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Arthrology: The study of the joints. |
| Classification of joints according to movement:
Synarthrotic joints (synarthroses) - non-movable joints. Most fibrous joints are of this type. They are composted of dense fibrous tissue between the bones. Example: the sutures. Other types of fibrous joints are called syndesmoses. They have a short ligament between the bones. Example: tibia-fibula. Amphiarthrotic joints (amphiarthroses) - semi-movable joints, mostly cartilaginous. Examples: intervertebral disks, symphysis pubis. Diarthrotic joints (diarthroses) - movable joints. Mostly the synovial joints. |
| Classification of joints according to structure:
Fibrous joints - structure of fibrous connective tissue. Types: the sutures, syndesmoses (e.g. the tibia-fibula, clavicle-scapula, etc.). (See Figure 8.1) Cartilaginous joints - structure of hyaline or fibrocartilage. (See Figure 8.2). Examples: synchondroses (e.g. first rib-sternum), symphyses (e.g. intervertebral disks, symphysis pubis). Synovial joints - structure includes a synovial capsule for lubrication. (See Figure 8.3). Important structures associated with synovial joints: Articular cartilage - hyaline cartilage protects ends of bones. Extracapsular ligaments - lying outside the joint capsule, these ligaments hold bones in position while permitting movement. Intracapsular ligaments - lying inside the joint capsule, these ligaments restrict degree and types of movement. Menisci - cartilage pads within the joint which cushion and accommodate the shapes of bones. Friction Reducing Structures: Bursae and Tendon Sheaths (See Figure 8.4) These are synovial membranes which lie between ligaments (bursae) or surround ligaments (tendon sheaths) to lubricate their movement. Inflammation causes bursitis which, while it doesn't physically restrict the movement of the joint, makes it very painful. |
| Types of synovial joints: (See Figure
8.7)
uniaxial joints - allow movement in one axis. hinge joint - elbow, knee - flexion, extension; pivot joints - radius-capitulum of humerus, atlas-axis - rotation biaxial joints - allow movement in two axes. E.g. condyloid joints, saddle joint - carpals-metacarpals - flexion, extension, adduction, abduction, circumduction. multiaxial joints - hip, shoulder - all movements. |
| Movements at synovial joints:
Movement in an anteroposterior direction from anatomical position: flexion - decrease of angle between parts; e.g. bending elbow or knee, lowering head to chest extension - increasing the angle between parts; e.g. straightening elbow or knee, raising head from chest. Movement in a sideways direction from anatomical position: adduction - lateral movement together or toward midline; e.g. bringing arm to side. abduction - lateral movement away from midline or apart; e.g. raising arm away from side. circumduction- a succession of four movements resulting in the distal end of a bone inscribing a circle. Other movements: rotation - a bone or part turning on an axis; e.g. rotation of radius as in supination and pronation; turning the head. supination - moving the palm up or forward; pronation- moving palm down or backward inversion - moving the sole of the foot inward. Also could be described as foot adduction. Incorrectly called "supination", a term reserved for the hand. eversion - moving the sole of the foot outward. Also could be described as abduction. Incorrectly called "pronation", a term reserved for the hand. elevation - raising a part, e.g. as in shrugging the shoulder. depression - lowering a part. protraction - moving a part forward; retraction- moving a part backward |
| The major joints: See [
Radiographic Images]
The shoulder (See Figure 8.8) - The shoulder joint has a very shallow socket (the glenoid fossa) and therefore has poor skeletal support. For that reason its muscular support is critical and is a result of the muscles known as the rotator cuff. These muscles are the subscapularis, supraspinatus, infraspinatus, and teres minor. The elbow (See Figure 8.10) - elbows have medial and lateral collateral ligaments like the knee, and in addition have an annular ligament which acts as a collar around the head of the radius to permit its rotation. The hip (See Figure 8.9) - The acetabular fossa is much deeper than that of the elbow and supports the hip much more. Even normal walking puts a force several times the body weight on the hip. Ligaments also hold the femur in position, especially the ligamentum teres, or round ligament. The
knee
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| Joint disorders - arthritis is the name given to inflammation of a joint. There are three types:
osteoarthritis - this is the most common type of arthritis affecting 90% of all arthritis sufferers. It is associated with deterioration of the articular cartilage which then leads to the formation of calcifications or bone spurs. These bone spurs irritate the articular capsule and cause pain. Little, if any, actual inflammation occurs. The articular cartilage deteriorates because of age, stress, and injury. Rheumatoid arthritis [See also] This is the most severely debilitating form of arthritis, but affects less than 10% of arthritis sufferers. It is considered an autoimmune disease and begins with immune system cells releasing chemicals which attack the joint tissues. Severe inflammation results in great pain. The inflamed tissues become infused with fibrous tissue causing great stiffness and this fibrous tissue may eventually ossify to form bony connections which render the joints immobilized and visibly misshapen. Pain relieving drugs and surgery, even joint replacement, are the treatments. Gouty arthritis - the gout is a genetic disorder of the ability to metabolize uric acid. Uric acid is a product of the breakdown of certain nucleic acids. Most people convert it to urea for excretion. In these individuals uric acid crystals build up in the soft joint tissues and causes their inflammation and destruction. It is especially likely to affect the big toe. Anti-inflammatory drugs and dietary restrictions are the treatment. |
| Joint injuries:
A sprain involves twisting of the joint, often with accompanying stretching and tearing of ligaments. These ligaments are slow to heal because of their lack of vascularization; support or immobilization is the treatment. With very severe sprains involving intracapsular ligaments surgery may be performed to reattach the ligaments or replace them with a portion of a ligament from some other location. A strain usually involves a pulling of a muscle tendon and other connective tissues in muscles, not the joint tissues. Small strains are normal and the inflammation produced causes the soreness you may experience after strenuous exercise. Major pulls result from more severe stretching and take longer to heal. A luxation is a dislocation in which a bone such as the humerus or femur pulls away from its position in the socket of the joint. A complete luxation may stretch or tear accompanying ligaments to the point they will not return to normal. Partial dislocation or subluxation is more common and the bone can usually be returned manually to its normal position. A separation occurs when the fibrous tissue in a syndesmosis stretches or tears. The most common is a shoulder separation in which the clavicle pulls away from its attachment to the acromion process of the scapula. |
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