The Balanced Foot

Jay Jordan
Denise Jones
Dr. Jeremy D. Hubert

Most horse owners would agree that the “foot should be balanced”, but what does “balanced” mean? Balance refers to the relationship of the hoof to the anatomical structures of the lower leg and the relationship of the hoof to the ground. Primarily balance is evaluated medial to lateral (inside to outside) and dorsal to palmar/plantar (front to back) as the horse stands. Balance of the hoof as it deals with locomotion (dynamic balance) relates the concepts of hoof flight, break over and landing. Correct shoeing attempts to compensate for less than ideal conformation and resolve interference and potential lameness issues.

When we observe the leg from either the front or the rear we can evaluate static medial to lateral balance. An imaginary line drawn down the middle of the cannon should divide the hoof into two equal halves. When the horse has ideal leg conformation this will produce the desired result of a foot that will land evenly on the ground. If the horse does not have ideal leg conformation and is base narrow and toed out then the hoof will not land on the ground evenly and the lack of dynamic balance will produce uneven stresses which may lead to lameness. The hoof responds to the lack of medial to lateral balance by abnormal growth patterns such as sheared heels. This condition is diagnosed when there is more than 0.5 cm difference in the height of the heel. The traditional approach to correcting hoof abnormalities such as sheared heals is to trim the flares of the hoof and encourage the growth of the opposite hoof wall by fitting the shoe to the outside of the hoof wall.

The dorsal to palmar/plantar balance as viewed from the side of the horse has three major components. The first component is the hoof - pastern angle. Ideally a line drawn through the middle of the pastern should be parallel to a line following the hoof wall. Some authorities also suggest the angle of the heel should also be parallel with the pastern. When the angle of the hoof wall is less than the angle of the pastern then the axis is said to be broken back. This conformation often leads to navicular syndrome, impeded blood flow to the navicular area, superficial digital flexor tendon strain, increased breakover time and overreaching by the back foot in relation to the front foot. If the condition exists in the hind legs look for soreness in the hocks and back of the horse. When the angle of the hoof wall is greater than the angle of the pastern then the axis is described as broken forward. This conformation is associated with coffin joint arthritis, coffin bone extensor process injury, pedal osteitis and increased strain on the suspensory tendon and the superficial digital flexor tendon. The second component to evaluate is an imaginary line drawn in the middle of the cannon, perpendicular to the ground. This line should just brush the back of the heel where it touches the ground. If the heel contacts the ground in front of this line then the horse has underrun heals. Underrun heals are often associated with the broken back hoof pastern axis and are associated with similar lamenesses. The third component of the dorsopalmar/plantar balance is the toe length which should be approximately related to the weight of the horse. The following chart is a general guide.
Weight (kg)
Toe length (cm)
360 – 400
7.6
425 – 475
8.25
525 – 575
8.9

These dorsopalmar/plantar balance evaluations are intimately involved with evaluating the break over of the hoof. When the toe is too long, the heels are usually underrun and the hoof pastern axis is not straight. This results in excessive stress on the navicular bone and the tendon support structures. Correction of this conformation involves trimming the toe and supporting growth of the heel by extending the heel of the shoe.

Having evaluated the relationship of the leg to the hoof, next the relationship of the hoof to the ground should be evaluated. A line drawn across the widest part of the bottom of the hoof should divide the foot with 1/3 of the sole towards the toe and 2/3 of the sole should be towards the heel. The frog width should be greater than 67% of the length of the frog (width/length > 0.67). A frog which is too narrow indicates contracted heels, a condition associated with either a lack of weight bearing on that foot or a shoe which does not permit the expansion of the heel when weight is placed on it. The weight of the horse should also be taken into consideration when evaluating the size of the hoof. In general a hoof is too small if the weight to hoof area ratio exceeds 78 pounds per square inch. To calculate, estimate the horse’s weight in pounds multiplied by 12.56. Then divide that by the square of the hoof wall circumference in inches measured immediately below the coronary band.

Trimming or shoeing a hoof in balance with the leg and the way that it lands on the ground reduces the risk of interference or lameness. The three key elements to keep in mind regarding foot balance are the hoof- pastern axis, alignment with the front of the cannon bone, and the shape of the sole area that lands on the ground.

References:
Parks A. Examination of the foot, at www.equipodiatry.com/examfoot.htm
Stashak T.S. Adam’s Lameness in Horses 5th ed. Philadelphia: Lippencott Williams & Wilkins, 2002; 1089 – 1097.
Balch O, White KK, Butler D. Factors involved in the balancing of equine hooves. Journal American Veterinary Medical Assoc. 1991; 198: 1980 –1989.
Turner TA, Stork C. Hoof abnormalities and their relation to lameness, in Proceedings. 34th Annual Convention of AAEP 1988; 293-297.
Turner TA. Objective Assessment of Hoof Balance, at www.equipodiatry.com 1999.
Butler KD. The prevention of lameness by physiologically-sound horseshoeing, in Proceedings. 27th Annual Convention of AAEP 1985; 465-475.
Dr. Martin, course notes; LSU-SVM ,VMED 5362, Fall 2001.
Dr. Hubert, course notes; LSU-SVM, VMED 5010 Advanced Equine Musculoskeletal course, Spring 2002.