Form Follows Function | Joints Where Bones Meet!

First, let us do a brief review of some of the basics.

ANGULATION refers to the angles created by bones meeting at various joints (articulations), especially at the shoulder (Fig. 1A) and pelvic areas (Fig. 1B) and the stifle (Fig. 1C), hock (Fig. 1D), pastern (Fig. 1E) and at the elbow (Fig. 1F).

BONE comprises the structure of the skeletal system and provides lever arms for locomotion. Bone also plays important roles in maintaining mineral homeostasis (the balance of minerals, especially calcium and phosphorus). The bones must supply sufficient area for the attachment of the muscles. Smooth muscles account for one-third to one-half of the total body weight.

Figure 2. Canine skull with some sutures accentuated.

MUSCLES move the bones and dictate where they will go and where they will stop. The skeleton is simply bone, and has no means of creating motion by itself. Although we are concentrating on the inner structure of the skeleton and its articulations and relationship, without muscles there is no movement. The musculature of the dog is a complicated subject, too lengthy for us to approach here. We are simply going to try to understand the structural limitations imposed by the composition of the juncture of the various bones, and leave the study of the muscles of the dog up to the individual student.

Figure 3. Fibrous joint sutures in skull showing connective tissue.
Figure 4. Intervertebral Disc
Figure 4a. Placement of Invertebral Discs in Spinal Column and Sternum

TENDONS connect muscle to bone and are part of the muscle structure.

LIGAMENTS are NOT part of the muscle structure. They are tough, fibrous bands developed at joints to connect bones to other bones. Other ligaments form slings to hold tendons at the shoulder, wrist, and ankle joints.


There are “joints” (as in popular “joints” where people meet up), and then there are the joints formed within the body. Basically, a joint or articulation is a point where two or more bones meet and are united by fibrous, elastic or cartilaginous tissue or a combination of these tissues. There are three main types of joints: Fibrous (immovable); Cartilaginous (partially moveable); and Synovial (freely moveable).

Fibrous Joints are those that are stationery, such as the joints in the skull, which allow little to no movement. The bones are held together tightly by tough, fibrous, connective tissue. (See Figure 2.)

The canine skull is actually made up of over 40 different bones, all tightly held together by this fibrous tissue. These various fibrous joints, also called “sutures” (see Figure 3A) serve to allow enough movement to absorb the shock of a blow as well as allow for growth at the edges of the bone. The fibrous joints range from those where a slight degree of compressibility is advantageous to those where a more extreme stability is desirable. A fibrous joint may have a considerable amount of intervening connective tissue.
(See Figure 3.)

Cartilaginous Joints allow some movement as compared to a fibrous joint, but less movement than a synovial joint. Cartilaginous joints are formed when two or more bones are joined together entirely by cartilage. The joints formed between each vertebra in the spine are cartilaginous joints, allowing a smooth, frictionless movement of the spine. (See Figure 4.) The intervertebral disc is composed of fibrocartilage, which joins two vertebrae together. The center of the disc consists of a gel-like material. Another example of cartilaginous joints are the joints where the ribs meet the sternum.

Synovial Joints are, by far, the most common classification of a joint within the canine body.

They are highly moveable and all have a synovial capsule (collagenous structure) surrounding the entire joint, a synovial membrane (the inner layer of the capsule) that secretes synovial fluid (a lubricating liquid), and cartilage known as hyaline cartilage that pads the ends of the articulating bones (fibrous tissue enclosing a synovial cavity). The joints are lubricated for smooth action by synovial fluid and are stabilized by tendons and ligaments. The joints are the hinges of the body. A well-formed joint allows bones to act as levers; the bones move at angles to each other to produce movement. Internally, they have cushion-like padding called cartilage. Externally, they are held together by flexible ligaments.

There are six types of synovial joints, which are classified by the shape of the joint and the movement available.

The dog’s body has three basic types of joints that we are going to discuss:

  • BALL AND SOCKET such as the hip and shoulder joints.
  • HINGED such as the knees and elbows, which move in one plane (like a door).
  • GLIDING or PLANE such as the wrists and ankles.
  • CONDYLAR such as the stifle (knee) that resembles a hinge joint in movement, but differs in structure. (For the sake of simplicity, we will consider these to be hinged joints.)

left to right: Figure 5. Upper Arm/Shoulder Blade Joint; Figure 6. Pelvis/Femur Hip Joint; Figure 7. Elbow Joint; Figure 8. Stifle Joint

A BALL AND SOCKET JOINT moves in two directions with rotational capabilities. It is formed by a convex hemispherical head, which fits into a cavity. (See Figures 5 & 6 and Figure 9 for an x-ray of a hip joint.)

A HINGED JOINT moves on one axis (like a door). It permits flexion and extension with a limited degree of rotation. The most moveable surface of a hinged joint is usually concave. (See
Figures 7 & 8.)

In the GLIDING or PLANE JOINT, the articular surfaces are nearly flat. The bones that make up the joint can glide or rotate. The pastern joint (carpus joint) of the dog is located approximately in the same position as the human wrist. (But it is NOT a wrist!) The carpal bones in this joint form two rows. (See Figure 9.) It is a synovial joint, comprised of a common outer fibrous capsule and three inner synovial pouches, one for each joint. Numerous ligaments add to the stability of the joint and ensure that movement is largely limited to a gliding motion and a very small amount of rotation.
(See Figure 9A.) The pastern serves as the dog’s main shock absorber and allows for flexibility in movement. Let me repeat myself: Pasterns absorb the impact of every step ever taken by your dog. (See Figure 9.)

A CONDYLAR JOINT resembles a hinged joint in movement, but involves a prominence in one bone fitting into a depression in the articulating bone. A good example is the stifle. (See Figures 10, 10A & 10B.) It looks much like a knuckle, and results in two articular surfaces, usually included in one articular capsule. These knuckle-shaped condyles vary in distance from one another, allowing uniaxial movement with limited rotation.

After my dogs had their way with a cow bone, I saved it to photograph as it really does demonstrate how a condyle joint fits together. (Figure 11 shows the leg bone and the carpal bones separately. Figure 12 shows how well they fit together.)

If you have any questions or comments, or to schedule a seminar, contact Stephanie via email:

left to right: Figure 9. Pastern (Carpus) Joint; Figure 9A. Pastern (Carpus) Joint; Figure 10. Stifle Condyles

left to right: Figure 10A. Hip Ball and Socket Joint and Condyles on Femur (Young German Shepherd Dog); Figure 10B. Condyles on Femur; Figure 11. Separated Condyle Joint; Figure 12. Condyle Joint Articulation

  • My involvement with the world of showing dogs began in 1969 with the purchase of my first show dog, a German Shepherd Dog. In the mid-seventies I began breeding and showing Pembroke Welsh Corgis under the Jimanie prefix and have finished a championship on a Pembroke Welsh Corgi on the average of one a year for the last 45+ years - almost all were breeder/owner handled to their titles. In 2010, I formed a loose partnership with two long-time friends, Denise Scott and Linda Stoddard, and we now breed and show under the Trifecta prefix. I am a breeder/owner/handler and still breed and show. Over the years I have owned and shown dogs mostly from the Herding and Sporting Groups plus a few toy breeds. I started out showing dogs from the Herding Group, but as a hunter, I always had a “bird dog” and thus also showed Brittanys, Pointers, Golden Retrievers and Irish Setters over the years. I have finished dogs in several other breeds from the Sporting and Toy groups. I started my judging career in 1988 with AKC approval to judge German Shepherds, Cardigan and Pembroke Welsh Corgis. I judge the Herding, Sporting and Toy groups and several of the Non-Sporting breeds, as well. I have been fortunate enough to have judged dogs all over the US and Canada and also in Finland, Norway, Sweden, Jamaica, New Zealand, Australia, Ireland, China, the Philippines, Mexico and the United Kingdom. In 2011, I was accorded the supreme honor of being asked to judge the Welsh Corgi League show in the UK and in previous years both the Cardigan and Pembroke Nationals in the US. I have also had the honor of having judged many National and Regional Specialties for breeds I did not breed, own or show from the sporting, herding and toy groups throughout the years, an assignment I always enjoy! Some of the highlights of my judging career have been judging at Westminster Kennel Club in 2006, doing the Herding Group at the Rose City Classic in Portland which was shown on Animal Planet and the national specialties for Clumber Spaniels, Field Spaniels, Australian Shepherds, Miniature American Shepherd, Bouviers (Canada) and the Top Twenty competition for the Golden Retriever Club of America as well as both of the Corgi national specialties in the US and Pembrokes in Canada and the Welsh Corgi League show mentioned above. I make my living as an artist, mostly through the design of counted cross-stitch and needlepoint but also through paintings and sculpture as well as jewelry. I have recently begun authoring and producing DVDs on the canine, mostly dealing with structure and movement. Last, but certainly not least, I’ve been married to Jim Hedgepath since 1972 and am the mother of two and the grandmother of four. Thank you for the honor of being invited to judge your dogs.

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