Adequan® i.m. is a widely used injectable medication for the treatment of arthritis and other joint disorders in horses. It is the only FDA-approved polysulfated glycosaminoglycan (PSGAG) for equines.

Arthritis is a degenerative joint disease that can reduce athletic performance, cause lameness and lead to early retirement. [1] An estimated 60% of lameness in horses is associated with arthritis. [2]

Adequan® injections are reported to improve pain and lameness scores in affected horses, leading to better mobility. It is purported to work by stimulating cartilage repair, restoring lubrication, and inhibiting processes that break down connective tissue. [3]

Whether your veterinarian recently recommended PSGAGs for your horse or you are investigating treatments to support your horse’s joint health, it is important to understand how Adequan® i.m. works and the directions for use.

Adequan® i.m. for Horses

Adequan® i.m. is primarily indicated for the treatment of non-infectious degenerative joint disease (DJD), such as osteoarthritis and traumatic arthritis in the knees and hocks of horses. [3]

Adequan® i.m. is used in various equestrian disciplines, including racing, performance, and pleasure horses. This medication can be used as a standalone therapy or with other interventions, including exercise management, physical therapy, and other joint supplements.

The medication is administered as a series of intramuscular injections, typically given every four days for four weeks. This injection series may need to be repeated based on reoccurrence of symptoms. Adequan® is also available for intra-articular injections into the affected joint, however, veterinarians are reluctant to use this method of administration due to a higher risk of infection. [4]

The active ingredient in Adequan® is a polysulfated glycosaminoglycan (PSGAG), which acts as a disease-modifying osteoarthritis drug (DMOAD). Research shows that PSGAG reduces inflammatory mediators and enhances collagen synthesis within joints. [3]

Although Adequan® has been a front-line treatment for joint disease for decades, there is a lack of research on the underlying mechanisms of action for this drug.

Consult with your veterinarian to determine if Adequan® is appropriate for your horse.

Mad About Horses
Join Dr. Chris Mortensen, PhD on an exciting adventure into the story of the horse and learn how we can make the world a better place for all equines.
Apple Podcasts Spotify Youtube
Mad Barn - Equine Nutrition Consultants | Mad Barn Canada

Joint Diseases in Horses

Horses are susceptible to various degenerative and/or traumatic joint dysfunctions, including osteoarthritis and traumatic arthritis.

Arthritis is characterized by inflammation of joint structures, which gradually leads to the degradation of cartilage due to the ongoing inflammatory processes. [2][5]


Osteoarthritis (OA) is the most common form of arthritis and a significant cause of lameness in horses. [4] It is most commonly found in the joints of the knees, stifles, and hocks.

OA involves the progressive loss of articular cartilage, subchondral bone thickening (sclerosis), development of boney growths (osteophytes), and inflammation of the joint lining (synovitis). [6]

This progressive condition is linked to:

  • Normal wear-and-tear on the joints
  • Repetitive movements, particularly those involving excessive force
  • Poor conformation

Traumatic Arthritis

Also known as post-traumatic osteoarthritis (PTOA), traumatic arthritis develops after an injury to the joint, such as a fracture, articular cartilage lesion, or ligament tear. [7]

These injuries lead to inflammation of the joint membranes or capsule, resulting in progressive cartilage degradation.

Arthritis and Equine Joints

Synovial joints are most affected by arthritis, including knees, stifles,