The Background - Lameness resulting from joint degeneration or osteoarthritis (OA) is one of the most prevalent diseases affecting horses and the most common reason that vets are called out to competition horses. OA causes inflammation of the joint lining and progressive destruction of articular cartilage that covers the ends of the bones composing a joint. This destruction decreases both the natural shock-absorbing function and the range of motion of the joint, ultimately resulting in lameness in the affected animal.
Howard Wilder (14 October 2008 - Issue 10)

Men have been interfering with the equine larynx for centuries, but so far with only limited success.When a horse is heard to be making a noise for the first time, it is of serious concern. Sometimes the concern is only short lived as the horse may be unfit, have a mild respiratory infection or perhaps a sore throat. However, on other occasions the equine athlete in question is on the verge of being diagnosed with a problem that will limit its performance for the rest of its life.
James Tate BVMS MRCVS (14 October 2008 - Issue 10)