Heather Smith Thomas
Some horses stumble or stub their front toes frequently, with the toe hitting the ground while the knee is still bent and the leg collapses instead of taking weight. The horse's head and neck drop down, but he usually catches himself by rapidly extending the other leg. Most of these horses are not lame, yet might occasionally fall to their knees or go down with a rider. The habitual stumbler might manage fine when running free, but tends to trip and stumble when being ridden or led. The stumbling horse is frustrating to ride, and he can be dangerous.
Stumbling can be caused by a number of things, including long toes, long feet, hoof imbalance, laziness or boredom, and in some instances devious behavior--a few horses learn they can get out of work if they stumble because a concerned rider thinks there is something wrong and ends the ride. Stumbling can also be due to inadequate conditioning (such as a young horse unaccustomed to carrying a rider, or a horse whose muscles are out of shape), poor conformation, incoordination, joint problems, chronic foot pain, damage to the central nervous system (brain and spinal cord), brain disorders such as narcolepsy (sudden attacks of sleep), or weakness due to fatigue or illness.