The hindquarters are made up of the pelvis and overlying croup, the hind limbs and the tail. This is where the greatest part of the energy required for movement at any gait is generated, and a huge amount of stress must be absorbed and directed. Any weakness in structure here will compromise the dog's movement and should be readily apparent.

THE PELVIS
(Figure 1)
The pelvis is a complex arrangement of bones which takes the power generated by the hind legs and channels it forward into the spine. At the beginning of the pushing off stage of the stride (at any gait), the paw is positioned directly below the hip joint, and the force of the leg as it straightens is generated almost straight upwards. By the end of the stride, as the paw lifts off into the follow-through, the power is coming up at about a 45 degree angle forward, through an almost completely straightened leg (Fig 2).

The pelvis must take this energy as it comes up the leg, transmit it through the hip joint, forward along the pelvis to the joint between the sacrum and the seventh, or last, lumbar vertebra, and direct it straight forward through the spine, parallel with the ground. A correct pelvic angle allows for the smooth transmission of energy over this curve from the legs to the spine, and is about the same in all canines (and most other big predators). Off angles are seen in show bred domestic stock which haven't been physically stressed to any great degree for several generations. I like to measure it by laying a plane across the top of the pelvis rather than trying to draw lines through it. It's more objective and easier to see. By this measure, the pelvis in a dog standing four square is between 30 and 35 degrees to the horizontal, and hopefully the spine (Fig 3). The more conventional method draws a line somewhere through the middle of the ilial crest and the ischial tuberosity, and is between 20 and 25 degrees. In a show posed dog, the angle will appear somewhat steeper.

A very flat pelvis will dissipate excess force into the roof of the acetabulum (Fig 4), while an excessively steep pelvis, which is more common, will misdirect some energy upwards through the sacral joint instead of channeling it forward (Fig 5). Both conditions seem to result in a shortened stride in the rear. The flat pelvis makes a forward under reach more difficult, and the steep pelvis prevents the dogs from executing a long, smooth follow-through. The steep pelvis, which is common in many show lines, German and American, appeared because of the emphasis put on sidegait in the show ring. Many extreme side-gaiters are too long in body, though they require that length to lessen interference between very extended front and rear action. The steep pelvis gives the illusion of a shorter body. Affected American dogs show a long spine and abrupt steepness at the sacral joint (Fig 6). Affected German dogs show excess slope at the mid-back (Fig 7). You'd be surprised how many of these apparently short coupled German dogs, when you actually iron out their spines (on paper of course!) are actually rather long in body. Some even have rather flat pelvises, with the slope originating purely in the curvature of the spine. Correct pelvic slope is necessary for efficient, powerful movement, but it must originate in the right place. The slope of the pelvis normally starts at the sacral joint, not at some point of curvature further up the spine. The spine is not designed to absorb a great deal of force while curved, and this should be considered a serious fault.

The width of the pelvis is also very important, to give sufficient area of attachment to the massive muscles of the loins and thighs, and to provide bitches with a roomy birth canal. A more narrow configuration is sometimes seen in animals bred strictly for sidegait, but they lack the power and stamina of a more broadly constructed dog (Fig 8).

THE CROUP
The croup consists of the fused sacral vertebrae, or sacrum, that form the roof of the pelvis, and the first few caudal vertebrae of the tail, depending on how long the croup is (Fig 9). Its slope is usually determined by the slope of the pelvis, but not in all cases. Most dogs with a very steep pelvis will show similarly steep croup, but it is possible for a steep pelvis to carry a very high tail, and show a flat, short croup. A flat pelvis will show a flat croup, but it could be long or short depending upon the tail set. Even an ideally set pelvis can show a croup that is long or short. In fact, the length of croup really has little or no effect on gait. There is some involvement of the muscles over the croup in the distribution of power to the spine, probably as stabilizers, but length of croup doesn't affect length of stride - watch any big striding, high tailed standard poodle. The degree of slope in the pelvis is what is critical for good movement, and the requirement of a long, smoothly sloping croup and low tail set and carriage is more esthetic than practical. It is possible that the very long croup demanded of show dogs may even be problematic, as a longer croup can be achieved through softer temperament. As the mind of a dog goes, so goes its tail, and therefore, to some degree, its croup. The very strong, dominant, high drive dog that consistently carries his tail high is probably going to show some shortness of croup, at least by conformation show standards.

 

THE TAIL
For the same reasons, tail carriage has no effect on gait. Visually of course, it is much more pleasing to see a tail swept out low in a continuation of the topline than carried suddenly upward, but the actual influence of the tail on hindquarter action is nil. It is true that a long tailed dog who loses his tail may have problems adjusting its balance, but well structured dogs who are tailless from birth show no balance or gait problems. Obviously, we want a beautiful, long, bushy tail that reaches well past the hock and curves gently, without twists, kinks, curls or other interruptions, but such flaws are esthetic, not structural (Fig 10). As long as the tail hangs normally when at rest, it's basically correct. When in motion, tail carriage is an expression of the dog's state of mind. A very strong, dominant dog will carry his tail up, particularly a male in a ring full of males. Working-bred dogs often have high tails. A high set and a high carriage aren't the same thing of course, but a correctly set tail on a strong dog can fly at nearly 45 degrees from the level (Fig 11). Much higher than that, and the tail set is probably faulty. So selecting for very low tail carriage may have a negative effect on strength of temperament. Similarly, while a tail head that flows smoothly and without apparent differentiation from the croup is more esthetically pleasing than a rooty tail that seems to sprout from the croup (Fig 12), there are indications that breeding for an extremely low tail that appears clamped to the dog's rear may increase vulnerability to perianal fistula.

THE UPPER AND LOWER THIGHS
The upper and lower thigh, and their relation to each other, provide the stifle angulation required for powerful movement. Ideally, the angle at the stifle should mirror that between the scapula and the upper arm, providing the overall balance required for smoothness, stamina and strength (Fig 1). Rear angulation is a source of contention and confusion, and the one physical trait which most divides different "types" of shepherd. Like the front, it is not true that the static angle of femur to tibia/fibula must be 90 degrees, and for the same reason. When the animal is in motion its centre of gravity drops, the body is lowered slightly, and the angulation of the rear in the supporting position closes to achieve 90 degrees (Fig 2). Unlike the front, the rear is not responsible for bearing a greater proportion of the dog's weight, so a somewhat greater degree of angulation can be tolerated.

Angulation at the stifle is measured with the dog standing four square. This means, with both hind feet positioned directly under the hip joints. In a correctly angulated animal, the hocks or heels will be located on a vertical line dropped from the ischial tuberosity, the same as the horse. However, unlike the horse, the metatarsus (what we often refer to as the hock, although that term is perhaps best reserved for the joint itself) will slope forward, parallel to the femur. In other words, when four square, the hock is not vertical. This parallel configuration, with a relatively short metatarsus, is seen in virtually every canine except the long legged maned wolf. It is typical of a predator who can travel tremendous distances at a fair rate of speed, and still summon the extreme, short term speed necessary for an attack. It is not the configuration of a long legged prey animal, such as deer, antelope and horse, who can generate fantastic speed over a much longer distance. The femur should be parallel to the scapula, and the tibia/fibula should be parallel to the humerus. The long bones of the hind leg should also be equal in length to each other and to the humerus. These bones are the great levers which are the source of speed, and equal lengths produce the most propulsion with the least expenditure of energy. The much longer lower leg bones of the deer and antelope produce much greater speed and jumping ability when necessary, but they also consume a huge amount of energy when used, so these animals tend to move more sedately when not seeking to escape. Wolves and shepherds are long distance trotters who require running gear which will not consume too much energy in the search for food, or while tending sheep, and equal bone lengths provide this.

Given these requirements, one finds that the upper and lower thigh bones will be ideally angulated at about 95 degrees, the same as the shoulder. The standard suggests that the angle should approximate 120 degrees, but this must refer to the angle achieved at the stifle of the leg when drawn back in a show pose. Unfortunately, this isn't a particularly accurate way of measuring. Most dogs, once they learn to pose and are comfortable standing like this, will "settle" down in the rear, showing a lower thigh which is more level with the ground than it normally would be and increasing the angle of the hock, altering the parallel relationship with the upper thigh (Fig 13). A skilled handler can make a dog look far more angulated than it really is. Far better to measure the dog when it is standing naturally, unposed, with both hind legs together. The actual orientation of the leg bones are then far easier to see.

Bones provide the leverage, but muscles provide the power. Less than ideal angulation, more closely approximating that of the wolf, may not give the long, flowing trotting stride so prized in the show ring, but it doesn't necessarily result in a lack of power. Working-breds don't generally show a flashy sidegait at the trot, but they can have a perfectly serviceable trot and explosive power at the gallop and when jumping. Superior muscling and ligamentation can produce breathtaking speed and power even in something so oddly structured as a hyena, more than compensating for less than ideal bone structure. Angulation can also vary considerably with size. Large wolves have relatively little (Fig 14), while tiny kit foxes can show quite a lot (Fig 15). Reduced body weight makes it easier for the animal to support and move more acutely angled levers. In shepherds, a greater amount of angulation can be tolerated in smaller dogs and bitches, while large, heavily angulated males tend to be looser and rather less powerful movers. They lack the proportionately increased muscling required to support extreme angulation, relative to their weight.

Excess angulation can be cause for concern. The more acute the angulation, the more energy the dog must expend both to hold up the levers of its rear when standing, and to move them when gaiting. Typically, as the angle between upper and lower thighs becomes more acute, the tibia/fibula becomes proportionately longer than the femur, pushing the hock closer to the ground and increasing the angle between the tibia/fibula and the metatarsus, a condition known as sickle hocks. It is possible to have a more acutely angulated rear, and the long striding, spectacular sidegait it provides, without compromising overall strength, but care must be taken that equal bone lengths, powerful muscling, strong ligamentation and standard body size are maintained. Failure to keep these qualities will result in animals who, while they may display a beautiful trot, will fail to show the necessary power for a high speed gallop, impressive jumping, or quick, agile maneuvering. Again, extreme extension of front or rear at the trot is not especially desirable, as this is an endurance gait which should conserve energy. Maximum extension and energy consumption should be reserved for the gallop.

In Figure 16 I have shown several degrees of rear angulation, both posed and unposed. Dog A has insufficient rear and will show a short stride and stilted gait. Dog B shows a degree which is quite serviceable in a working dog, although it will not provide a roomy trot. Dog C has ideal angulation, enough for beautiful movement, but not so much that power is compromised. Dog D is excessively angulated, but still sound. It will show a beautiful gait at the trot, but may not be quite so powerful in jumping or galloping. This dog however, can be useful in breeding to type B dogs, with correct progeny resulting. Dog E is over-angulated and sickle hocked, and will show faulty propulsion and clumsy maneuverability.

THE HOCK AND FOOT
The hock only achieves a vertical position when the entire leg is pulled back, typically the left leg in the show pose. No matter what its position, it should be closely parallel to the femur, with the angle of the hock and the stifle being the same; about 95 degrees. Hocks which are straighter than the stifle are seen in the Chow Chow, and can dramatically shorten the stride, greatly limiting speed and jumping ability. Sickle hocks, seen on many show dogs, slope at a more acute angle than the femur, and do not snap open on follow-through (Fig 16 E). In extreme sickle hocks, the metatarsus takes an almost plantar position, flat to the ground like a kangaroo. This is a very serious fault. The hock is a relatively fragile joint with very little muscle, and its strength depends upon tight, strong ligaments and tendons. The sickle hock is always accompanied by an overly long, sloppy Achilles tendon and an inability of the hock to snap straight in follow-through. In bad cases, the hock leaves the ground in a vertical position, with almost no push off (Fig 17).Even pronounced sickle hocks aren't always obvious at a fast trot, as the leg's backward momentum will throw the joint open, giving the illusion of follow through. At the gallop however, the dog will be unable to generate real speed, and will actually prefer to trot. Because of the instability of the sickle hock joint, they are commonly associated with cow hocks, and eggbeater movement when gaiting away.

Cow hocks, where the hocks point towards each other to some degree, can be caused by two conditions, one sound, the other unsound, (or less sound). It can occur either because of a slight turning out of the entire leg from the hip, or because of twisting of the hock and stifle joints. In the first, the dog may stand slightly wide behind, with toes and stifles pointing slightly outward, and hocks slightly inward (Fig 18). This is common, and perfectly normal, as the long bones are straight in relation to each other. How comfortable do you feel standing with your feet pointing straight ahead? However, the dog moves normally, the feet turning inwards onto the centre line, pointing straight ahead and single tracking.

The second kind generally shows some abnormality in movement, as the long bones are twisted in relation to each other (Fig 19). Those that manage to single track generally show an eggbeater action, while others track with their hocks closer together than their feet. Often, the foot is correctly oriented at the beginning of the stride, and then twists outward as the leg drives back, turning the hock inward. Sometimes this can be seen when the dog is standing show posed. Cow hocks are an indication of weakness in an area that most needs great strength. At the end of the stride at the trot, the entire propulsive power of the dog is transmitted through one hock joint. At the gallop, both joints direct the force together, but the force is much greater. When jumping, even more energy is required to lift and propel the body, and the hocks bear it all.

Strong, arched, thickly padded paws are just as important in the rear as they are in the front, because of the huge amount of force being transferred from the ground through the leg (Fig 20). The rear paw even delivers some propulsion of its own. Strongly arched toes are pulled forward as the foot drives back, stretching the tendons and gathering energy which is released when the foot leaves the ground, allowing a strong, snapping follow-through. The hind paw is generally somewhat smaller than the fore paw, reducing the point of contact, concentrating power and increasing traction.

Without powerful running gear in the rear, a dog's ability to work long hours, cover ground quickly and efficiently, and navigate obstacles in its path is severely compromised. The skeletal levers must be of correct length and orientation, and the musculature and ligamentation must be very strong. Without a sound, powerful hindquarter, you might have a beautiful dog, but you don't have a working dog.