Osteochondrosis

Osteochondrosis is a pathological condition in rapidly growing large breed dogs that leads to a painful disturbance in joint cartilage development. In osteochondrosis, the cartilage cells fail to differentiate in a normal manner. The joint cartilage becomes thickened and large, decayed areas develop. At this point, osteochondrosis has occurred and represents one of the true "growing pains" of canine adolescence.

If the puppy is active and traumatizes this soft, decayed area, cracks or fissures form and extend into the normal cartilage until a large cartilage flap forms. This is known as osteochondritis dissecans (OCD). "Osteochondritis" refers to the presence of an inflammatory reaction in the bone marrow and joint, while "dissecans" refers to the flap of cartilage that is formed.At this stage, pain is present in the joint every time the dog tries to walk. When the cartilage flap falls into perfect position, discomfort is minimal. As the cartilage flap shifts position, pain becomes acute with joint swelling that is increasingly sensitive.

The sites most commonly affected include the shoulder, elbow, knee, and ankle (hock). The syndrome can be bilateral and on occasion involves several joints.

SHOULDER JOINT:

Osteochondrosis of the shoulder affects the caudal aspect of the humeral head. It is most often seen in male large breed dogs. Clinical signs include lameness which is worse after exercise and pain on palpation of the shoulder joint. It is seen most frequently in animals between four and seven months of age. Radiographs (x-rays) are used to diagnose the lesion. Early radiographic changes include an abnormal contour or flattening of the humeral head. Later in the disease there is a radiolucent defect in the shoulder joint surface. Treatment for this syndrome is surgery to remove the cartilage flap as soon as it is formed (see Fig. 1).

ELBOW JOINT:

Osteochondrosis occurs in the elbow on the medial condyle of the humerus. It is most common in large or giant breed dogs from four to seven months of age. The clinical signs include acute or chronic intermittent lameness of one or both forelimbs. The treatment of choice is surgery with the prognosis depending on the severity of the arthritis (degenerative joint disease) already present.

STIFLE JOINT:

Osteochondrosis in the stifle (knee) can be difficult to clinically diagnose as the lameness is frequently obscure and is often confused with hip dysplasia. The lesion is seen in x-rays as a flattening or radiolucent defect in the lateral or medial femoral condyle. The prognosis is fair even if surgery is performed early in the course of the disease and is not as favorable as with surgery in the elbow or shoulder.

HOCK JOINT:

Osteochondrosis lesions in the hock occur on the caudal aspect of the medial ridge of the talus bone. Affected animals are usually four to five months of age and present with slight lameness of the hind limbs. The ankle joints appear straight and swollen, and are painful upon flexion and extension. Radiographs demonstrate displaced cartilage, bone fragments, and bone spurs due to secondary degenerative joint disease. The prognosis is good if surgery is performed before the onset of secondary arthritis. Once arthritis is advanced, surgery is helpful in relieving any intense pain but does not afford the results expected with surgery of the elbow or shoulder.

Ununited Anconeal Process

Ununited anconeal process is a failure of the growth center of the anconeal process in the elbow joint to unite properly with the ulna. This fusion should be completed by sixteen to twenty-four weeks of age. Instead of a normal bony union, the ununited anconeal process represents a large piece of bone connected to the ulna by a strand of fibrous tissue. The diagnosis is confirmed by radiography. Surgical removal of this unstable bony fragment minimizes progressive arthritis and is indicated as soon as possible to prevent further joint degeneration (see Fig. 2).

Fragmented Coronoid Process

Older dogs with this syndrome usually have severe arthritis of the entire elbow joint. Again, surgical removal of the unstable bony fragments minimizes progressive arthritis and is indicated as soon as possible to prevent further arthritic changes. While the intense pain and crippling arthritis seen in chronic cases is greatly improved by surgical removal of the coronoid fragments, residual arthritis will require some intermittent antiinflammatory medication.

Panosteitis

Panosteitis is the most common and painful of the "growing pains" with the age of onset usually between five and twelve months of age. It has been reported in dogs as young as two months of age and as old as five years of age. While panosteitis usually affects large or giant breeds of dogs, it can also affect the Basset Hound.

CLINICAL SIGNS:

Clinically, there is pain in the long bones (humerus, ulna, radius, femur, and tibia) which is manifested by slight to severe lameness which can last from a few days to several weeks. Some animals may be reluctant to move at all. Often the lameness shifts from one limb to another every two to three weeks, with apparent lapses in clinical manifestations of up to three months between episodes. Multiple bone involvement is seen in about one-half of the cases. The classic finding on physical examination is pain on deep palpation of the long bones. Some animals may have reduced appetite and activity during the painful periods. The complete course of the disease is usually two to three months, but it can range from a week to six or eight months.

RADIOGRAPHIC (X-RAY) SIGNS:

Ultimately, the diagnosis of panosteitis is made radiographically. A radioisotope bone scan can be used to diagnose those with no radiographic lesions.

THERAPY:

Inasmuch as the cause of panosteitis is not known, only symptomatic treatment is recommended for those animals who need pain relief. Antiinflammatory drugs such as aspirin and corticosteroids are probably the most commonly used agents. The disease will eventually run its course and resolve at maturity.