Osteochondritis dessicans (OCD)

[Boss Bengal]

( worth mentioning for the small perentage of cats that might get it. Boss)

Osteochondritis dessicans (OCD) is a hereditary disease that occurs early in the development of some dogs, and less often in horses and cats. The condition is characterized by cracks and flaps in articular cartilage, which cause inflammation, joint instability, pain, lameness, and degenerative joint disease.


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Endochondral ossification is the process by which cartilage on the ends of long bones (e.g., humerus, femur) ossifies, or changes to bone. If cartilage does not calcify properly, it thickens and prevents synovial fluid from reaching cartilage cells beneath it. Without synovial fluid, the cells degenerate and die, causing cracks in the cartilage. The cracked cartilage is weak and does not adequately attach to the bone, and the bone does not reach its full length. During movement, the cracked cartilage causes pits and abrasions to form on the bone.

Cartilage cracks can deepen and one or more small pieces of cartilage may loosen, resulting in flaps that may calcify. Cartilage flaps rub against underlying tissue, causing pain, lameness, and eventually degenerative joint disease.

Sometimes flaps of cartilage detach. In some cases, they are reabsorbed and in others, they float inside the joint capsule, grow, and eventually interfere with movement. "Joint mice" can become wedged between the bones of the joint, eroding cartilage and causing severe pain.

The body attempts to compensate for the damaged cartilage by forming scar tissue or by adding bone to the affected area (i.e., remodeling), increasing instability and irritation.

Incidence and Prevalence
More than 10% of dogs develop OCD in one or more joints. The condition is more prevalent in large and giant breeds such as:

* Great Dane
* Labrador retriever
* Newfoundland
* Rottweiler
* Bernese mountain dog
* English setter
* Old English sheepdog
* Golden retriever
* German shepherd

Other large breeds (e.g., Doberman pinscher, collie, Siberian husky) have a low incidence of OCD.

OCD of the shoulder occurs twice as often in male dogs than in female dogs and OCD of the hock occurs more often in females. The disease occurs less frequently in horses and cats than in dogs.

Causes, Symptoms




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Several genes from both parents combined with other factors determine whether an animal develops osteochondritis dessicans (OCD). Which genes are involved and exactly how OCD occurs are unknown.

Nutrition is the most understood risk factor. A diet high in calcium content increases the risk for OCD. High-calorie diets and rapid weight gain at any age may also contribute to the disease.

Running and walking on hard surfaces (e.g., concrete), trauma from injury, and excessive workload or exercise can cause the cartilage to separate from bone and can result in lesions on the cartilage.

Insufficient blood supply to the joint and hormones, which regulate growth and reproduction, are also associated with OCD and affect development of the condition.

Signs and Symptoms

The most common symptom of OCD is lameness in the limb of the affected joint. Lameness may cause a slight limp or the animal may be unable to bear any weight. It may occur suddenly or it may be chronic, lasting weeks or even months. Rest helps to alleviate the lameness and exercise exacerbates it.

Other symptoms of OCD include:


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* Altered gait
* Crepitus (grating noise of bones rubbing against each other)
* Decreased range of motion
* Limb held with toes pointed outward
* Pain when joint is touched
* Resistance to full extension and flexion of joint
* Swelling

Symptoms usually develop between 4 and 10 months of age, and occasionally later. Mild, intermittent lameness may occur at onset or as late as 18 months of age. Without strict rest, the severity of the lameness increases, can become chronic, and, in severe cases, cause surrounding muscles to atrophy from lack of use.

OCD can develop in several joints. Lesions are often present bilaterally (in the same joint on both side of the body), but lameness usually occurs only on one side of the body. Degenerative joint disease can develop in severe cases.

Complications
OCD is a major cause of elbow dysplasia and commonly occurs with fragmented medial coronoid process.

Diagnosis


Diagnosis includes a physical examination, x-rays, and/or arthroscopy. A physical examination includes a medical history (information about lameness, joint pain, or family history of OCD) and observation of any abnormalities in stance and gait.


The veterinarian palpates (feels) the joint and tests its range of motion. Anesthesia may be necessary to move the limb without causing pain. Several signs may be present including:

* Crepitus (crackling noise of bones rubbing against each other)
* Pain
* Restricted mobility or extension
* Swelling

Testing
Arthrocentesis or joint tap confirms the presence of degenerative joint disease and inflammation. A needle is inserted into the joint, and fluid is withdrawn and analyzed. A high white blood cell count and an opaque consistency of the fluid indicate inflammation; the presence of pus indicates degenerative joint disease caused by infection.

Imaging
X-rays reveal lesions on bones underneath the cartilage, confirm severe cases of OCD, and show signs of degenerative joint disease, but they do not show separation of cartilage or joint mice. If the animal is lame and the radiographs do not show a lesion, the animal is re-examined within 4 weeks. X-rays are also used to assess whether the joint is properly aligned (joint conformation). Sedation may be required for proper positioning of the limb.

Positive contrast arthrography shows soft tissues, including cartilage. A radioactive dye that provides contrast between tissues and bones is injected and the area is x-rayed. The image reveals thickened or separated cartilage, cartilage flaps, and/or joint mice. This procedure carries the risk for exposure to a high level of radiation.

Arthroscopy is a minimally invasive procedure performed with a fiber-optic tube. For diagnostic purposes, a microscopic camera attached to the tube is inserted into the joint so that the entire joint and abnormalities of bones or soft tissues can be seen. Surgical tools can also be attached in order to take tissue samples and to perform other procedures. This is the diagnostic tool of choice, but it has limited availability.

Differential Diagnosis
Veterinarians must rule out several conditions with similar symptoms, including the following:

* Cartilage fractures
* Elbow dysplasia
* Panosteitis (inflammation of every part of a bone)

Since fragmented medial coronoid process (FMCP) [link to FMCP in elbow dysplasia] and OCD can occur simultaneously, the animal is assessed for this condition.

Treatment


The goal of treatment is to alleviate pain, increase mobility, and prevent further damage. Factors to consider when determining treatment include the following:

* Age and health of animal
* Availability of a surgeon
* Cost
* Intended use of animal
* Severity of symptoms



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Conservative treatment is less expensive and requires less rigorous owner compliance than surgery. It is often used for older dogs and those with other health problems. Surgery is performed only on healthy animals, and it requires an experienced surgeon and owner compliance for proper healing. Surgery is often considered for young dogs and dogs used for breeding, showing, and working.

Conservative
Conservative treatment includes rest, confinement for 4 to 8 weeks, and weight control. This treatment is recommended when symptoms are mild and x-rays do not show lesions.

With rest, the cartilage heals and animal often regains full function. If rest alone does not relieve the symptoms, medication may be necessary.

Losing even a small amount of weight reduces stress on the joint. The recommended diet has a low fat, protein, and calcium content, and meals are provide at specific times of the day.

Nonsteroidal anti-inflammatory drugs (NSAIDs) reduce pain and inflammation. They cannot be used in animals with hemostatic disorders (reduced ability to form blood clots).

Buffered aspirin can be used for long-term conservative treatment. Side effects include gastric complications such as ulceration, vomiting, diarrhea, loss of appetite, and bloody stools. Giving the aspirin with food can reduce side effects.

Carprofen (Rimadyl®) is an anti-inflammatory pain reliever used to treat joint pain. Side effects include nausea, diarrhea, constipation, and loss of appetite, and if they occur, the veterinarian should be notified. Tests to monitor liver function may be necessary because long-term use may cause idiosyncratic liver problems. Rimadyl is not given concurrently with other NSAIDs or with corticosteriods because the risk for side effects increases.

Corticosteriods reduce inflammation but have serious side effects such as disruption of adrenal function and suppression of the immune system. They should be used only on a short-term basis to promote healing.

Nutraceuticals
Nutraceuticals, also called dietary supplements, are oral agents that provide health benefits but are not regulated as drugs. Chondroprotective agents, made from extracts of components necessary for cartilage development, are used to promote the development of new cartilage and strengthen existing cartilage. Two chondroprotective agents used to treat arthritis in humans (chondroitin sulfate and glucosamine) are being used for joint damage in animals. Chondroitin sulfate blocks enzymes that break down cartilage, and glucosamine builds cartilage and may also decrease inflammation.

The supplements are promising but expensive and are available in tablet or capsule. These supplements include SynoviCre®, Glycoflex®, and Arthramine® (all contain glucosamine); Adequan® (contains chondroitin and glucosamine), and Cosequin® (contains chondroitin, glucosamine, and manganese). Glucosamine can be injected directly into the joint or into a vein and works more quickly than the oral form.

An uncommon side effect is gastrointestinal upset; taking the supplements with food can help. If upset continues or if there is no improvement within 6 months, other treatment methods are required. Taking the supplements with aspirin may cause problems in forming blood clots.

Surgery
If conservative treatment does not improve the symptoms, surgery may be performed. The shoulder joint is accessible through an arthroscopic approach in larger dogs, if such equipment and expertise are available. Joint mice and damaged cartilage may be removed through a small incision. If an open approach is used, an incision is made above the joint, the joint is opened, and any cartilage flaps or joint mice are removed with forceps. The surgeon may scrape the cartilage bed to stimulate healing. The joint is flushed and sutured.


Complications
Complications from surgery include adverse reactions to anesthesia (nausea, vomiting, fatigue, and in rare cases, death) and infection. Antibiotics are given after surgery to prevent infection.

After care
The owner should monitor the incision for signs of infection (e.g., redness, swelling, heat, pain) for 2 weeks after the surgery. Fluid may build up at the site of the incision (seroma) and must be drained (aspirated).

Pain medication may be necessary. A cold pack may be applied several times a day for brief periods helps decrease swelling and control pain during the first week.

The animal must rest for 2 weeks and then may be taken for short walks on a leash. Weight control is important to reduce the amount of stress to the joint in older animals. In growing dogs, a restricted diet slows growth.

The animal should have an annual examination to evaluate the presence or progression of degenerative joint disease.

Prognosis, Prevention


Recovery depends on the size and location of the lesion, the amount of erosion in cartilage bed, and the animal's general health and diet. Within 6 to 8 weeks, most animals achieve normal function.


Prognosis for OCD in the shoulder is good to excellent with full function restored after surgery.

Prognosis for OCD in the elbow, stifle, and hock is fair to guarded, depending on the size of the lesion, the severity of degenerative joint disease, and the animal's age. Lameness, months to years after surgery, is common if degenerative joint disease progresses.

Prevention
The only way to prevent osteochondritis dessicans (OCD) is to stop breeding animals that may carry the genes for disease.

A restricted diet may slow muscoloskeletal development during the formative months. Providing a lean diet (low in protein and fat) for the first 2 years may lessen the severity of OCD. Owners should not feed puppies excessive amounts of food or give food that is high in calcium.

Running on hard or slippery surfaces, jumping, and climbing increase stress to the joints and should be discouraged, especially while the muscles and bones are developingt.