Arthritis in Horses

About Arthritis

Arthritis is a progressive and permanent deterioration of articular cartilage, specifically the type of cartilage that lines the ends of bones where they come together to form a joint. Healthy articular cartilage produces a smooth, slippery surface that allows free movement and contributes to the shock-absorbing properties of the joint. As arthritis sets in, articular cartilage becomes compromised, which disrupts the normally smooth surface, causing stiffness and discomfort.

Arthritis is one of the most common conditions that affect performance and pleasure horses. In fact, arthritis is believed to be responsible for up to 60% of all lameness. The joints most often affected by arthritis include the knee, fetlock, coffin and pastern (often referred to as “ringbone”). Whether the condition appears suddenly after trauma or gradually with worsening stiffness, it means the same thing. Chronic inflammation has led to permanent degradation of the cartilage in a horse’s joints, damage which is irreversible.


Joints have several components:

Collateral ligaments – Prevent lateral movements of the bones

Synovial fluid – Fills the space between the bones and provides lubrication and nourishment to the cartilage

Joint capsule – Stabilizes the joint

Synovial membrane – Regulates the joint fluid

Articular cartilage – The soft structural tissue that covers and cushions the ends of the bones


A 1999 study published in the Equine Veterinary Journal concluded that arthritis was a natural part of the aging process in horses. This means that it is not just horses in heavy work that are at risk – all horses are at risk for developing arthritis, even those in light work or no work at all.

Joint damage can be categorized into distinct stages:

  • Synovitis
  • Degenerative joint disease
  • Osteoarthritis

Synovitis is inflammation of the synovial membrane. The primary cause of synovitis is overstretching of the synovial membrane during demanding exercise. Swelling due to an increase in joint fluid production is the most obvious sign. This accumulation of fluid is called joint effusion, common in racing thoroughbreds and other horses worked strenuously. Synovitis can usually be calmed with a layoff from strenuous exercise.


Degenerative joint disease (DJD) can occur if synovitis goes untreated, causing damage to the cartilage surface to develop. This deterioration of the cartilage is the next stage of articular breakdown. DJD is characterized by chronic, progressive degeneration of the joint cartilage and is found most frequently in the fetlock and knee, but is also diagnosed regularly in the pastern and hock. Two primary processes lead to DJD:

  • Repeated bouts of synovitis causing the quality of joint fluid to decrease until it is watery and ineffective in protecting the cartilage
  • Recurring and excessive compression of the cartilage such as that associated with speed, landing after a jump and quick stops. The cartilage becomes rough and flattened, losing all ability to withstand compression

Osteoarthritis is distinguished from DJD by changes in the bone that comprise the joint. These changes severely impede mobility and soundness. The inflammation process goes largely unnoticed unless significant swelling is present.

There are several different types of arthritis in horses, but the most commonly reported are:

  • Osteoarthritis
  • Infectious arthritis
  • Traumatic arthritis


Common Causes of Arthritis

Arthritis is caused by the slow wearing of cartilage. Over time, compression and stress wear away the protective cartilage. Causes of arthritis include:

  • Repetitive and excessive force on a joint may wear down the supporting tissue of the joints
  • Physical injury triggers inflammation
  • Poor conformation may cause abnormal forces, placing addition strain on joints
  • Bacterial infection (septic arthritis) will stimulate an inflammatory response
  • Dislocation and fractures in the joint will result in some degree of arthritis
  • Excessive weight, which causes severe trauma and wear on the joints
  • Hoof deformities and problems with trimming or shoeing can be contributing factors



Diagnosing Arthritis

It is best to look for and discover the disease early since treatment is much more effective in the early stage. Arthritis onset may not be obvious as signs may be absent or there may only be a little joint swelling which is easy to miss.

Indications arthritis is developing include:

  • Slight puffiness in lower leg joints
  • Stiff and awkward gait at the start of exercise, improving as the horse warms up
  • A reluctance to perform movements that used to be done with ease
  • Grating sound when the joint is used
  • Bumps and swellings on joint extremities
  • Stiffness after sleeping or prolonged standing
  • Physical examination can detect swelling, heat and tenderness. Comparing the affected limb to a similar joint can indicate variations
  • A flexion test is useful in determining which joint is affected as subtle lameness often becomes move visible (hold the leg tightly flexed for a minute, then trot the horse on a firm surface)

Managing Arthritis

It is important to be proactive to minimize joint damage and prevent DJD. Activities that can assist in the management of arthritis include:

  • Use nutritional supplements, principally hyaluronic acid which can restore the quality and viscosity of the synovial fluid and improve nutrition of the cartilage
  • Regular exercise helps if it is tailored to the horse’s condition. This increases circulation, tones the muscles and a fit horse has thicker and healthier cartilage covering the joints

  • Remove the horse from a stall. The movement of walking helps the joint fluid circulate as the joint cartilage is compressed and released
  • Altering the diet may help if the horse is overweight
  • Do stretching exercises along with an extensive warm up before exercise. This increases blood flow and warms up and softens muscles and ligaments

Treatments for Arthritis

Early treatment is extremely important and often has excellent results. Many cases of joint pain and inflammation can be successfully treated with a combination of rest and medication, including nutritional supplements. Treatments often include:

  • Nutritional supplements – Glucosamine chondroitin and MSM are frequently used. However, there is conflicting data surrounding their use. Hyaluronic acid, which is the most important component of joint fluid, may improve the quality and viscosity of the joint fluid and assist in preventing the advancement of degenerative joint disease
  • Anti-inflammatory drugs – Prescription NSAID’s are strong and effective anti-inflammatories and pain killing drugs. Because of potential side effects, careful adherence to dosing quantity and frequency must be followed
  • Corticosteroids – Act as potent anti-inflammatories, but unfortunately, have many undesirable short and long-term side effects
  • Acupuncture – Commonly used by homeopathic veterinarians, it is often used in conjunction with NSAID’s, diet and exercise
  • Massage and chiropractic – Can provide significant relief to some horses
  • Hyaluronic acid injections – A series of injections into the affected joints to improve the joint fluid are given over several weeks, very often having favorable results. The cost and inconvenience of multiple injections are a deterrent to many owners. Clinical studies in humans and horses support the use of hyaluronic acid


  • Polysulfated glycosaminoglycans – Administered as a series of weekly injections, may help prevent the breakdown of cartilage and help with the synthesis of new cartilage

Cost of Treating Arthritis

In the United States, the cost of treating arthritis is estimated to range between $1,000 and $4,000 per occurrence and average $2,500. Consequently, a prevention plan including regular examination and use of nutritional supplements can be a cost-effective way to minimize future treatment costs.