Dogs are highly active animals, and their skeletons and muscles are subject to great stresses. Injuries are fairly common, but muscle and bone tissues have a remarkable capacity for self-repair. Other problems can result from diseases of the joints or bones.
The most common sign of muscle, bone, or joint disorders is lameness, usually, but not always, caused by pain. If your dog becomes lame, you should seek immediate veterinary attention and ensure that your dog rests the injured limb. Adequate rest is vital; any physical activity could turn minor lameness into a chronic, major injury.
Diagnosting the Problem
Finding the cause of lameness is often a challenge. Your vet might take X-rays, do blood tests, analyse joint fluid, conduct an MRI scan, take a biopsy, or conduct an “arthroscopic” exam of a joint using a fine fibre optic endoscope. A technique called nuclear scintigraphy, to scan bone and surrounding tissue, may also be useful. The most common muscle, bone, and joint disorders are described below.
Inherited joint diseases
Some dogs are born with an inherited predisposition to joint diseases, such as hip dysplasia, elbow dysplasia, or avascular necrosis. If you want to avoid problems, steer clear of those breeds that are most susceptible. Always buy your pups from a reputable source, and check that they have been bred to minimize the chances of joint disorders. Do not allow your puppy to become overweight, and avoid physical stress on developing limbs. Feed your dog with a diet specially formulated for fast-growing breeds prone to joint problems. The most common inherited joint diseases include:
- • Hip dysplasia: this painful condition causes lameness in one or both hind legs. The term “dysplasia” means abnormal development, and in hip dysplasia, it is the head of the thigh bone (femur) that does not develop properly. The result is that the femur no longer fits into the socket of the hip, causing wear and tear, and leading to pain and lameness. While genetics plays a role in the onset of this condition, other factors, such as overfeeding during puppyhood, may be equally important. Mild cases of hip dysplasia generally respond well to medication, but more severe problems require surgical correction.
- Elbow dysplasia: most frequently seen in Bernese Mountain Dogs, Labrador and Golden Retrievers, and Rottweilers, elbow dysplasia is really a constellation of different elbow problems including osteochondrosis ( below). Cartilage in the dog’s joints develops abnormally, and can interfere with the movement of the elbow joint. Elbow dysplasia generally occurs during a pup’s growth period between four to ten months of age, causing lameness that worsens with exercise. In most cases, treatment will involve surgery to repair the affected joint. o Osteochondrosis (OC): also known as osteochondrosis dessicans (OCD), this condition affects growing puppies. Pieces of poorly developing and interfere with smooth joint function. This commonly occurs in the shoulders, but also in the elbows, stifles, and hocks. It is often seen in heavy, fast-growing dogs fed high-energy diets.Simple rest is sufficient treatment for some affected individuals, but other dogs benefit from having the floating chips of cartilage removed surgically.
- Avascular necrosis: in toy breeds, such as the Poodle and the West Highland White Terrier, the blood vessels serving the head of the femur are prone to injury. If these vessels are damaged, the head of the femur effectively dies, causing lameness. Also known as aseptic necrosis or Perthe’s disease, this condition usually occurs between 4 and 12 months of age. Surgery is the only treatment for avascular necrosis: the dead head of the femur must be surgically removed to eliminate pain. In the months following the operation, a “false” fibrous joint develops that is surprisingly efficient.
Degenerative jont disease (DJD)
Cartilage is the tough gristly tissue that coats the moving surfaces of joints, acting as both lubricant and shock absorber. When cartilage degenerates,or when it fails to repair itself normally after damage, this results in DJD. Regardless of its cause, the progress of DJD is similar in any joint. The first sign is a reduced ability to physically accomplish activities that previously were possible. As DJD progresses, overt stiffness or lameness develops, which is at first intermittent but eventually becomes permanent. DJD is sometimes inaccurately referred to as “arthritis” – a far broader term for any type of joint inflammation. Treatment for DJD involves controlling the dog’s weight and exercise regimen, and minimizing pain. A dog’s weight should be reduced to within the normal range for its breed and sex. Discuss a suitable calorie-controlled diet with your vet. Moderate, sensible exercise, such as walking or swimming, is necessary to maintain good muscle tone, but avoid strenuous exercise, such as running and retrieving games. Pain is controlled with non-steroid anti-inflammatories, such as meloxicam and carprofen. Both are licensed for chronic use when kidney and liver function is monitored.
There are many commercial nutritional supplements that claim to protect joint cartilage. The most widely available of these are glucosamine and chondroitin. When used regularly over a period of time, these appear to be beneficial. Feeding essential fatty acids (EFAs) found in marine fish oil or linseed oil may also be effective – in some individuals this seems to reduce the need for drugs to control joint pain.
In this rare condition, inflammation affects many joints in the dog’s body. It can be triggered by autoimmune diseases, infection, or hypersensitivity to drugs, especially some of the older antibiotics, such as trimethoprin sulfa. Affected dogs may develop a fever, skin rash, and swollen lymph nodes, as well as inflammation. This disorder usually resolves when use of the offending drug is discontinued.
Joint and bone Infections
Occasionally, bacteria can get into a dog’s joints through penetrating wounds or via the bloodstream. Borrelia burgdorferi, the organism that causes Lyme disease, and other tick-borne infections such as Rickettsia and Ehrlichia can all reach joint cavities. Infections of the joints will cause lameness, but can be easily treated with a prolonged course of antibiotics. Bones are quite resistant to infection, but they are occasionally affected by bacteria like Staphylococcus, which enter from wounds, bites, and foreign bodies, as well as from distant locations via the bloodstream. Acute infection is accompanied by fever, loss of appetite and weight, lethargy, and heat and swelling in the muscles surrounding the site of infection. Bone infection, or osteomyelitis, is treated with six-week courses of antibiotics that specifically act in bone tissue.
Dogs develop a variety of bone tumours, the most common of which is osteosarcoma. This highly malignant cancer is most likely to occur in the long bones of middle-aged, or older, large and giant breeds.
The first sign of a bone tumour is usually lameness and pain. Unfortunately, this type of cancer spreads very easily (see pp.272-3), and by the time a tumour has been found, there is a 90 per cent chance that the cancer will have spread to other parts of the body, such as the lungs and liver.
Removal of the tumour, which usually involves amputation of the limb, remains the treatment of choice for tumours in long bones. This is combined with medication for pain relief. With dramatic intervention, around half of dogs with this form of cancer survive for a year or more.
If your dog sustains a fracture, it is likely to be the result of an accident. Before treating the fracture, it is important to remove the dog and yourself from danger, attend to shock, and if necessary, perform life-saving first aid . Fractures can be open – when broken bone protrudes through the skin – or closed. In a closed fracture, the break is not visible but also causes pain and swelling. Greenstick fractures, common in the bones of young dogs, occur when a bone “bends” – cracking on one side only, and compressing on the other. Fractures of long bones are the most evident, because the dog cannot bear weight on the affected limb.
A complete dislocation, or luxation, occurs if the joint surfaces of two bones become separated; a subluxation is a partial dislocation in which the joint surfaces are only partly separated. Subluxations can often be difficult to diagnose, even with X-rays. In some cases, if a dog is seen shortly after an injury, the dislocated bones can be manually replaced under general anaesthesia. However, if left for too long, a surgical procedure may be necessary to repair the joint
By far the most common ligament injury is to the anterior cruciate (knee) ligament, which is most likely to tear in middle-aged, overweight dogs. The treatment varies according to weight: for dogs of less than 7 kg (15 lb), it may be sufficient to rest the injured leg. In three months, fibrous tissue develops in the joint, effectively repairing it. If this is not successful, and for larger dogs, a surgical repair is usually necessary.
Burised or Torn Muscles
Muscular problems in dogs occur most often where muscle fibres meet nerves, or in the nerves that supply the muscle. Strains, bruising, and tearing are overwhelmingly the most common muscle problems. Bruised, stretched, or torn muscle fibres are difficult to see, especially in dogs with full coats of hair. These forms of damage may be caused by injuries from falling and collision, and also by excessive work or exercise: racing Greyhounds are particularly prone to muscle tears. Minor injuries produce local sensitivity and tenderness, while major damage causes more swelling and greater pain. Parting the hair may reveal reddening caused by muscle damage below. To treat bruised or torn muscles, rest is vital. If the damage is severe, at least three weeks rest may be required. A cold compress, applied to the affected area, can help to reduce inflammation and will minimize pain.
Myasthenia gravis is a congenital, or acquired, deficiency in a chemical called acetylcholine (ACh) that transfers information from a nerve fibre to a muscle fibre. Signs of this condition include physical weakness and low exercise tolerance. Infection by the bacterium Clostridium botulinum (botulism) and tick paralysis can prevent ACh from being released by nerve fibres at their junction with muscle fibres, and can result in paralysis. Fortunately, muscle conditions such as these are very rare.
Natural wear and tear
Over time your dog’s muscles naturally shrink and lose their power. Metabolic disorders elsewhere in the body may affect muscle mass by reducing the amount of nutrients muscles need or producing toxins that damage muscle fibre. If your dog is losing muscle mass for no apparent reason, you should seek the advice of your vet.