FORM FOLLOWS FUNCTION
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 per- mits 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 syno- vial 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 absorb- er 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 move- ment, but involves a prominence in one bone fitting into a depres- sion 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 sepa- rately. Figure 12 shows how well they fit together.) If you have any questions or comments, or to schedule a semi- nar, contact Stephanie via email: email@example.com .
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
88 | SHOWSIGHT MAGAZINE, MAY 2021
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