The Cause of Lameness in Horses

Lameness is a widespread problem among horses of all ages, breeds, and genders. In fact, lameness is identified as the most common cause of reduced performance and training failure in racing, accounting for more lost performance days than any other disease problem. Laminitis or “founder” is a specific foot condition which can cause lameness. This condition weakens the connection of the hoof wall to the coffin bone as a result of inflammation and the destruction of cellular bonds [1].

Figure 1. Model of Blood Vessels in a Horse Hoof

Disturbed blood circulation is generally accepted as the root cause of these problems, since impeded blood flow results in the death of tissues [2]. The idea that problems with blood flow are the cause of laminitis and navicular disease originated in the late 1800’s. Since then, research has shown that blood takes a significantly longer time to flow through the legs and hooves in horses with navicular disease than normal horses [2]. This congestion in the blood vessels can also cause high blood pressure, resulting in arterial disease. Shoeing, exercise, and anticoagulants like warfarin are current treatments aimed at improving blood flow in horses with lameness issues. Thick blood can cause congestion in the blood vessels and the destruction of the navicular bone, a key bone in the foot; on the other hand, healthy blood flow will stop this degradation [3].

Lameness is particularly troublesome and painful for a horse during exercise. Beyond simply stressing the damaged bone and tissues, increasing amounts of red blood cells that are dumped into circulation by the spleen further thickens the blood and restricts flow [4]. (You can learn more about this natural blood boosting mechanism by reading other Featured Articles at Equine Health Labs.) A team of veterinary scientists at Oklahoma State University have stated that improving blood flow in horses with laminitis may reduce pain in the forelimbs similar to the way that blood viscosity reduction can relieve pain for humans with sickle cell crisis [3].

Blood viscosity testing is the only direct way to measure the ability of blood to flow. We offer the Equine Blood Viscosity Test to allow veterinarians, trainers, and owners to screen and monitor blood flow in horses. By measuring systolic and diastolic blood viscosity, we are able to determine the thickness and stickiness of blood. This measurement identifies the underlying circulatory issue which causes or aggravates lameness.


1. Wineland, N., Lameness and Laminitis In U.S. Horses. 2000, United States Department of Agriculture, National Animal Health Monitoring System.

2. Amin, T.M., et al., Effects of warfarin on blood rheology in navicular disease. Res Vet Sci, 1986. 40(3): p. 308-12.

3. Erkert, R.S. and C.G. Macallister, Isoxsuprine hydrochloride in the horse: a review. J Vet Pharmacol Ther, 2002. 25(2): p. 81-7.

4. Stoiber, B., et al., Whole blood, plasma viscosity, and erythrocyte aggregation as a determining factor of competitiveness in standard bred trotters. Clin Hemorheol Microcirc, 2005. 32(1): p. 31-41.