The running and jumping gear of our little Tibetan is of utmost importance. Well protected with hair, his legs must be short, strong and well muscled. The Apso does not have the straight front construction or stiff movement of a terrier. He needs the resilience and elasticity of a cat to cope with mountain terrain on his short legs. The pasterns and hocks are well let down. This is a necessity for an animal which must run and jump in snowy conditions. All of us have watched our Apsos on a snowy day scampering like rabbits across the top of the snow. The straight pastern and "up on toes" posture of a terrier, would not allow the Apso to run on top of the snow. Rather he tends to have sloping pasterns which turn out slightly and he stands on his pads as well as his toes. Not only are the tops of his feet covered with hair, but the soles of the feet as well. Thick masses of hair grow from between his pads, giving additional protection against cold and sharp stones, and a sort of snowshoe to keep him on top of deep snow.

Since the Apso's extremities are somewhat shortened, we cannot expect terrier type straight front legs. In fact the (almost pigeontoed) front we find on some terriers is a manmade aberration. All efficient four legged (and two legged) creatures tend to turn their feet out slightly. If you don't believe this, just watch your own feet as you walk. Just as we do not expect a Fox Terrier front, do not want a Pekinese front either. A certain amount of turning at the pastern of a Lhasa is acceptable, but no more than is necessary for an efficient, elastic, single-tracking gait.

The front limb of the dog behaves in exactly the same fashion as the human arm.  Consider the diagram A. The unshaded arm is analogous to the standing position of a fox terrier - perfectly straight at the wrist. This is the correct position for a narrow terrier, because these dogs do not bring their feet under the body, but tend to move the front legs - pendulum fashion - straight ahead. (they avoid a roll by having very rigidly coupled, narrow, short bodies.)

The Lhasa, however is a very flexible, longer bodied dog, which avoids a rolling gait by "single-tracking" - bringing the feet toward the midline. What happens when the "straight pasterned" foot is brought to the midline. Diagram "A" shows that the foot no longer points in the direction of travel. but now "toes-in". During the weight-bearing portion of the stride, this puts torque on the wrist bones (pastern), and produces an abnormal gait.

Diagram "B" shows the midline foot position, with the wrist (pastern) correctly angled for the weight bearing portion of the stride.  When the foot is in the standing position (the foot directly beneath the elbow) it toes out slightly.

Thus you can see that the single tracker should not have the absolutely straight pastern of the Fox Terrier. Since the Lhasa is wider, longer bodied, and more flexibly coupled than a fox terrier, the mechanics of his front movement are significantly different. The Lhasa with a terrier front will either move wide, and roll, or it will toe in and appear to be weaving in the front. The latter problem being the more serious, because it causes abnormal stresses on the joints.