PROCEDURE
Halter the horse and have them stand on a flat, even surface with the hind limbs positioned as symmetrically and squarely as possible when viewed from the rear.
First, standing 10' (3m) away visualize the left hind limb from the left side. Let your eyes begin at the hoof and travel up to the peak of the croup. The hoof angle should roughly match the pastern angle.
Consider the conformation of the limb. Look at the hoof's appearance. Now look at the coronet and pastern, fetlock, flexor and extensor tendons, cannon and splint bones, hock, gaskin (upper limb), stifle, thigh, hip joint area, tuber ischii, tuber coxae, and tuber sacrale. Look for swellings or anything that looks abnormal to you.
Stand on the opposite side and assess the opposite limb similarly. Finally, (and carefully) stand behind the horse. Compare the two limbs for symmetry. Look at the conformation - the symmetry of the shapes of the hip on each side, the angles of the joints when viewed from behind. You may need to move the tail out of the way to compare the musculature for symmetry. Imagine a plumb line dropped down through the center of the hind limbs. Consider the limb conformation.
Go back to the left side of the horse. With the horse bearing weight on the limb, run your hands over the same hind limb structures, feeling for irregularities, lumps and bumps, and/or heat.
Starting at the peak of the croup (the tuber sacrale) over the hip joint and gluteal muscles. Slide your hand down over the rear of the limb, the hamstring muscles and down to the point of the hock. Feel the stifle area for swelling and heat.
Run your hands down the gaskin (upper limb) to the hock. Feel the hock for swellings and compare its appearance to the opposite side. Run your hands down the flexor tendons, feeling carefully for irregularity, swelling or enlargement.
Feel the extensor tendons, cannon and splint bones, and down to the fetlock joint. Then the pastern joint looking carefully for lumps and bumps that could indicate pastern arthritis. Finally, carefully assess the hoof wall. Feel for digital pulse and heat in the foot.
Now, raise the limb, flex the joints for range of motion and pain response. When you do this, again run your hands over the same structures, especially the joints and flexor tendons, noting any irregularities or swellings.
Now carry the limb to the rear and again feel the same lower limb structures, with the limb raised. Inspect the sole of the hoof.
Repeat this procedure on the right hind limb.
With practice you will better able to distinguish between normal and abnormal.
TIPS FOR SAFETY AND SUCCESS
Be sure to use good horsemanship when working with the hind limbs. Maintain contact with the horse and avoid surprising them with sudden contact.
When assessing the limbs of an unfamiliar horse, work with an experienced handler at the head of the horse to make this procedure easier and safer. If you do not have a helper, you will need to work on the horse tied or restrain the horse's head at the same time as you work on the limb.
Whenever handling legs and feet, always keep your back straight and your shoulders above your hips to reduce the chance for back injury.
When lifting the limbs, try to consciously keep the horse's limb under the horse, and not pulled out to the side. Horses resent having their limbs unnecessarily strained, and will resist if attention is not paid to keeping them comfortable.