DEFINITION:

Osteochondrosis is a term used to describe a variety of joint diseases all of which involve abnormal cartilage-and/or bone development. These diseases can affect the shoulder, elbow or knee joints. Degenerative osteoarthritis will be the outcome of all of these diseases as abnormalities within the joint lead to further wear and tear and joint degeneration. Common lesions are:

Shoulder Joint Lesions

Osteochondritis Dissecans (OCD) of the humeral head
OCD of the glenoid (the “cup” of the scapula that the humeral head fits into)
Abnormal bony development of the glenoid and/or humeral head (shoulder dysplasia)

Elbow Joint Lesions

OCD of the medial humeral condyle
Separation/fragmentation of the medial coronoid process of the ulna
Fissure of the medial coronoid process of the ulna
Separation/fragmentation of the lateral coronoid process of the ulna
Ununited Anconeal Process (UAP)
Abnormal ossification of the distal (farther away from the spinal cord) border medial epicondyle of the humerus
Separation or nonunion of the medial epicondyle
Delayed ossification of the lateral humeral condyle
Delayed ossification of the proximal (closest to spinal column) ulna
Delayed ossification distal humeral epiphysis

Reproduced from Hill’s Atlas of Veterinary Clinical Anatomy

Osteocondrosis Dissecans (OCD): OCD is a disease characterized by separation of a portion of cartilage from bone. All bones within joints are covered with cartilage. The disease begins as the cartilage begins to separate from the bone and forms a “flap”. This flap can cause symptoms on its own. The flap of cartilage can also break free from the bone and “float” about within the joint (joint mouse). The final separation of the flap may be precipitated by a relatively minor trauma and produce an acute onset of lameness. It is also possible for this free piece of cartilage to continue to grow within the joint and impinge on various joint structures.

CLINICAL SIGNS:

Lameness is the presenting symptom. It first occurs between four and eight months of age. Males are approximately three times more frequently affected than females. Lameness may be a sudden event and is usually of a slight to moderate degree at first. It generally worsens with exercise and diminishes with rest. The dog may tend to hold the affected limb in a direction slightly away from the body and may also be reluctant to fully extend the affected joint(s) during movement or upon examination.

DIAGNOSIS:

Physical examination and radiographs of the affected joint(s). The Orthopedic Foundation for Animals does maintain an Elbow Registry. Elbow x-rays are submitted to be evaluated for OCD and UAP. The purpose of this registry is to identify phenotypically normal dogs and screen radiographs for signs of early degenerative elbow joint disease. The earliest and most consistent secondary change is a smooth periosteal reaction on the proximal anconeal process and/or joint incongruity. Dogs aged 24 months or older that have normal radiographs will be assigned a breed registry number. These numbers will be periodically reported to the parent breed club.

Elbow Grading

Grade I:Minimal bony changes of the anconeal process

Grade II:Additional subcondral bony changes and/or presence of osteophytes (bone spurs)

Grade III: Well-developed degenerative joint disease

TREATMENT:

Some OCD lesions never cause lameness and will not require specific treatment. Many dogs will be seen that have disease in both shoulder or both elbow joints radiographically, but will display lameness only to one extremity. This may shift from one limb to the other. Some surgeons believe only 20% of these bilateral cases will require surgery on both sides, whereas others suggest up to 50% require bilateral surgery. In the shoulder, surgical treatment is indicated when lameness is present and persistent and when there is pain upon manipulation of the joint. In the elbow, the OCD lesion involving the distal(furthest away from spinal cord) border of the medial epicondyle can be treated conservatively or with surgery. If more than one lesion is presenting a joint, surgery is indicated. Conservative treatment includes regular exercise with a gradual build-up in the amount of daily exercise. Generally, by the time the dog is twelve to eighteen months of age, the lameness may have resolved on its own.

PROGNOSIS:

The osteoarthritis associated with the lesions of osteochondrosis will progress throughout life. It may not produce symptoms until middle to older age. Once osteoarthritis is present, surgical treatment may actually increase its progression. Surgery should be considered if shoulder or elbow lameness is particularly severe or worsens with a conservative approach. In general, the sooner surgery is done the better the prognosis.

MODE OF INHERITANCE:

Nutritional, environmental and genetic factors have all been implicated. These are diseases primarily of young, fast-growing, active dogs of medium to large size. The nutritional factor is one of over-feeding or over-supplementing growing dogs. The exact mode of genetic transmission is unknown. Owners are encouraged to register their dogs with OFA and breed only dogs deemed normal. In the editor’s opinion, dogs with OCD of any joint should be excluded from breeding programs.

REFERENCES:

Ettinger S., Feldman E. Textbook for Veterinary Internal Medicine Vol. II.

Foster, R., Smith, M. What’s the diagnosis?: understanding your dog’s health problems. New York: Howell Book House, 1995; 70-71.

Gregory, C.R. Surgery and postoperative care. In: Siegal, M., ed. UC Davis school of veterinary medicine book of dogs: a complete medical reference for dogs and puppies. New York: HarperCollins, 1995; 441.

Hill’s Pet Products. Hill’s Atlas of Veterinary Clinical Anatomy. USA: Veterinary Medicine Publishing Co., Inc., 1989: 44, 46.

JAAHA. The inheritance of osteochondritis dissecans and fragmented coronoid process of the elbow joint in Labrador Retrievers. 1994, Nov. 7.

Kirk, C.A., Biourge, V. C. Diseases of dietary origin. In: Siegal, M., ed. UC Davis school of veterinary medicine book of dogs: a complete medical reference for dogs and puppies. New York: HarperCollins, 1995; 109-110.

Leighton, R.L. The skeleton and disorders. In: Siegal, M., ed. UC Davis school of veterinary medicine book of dogs: a complete medical reference for dogs and puppies. New York: HarperCollins, 1995; 266.

Padgett, G. Elbow registry. Columbia, MO: Orthopedic Foundation for Animals.