Next to the hoof, the most common area of lameness in exercising horses is probably the fetlock or ankle of the horse. Though many causes of lameness in this region are easily seen and diagnosed, lameness originating from here that is difficult to localize on the physical exam is readily localized with the use of perineural anesthesia (nerve blocks), for more information. Careful use of nerve blocks can localize lameness originating from the fetlock and can further define intraarticular and intrasynovial pain from the other causes of lameness in this region. Careful use of regional anesthesia may even localize the pain from particular structures. This article discusses the diseases that occur in the fetlock and their diagnosis, treatment, and prognosis.

The fetlock is the area of the leg often referred to as the ankle and is between the pastern and the cannon, for illustrations. Starting distally and working up the leg the fetlock consists of:

• the upper 1/3 of the proximal phalanx,
• the distal sesamoidean ligaments,
• fetock joint and associated ligaments,
• distal aspect of the 3rd metacarpal or metatarsal,
• the annular ligament,
• the proximal sesamoidean bones
• the attachment of the proximal sesamoidean ligaments,
• the flexor tendons and sheath from the level of the proximal sesamoidean bones down to the proximal pastern.

Other than some minor differences in the way the nerves run, the rear and front pastern are similar enough anatomically that you can refer to them as the same.