How to Draw Mammals: comparative anatomy of the legs

At first glance, mammal legs seem hopelessly complex and variable with joints bending in confusing directions. However, the differences are restricted to how the animal holds its foot. If you master three basic foot postures and you will understand how to draw mammal legs.

The most familiar stance is walking on the entire sole of the foot as we humans do. This is called plantigrade and the plantar surface (sole) of the foot is in contact with the ground. Humans, bears and raccoons are good examples of plantigrade animals.
Other animals walk on the pads of their toes and the ball of the foot with the heel up in the air. This is called digitigrade as the animal walks on its digits. Dogs and cats are familiar examples. Many people are confused at the dog’s backward pointing knee but a closer look reveals that this is a normal heel which is permanently off the ground.
The third group walks up on their toenails or the hoof. These animals are refered to as unguligrade as they walk on the unguis of the nail. Some ungulates have one hoof (horses and zebra) while other have hooves that are cloven in two (deer, cows, pigs, goats, sheep). Click to enlarge the images and captions below.

Bones of the front limb of a bear, lion, and deer (left to right) showing how variation in the foot position changes the shape of the leg. Note how far the wrist is off the ground in the deer. The “hand” is the region shaded in orange.

Bones of the hind limb of a bear, lion, and deer (left to right) showing how variation in the foot position changes the shape of the leg. Note how far the heel is off the ground in the deer. The “foot” is the region shaded in orange.

When you look at a mammal in profile, the elbow and knee may be flush with the level of the belly so that you do not see these joints in the space below the body. This causes a lot of confusion because people assume that the joint at the edge of the body will be the shoulder and hip. In some animals you will see the knee quite far below the line of the belly such as in shorter haired dogs or the cheetah so this is a good detail to check.

Another useful thing to note is the height of the wrist from the ground. The wrist of the plantigrade mammal is at ground level. That of a digitigrade mammal such as a cat or dog is a little off the ground. The wrist of a ungulate such as a deer is half way between the elbow and the hoof! Since a deer’s elbow is held up against the body, you will see the wrist half way down the exposed portion of the front leg. Click on one of the images below to enlarge and read details and key points to observe.

Bear skeleton showing plantigrade stance. As the animal walks, it will roll onto the pad of the foot but when bearing full weight, the full sole of the foot is on the ground. Note the elbow and knee at the level of the belly.

Mountain Lion skeleton showing digitigrade stance. Note the elbow and knee flush with the level of the belly and how close the wrist is to the ground.