresses the immune system and allows the Demodex to increase in numbers and cause lesions. It is now recognized that cats have their own species of Demodex, but the disease is much more rare in cats.
Scabies is a skin disease in dogs or people caused by the mite Sarcoptes. Most dogs with this disease are intensely itchy. Scabies is highly contagious, but not all dogs in contact are as itchy. People also have their own species of Sarcoptes; most of their cases are due to the human scabies mite, but it is possible for people to develop lesions from the dog scabies mite.
Cheyletiella species of mites can be seen in rabbits and dogs. It is especially seen in puppies as large flakes of scale and is sometimes called “walking dandruff.” There is no one treatment that will kill all the types of mites discussed here. Your veterinarian can advise you on the various treatments for each problem.