Dogs' legs are comprised of bones, muscles, ligaments and tendons. The anatomy of a dog's hind leg and foreleg differs just as a human arm and leg differ, according to For Dummies.
Directly below the shoulder of the foreleg is the humerus bone, which ends at the elbow, the first joint located just below the chest on the back of the foreleg. The forearm, comprised of the ulna and radius, spans from the elbow to the wrist, the lower joint on the foreleg. Both forelegs and hind legs have a paw at the end. Bones called pasterns are in their feet. The paw includes five paw pads and nails, which are attached to the last bone of the toes. For Dummies explains that dogs usually have dewclaws, which are useless appendages that are vestiges of thumbs.
The hind leg forms a joint at the pelvic bone. The upper thigh, or femur, is the part of the leg above the knee on the hind leg. The stifle, or knee, is the joint on the front of the hind leg. The lower thigh, made up of the tibia and the fibula, is the part of the hind leg beneath the knee to the hock, which is the oddly shaped joint that makes a sharp angle at the back of the dog’s legs, as explained by For Dummies.
The Veterinary Expert explains how the quadriceps muscle towards the front of the thigh is responsible for extending the stifle joint. The patella, or kneecap, is a bone is attached to the underside of the tendon at the end of the quadriceps muscle.