CHAPTER 2 Structure and Function of Joints


connective tissues of periarticular structures are com- posed of fi brous proteins, cells, and a matrix. The arrange- ment and proportion of these components vary and relate directly to the function of each joint structure. Ligaments and joint capsules provide stability to joints and resist forces that could lead to joint malalignment. Tendons transfer muscle forces to bones to produce either joint stability or movement. Articular cartilage and fi brocarti- lage counter weight-bearing and compression forces to joints. Bones provide the rigid shape of the body, act as levers for movement, provide protection for organs, store calcium, and produce cells. Each of these joint structures has a different capacity for healing if injured, depending on its individual blood supply and the amount of cells available for regeneration. Joints can be classifi ed in one of two ways, depending on whether the approach is from an anatomical (structural) point of view or a kinesthetic (functional) one.


Understanding whether a joint is uniaxial, biaxial, tri- axial, or planar provides insight in determining the move- ments necessary to restore a joint to its optimal function during rehabilitation. Joint movement is observed and described in terms of osteokinematic and arthrokinema- tic motion. Osteokinematic motion is the motion of the bone lever as it moves in the cardinal planes. Arthro- kinematic movement is the motion that occurs between two joint surfaces in terms of a roll, glide, or spin. For optimal movement of a joint through full anatomical range of motion, arthrokinematic motion between joint surfaces must occur.


DISCUSSION QUESTIONS


1. Which type of collagen is found in ligaments and tendons, and what purpose does the collagen serve in their function?


2. What role do glycosaminoglycans play in the ground substance found in periarticular structures?


3. Describe the composition and function of joint capsules, tendons, ligaments, bursae, fibrocartilage, and articular cartilage.


4. What role does synovial fluid play in the function and health of joints?


5. What purpose do the sensory receptors located in joint capsules and ligaments serve in the function of joints? If these sensory receptors were damaged during a ligament sprain, how might that affect a person’s ability to walk on unlevel nonlevel unlevel surfaces?


6. Give an example of each of the following types of joints: syndesmosis, suture, gomphosis, symphysis, synchondrosis, and synovial.


7. Describe the difference between uniaxial, biaxial, triaxial, and nonaxial joints, and give an example of each type.


8. Analyze the following activities in terms of joints involved, their degrees of freedom, and whether each joint provides mobility or stability during the movement: brushing teeth, kicking a ball, donning a shirt, and jumping. Hint: Consider the role of the trunk during these activities.


9. What type of restrictions are likely to be involved with hard, soft, firm, and empty end-feels?


Kinesiology in Action Case Study M


s. Smith fell on her outstretched hand and sustained a Colles fracture of the distal radius


2 cm proximal to the radiocarpal joint. In addition to the fracture, the interosseous membrane between the distal radioulnar joint was disrupted. The frac- ture was treated surgically with an open reduction internal fixation of the radius, and her arm was immobilized in a splint for 4 weeks. Ms. Smith was instructed not to bear weight on the hand, wrist, or arm during this period of healing. 1. What type of joint is the radiocarpal joint?


2. What changes are likely to happen to the ligaments and joint capsules around the wrist and forearm during this period of immobilization?


3. Will Ms. Smith likely be able to move her wrist through full flexion and extension when the splint is removed? Why or why not?


10. Discuss the osteokinematic and arthrokinematic motion that occurs at the knee joint as the joint moves from 90° of flexion into full knee extension.


11. How much joint play can be expected in a joint in its close-packed position?


12. Describe the arthrokinematic motions of roll, glide, and spin.


13. Define the concave-convex pattern of arthrokinematic motion.


BIBLIOGRAPHY


Buckwalter JA. Articular cartilage: injuries and potential for healing. J Orthop Sports Phys Ther. 1998;28:192–202. Cosby NL, Koroch M, Grindstaff TL, Parente W, Hertel J. Immedi- ate effects of anterior to posterior talocrural joint mobilizations following acute lateral ankle sprain. J Man Manip Ther. 2011; 19:76–83.


Haemer JM, Carter DR, Giori NJ. The low permeability of health meniscus and labrum limit articular cartilage consolidation and maintain fl uid load support in the knee and hip. J Biomech. 2012;45:1450.


Levangie PK, Norkin CC. Joint Structure and Function: A Comprehensive Analysis. 5th ed. Philadelphia, PA: FA Davis; 2011.


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