Joint injections in Horses. Evidence and Experience with steroids, HA and other preparations

Intrasynovial medication, direct administration of any product into a synovial space (joint or tendon sheath) for therapeutic purposes, is a widely used intervention in the treatment of articular pathology and associated lameness in athletic horses. Appropriate management of certain common orthopaedic conditions encountered in racehorses may involve continued training aided by disease-modifying agents administered either intrasynovially or systemically. The adverse clinical outcomes of intra-articular corticosteroid medication may be divided into three areas; complications that occur from injection of product, such as synovial sepsis, and the ability of corticosteroids to mask some of the clinical signs of infection; systemic adverse reactions that may occur from the use of corticosteroids such as laminitis; or acute aseptic inflammatory reactions and the ability of corticosteroids to mask pain that leads to further injury.

Osteoarthritis or degenerative joint disease may develop from abnormal stress placed on normal cartilage, such as cyclic athletic trauma, loss of joint stability from injury or loss of joint congruity. Degenerative joint disease may also develop when normal stresses are placed on abnormal cartilage. Abnormalities of the cartilage may arise following synovial sepsis, osteochondrosis or traumatic synovitis. In many horses, the most common reason for degenerative joint disease to develop is as a result of cyclic trauma from athleticism. Degenerative joint disease has a characteristic appearance of degradation of the cartilage structure with variable amounts of bony remodelling and hypertrophy of cartilage. The cartilage becomes fibrillated and thinned with gross wears lines. This fibrillation indicates loss of proteoglycan from the cartilage matrix. The process of cartilage degeneration is mediated by activation of matrix metalloproteinases such as stromelysin, collagenase and gelatinase. These matrix metalloproteinases are activated and produced by both chondrocytes and synoviocytes. Interleukin 1, prostaglandins and tumour necrosis factor alpha, are primary factors that mediate the inflammatory reaction within the joint. These factors, produced in the synovial membrane, synovial fluid and subchondral bone activate and up regulate chondrocyte and synoviocyte catabolic activity. They are also chemoattraction agents for invasion of inflammatory cells into the joint. [...]