Joint Disorders in Horses

Traumatic arthritis occurs after an injury. It includes inflammation of the synovial membrane (synovitis) and joint capsule (capsulitis), chip fractures within the joint, tears (sprains) of ligaments near or within a joint, or meniscus (cartilage within the stifle) tears. Gradual loss of cartilage of the joints, known as osteoarthritis, can occur with any or all of these injuries. Traumatic arthritis may be seen in any horse but typically occurs in horses that are athletes. A similar condition occurs in human athletes that undergo traumatic or repeated injury of a particular joint, such as the knee.

Arthritis generally results in pain and altered function of the joint. In its early stage, excess fluid enters injured joints, which can make the surrounding tissues swollen and warm. In more severe cases, manipulation of the joint causes pain. The chronic stage includes a general thickening and scarring of connective tissue, which reduces the range of joint motion. The horse’s gait may change mildly, or it may become severely lame.

Veterinarians take x-rays to exclude other traumatic conditions, such as bone disease or fractures in bone or cartilage.

Treatment of traumatic joint inflammation includes rest and physical therapy regimens such as cold water treatment, ice, passive bending of the joint, and swimming. Nonsteroidal anti-inflammatory drugs are routinely prescribed to relieve pain and inflammation; corticosteroids may be recommended in some cases. There are also a variety of additional medications that may help reduce inflammation and protect the joint cartilage. In more severe cases, a veterinarian will flush the joint to remove any inflammatory or cartilage debris. This is more effective than joint drainage alone.

Arthroscopic surgery may be recommended to remove fragments of bone and cartilage (most commonly seen in the carpus and fetlock) to minimize the ongoing development of osteoarthritis. After such surgery, 2 to 6 months of rest follows, with physical therapy during the recovery period. The success rate in returning horses to previous performance levels is high if the degeneration is minimal at the time of surgery.

In osteochondrosis, the immature joint cartilage separates from the underlying bone. Fluid enters the space, and cysts may form under the cartilage. The cartilages remain attached as a flap or may break away completely ("joint mice"). Osteochondritis dissecans usually is seen in young animals (less than 1 year old), most commonly at the femoropatellar (stifle) joint, tarsal joint (hock), fetlock joints, and the shoulder. The exact cause is unknown but contributing factors likely include a genetic predisposition in the animal, rapid growth, high carbohydrate intake, disproportionate levels of copper and zinc in the diet, and biomechanical factors (such as trauma to the cartilage).

Cysts beneath the cartilage, called subchondral cysts, occur in the femorotibial joint (stifle) and in the fetlock, pastern, elbow, shoulder, and distal phalanx (coffin bone) of horses. Lameness is the usual sign. Levels of excessive joint fluid vary, so the veterinarian will pinpoint the source of the horse's lameness with an examination and, possibly, the use of local anesthetic blocks. X-rays are necessary to confirm the diagnosis.

Surgery using an arthroscope is currently recommended in the femorotibial joint whenever a complete cyst is present. Smaller cysts are treated conservatively at first. Athletic soundness is achieved in 65 to 70% of these horses. More recently, some horses have been successfully treated with an injection of corticosteroids into the cyst.

Infectious, or septic, arthritis is caused by bacterial infection in a joint. Infection may occur after a traumatic injury, surgery, or injections, or it may enter the joint through the bloodstream. Bloodborne infections are more common in foals. A common example is called navel ill, in which the infection reaches the foal through the umbilical cord. Infections in a horse’s digestive tract or lungs can also travel to a joint through the blood.

Septic arthritis usually produces severe lameness and swelling of the joint. When fluid from the joint is obtained and examined, it is cloudy and contaminated. In foals, the infection often inflames the bone and bone marrow.

Septic arthritis must be treated promptly to avoid permanent damage. Infections are treated with injectable broad-spectrum antibiotics, as well as antibiotics injected directly in the joint. Nonsteroidal anti-inflammatory drugs may be prescribed as well. Other useful therapies include flushing the joint with saline solution and cleaning and draining the joint with an endoscope. The effectiveness of treatment is monitored carefully by watching for signs and repeating the examination and analysis of the joint fluid.

Osteoarthritis, which is sometimes called degenerative joint disease, is a progressive deterioration of the joint cartilage. It represents the end stage of most of the other diseases discussed above, such as traumatic arthritis involving the synovial membrane and joint capsule, joint fractures, traumatic damage to cartilage, osteochondrosis, cysts beneath cartilage, and infective arthritis.

Osteoarthritis produces lameness. There may be varying degrees of excess fluid in the joint, an abnormal thickening and scarring of the membranes, and restricted motion of the involved joints. X-rays show decreased joint space, bony outgrowths, inflammation of the muscles or tendons, and a hardening and thickening of the tissue below the cartilage. In less severe cases, an endoscope is used to observe the degree of joint damage.

Treatment of osteoarthritis focuses on breaking the cycle of inflammation in the joint, thereby reducing pain and preserving cartilage health and function of the of the entire joint. These medications may be given by mouth, by IV or IM injection, or by direct injection into the joint. Regenerative therapies, such as PRP and stem cells, can also be useful in treating arthritis. Just as in people, arthritis is progressive and cannot be cured; the treatment goals are to slow the progression and maintain comfort and function. Depending on the severity of the arthritis, adjustments may need to be made to the amount or type of work the horse does, as well.

Capped elbow and hock both involve the development of a bursa in an area where one was not previously present (acquired bursitis). Bursas beneath the hock and elbow can become inflamed if a horse suffers trauma from falling, kicking its stall, from lying on poorly bedded hard floors, riding a trailer tailgate, wearing iron shoes that project beyond the heels, or from leaning or lying down for long periods of time.

Capped elbow and hock rarely cause lameness, but fluid-filled swellings may develop on and around the affected bursa. The bursa may be soft at first but is soon surrounded by a fibrous capsule, especially in the case of a recurrent, older injury. The amount of initial swelling may vary. Infection may occur in longterm cases.

If detected early, the condition may respond well to applications of cold water, followed in a few days by fluid drainage and a corticosteroid injection by your veterinarian. The bursa may also be reduced in size by ultrasonic radiation therapy. Another method involves the application of a substance called a counter-irritant that irritates the skin and thereby reduces the inflammation of the bursa. Older bursas are more resistant to treatment. Surgery is recommended for advanced longterm cases or when infection is present. If a capped elbow has been caused by the heel or the shoe, a shoe-boil roll should be used to prevent reinjury. For a capped hock, modifying the horse’s behavior so it does not kick the stall may offer the only hope of a permanent solution.