Today I am going to talk about inflammation of the proximal suspensory ligament in a horse's hindlimb. This ligament is located at the back of the horse's cannon bone, and it starts at the lower part of the hock and inserts on the sesamoid bones near the fetlock. The ligament starts out as a solid sheet of ligament and then divides into two branches; one branch inserts on the inside sesamoid bones and another on the outside. You cannot really feel the suspensory ligament on the back of the leg because it is close to the bone and under the flexor tendons. All areas of this ligament can be damaged in both the front and hind limbs, but the top portion of the ligament just below the hock in the hind leg is particularly problematic.
Until the use of ultrasound, we really had no way of knowing this area was a problem but now with MRIs, damage to this ligament is commonly found. This is a difficult area to ultrasound because it is so deep and it does not always show the damage. It is believed that horses with a straight hock conformation are more susceptible to proximal suspensory ligament injury, and that injury usually occurs with hyperextension of the fetlock joint. Dr. Sue Dyson indicates that a medium to extended trot increases hind limb extension and increases chance of an injury.
These horses are usually mildly to moderately lame and a nerve block to numb the area is required to diagnose the condition. Treatment by surgery is the best option, in which the nerve going to the affected area is cut to decrease pain. Some horses with this condition also have lower back pain and pain in the hock joints, and both of these conditions must be treated to make the horse sound.