A dog's rear leg skeleton is made up of the tibia (the larger of the two bones in the rear leg) and fibula (the smaller of the two bones). These two bones join together just below the knee, forming a ball-and-socket joint. The femur, or thigh bone, is located above the tibia and fibula.
The largest muscles in a dog's rear leg are found at the back of the leg, near the ankle. These include the hamstrings, calves, and quadriceps (front thigh muscle). Other muscles in a dog's rear leg include muscles that control motion (such as those that rotate joints), hold objects steady, and help you walk.