Osteoarthritis in the horse is a well-recognized but, as yet, not a fully understood disease.Osteoarthritis leads to the destruction of articular cartilage and there still are no effective means of repairing the damage. Medical treatment of osteoarthritis aims at reducing inflammation and clinical signs caused by the disease. Intra-articular medications used in the treatment of osteoarthritis include corticosteroids, hyaluronic acid and polysulphated glycosaminoglycan and more recently also interleukin-1-receptor-antagonists. Systemic therapies such as non-steroidal anti-inflammatory drugs are discussed in the second part of this review.