Freely movable. Most joints in the body arefreely movable joints. The joint consists of the jointcapsule, articular cartilage, synovial membrane,and synovial (joint) cavity (fig. 1-26). There are sixclassifications of freely movable joints: ball-in-socket,condyloid, gliding, hinge, pivot, and saddle joints(fig. 1-27). These joints have much more complexstructures than the immovable and slightly movablejoints. The ends of the bones in this type of joint arecovered with a smooth layer of cartilage. The wholejoint is enclosed in a watertight sac or membranecontaining a small amount of lubricating fluid. Thislubrication enables the joint to work with little friction.Ligaments (cords or sheets of connective tissue) reachacross the joints from one bone to another and keep thebone stable. When ligaments are torn, we call the injurya sprain; when bones are out of place, we refer to this asa dislocation; and when bones are chipped or broken,the injury is called a fracture.TYPES OF JOINT MOVEMENTSJoint movements are generally divided into fourtypes: gliding, angular, rotation, and circumduction.GlidingGliding is the simplest type of motion. It is onesurface moving over another without any rotary orangular motion. This motion exists between twoadjacent surfaces.AngularAngular motion decreases or increases the anglebetween two adjoining bones. The more commontypes of angular motion are as follows:Flexion—bending the arm or leg.Extension—straightening or unbending, as instraightening the forearm, leg, or fingers.Abduction—moving an extremity away fromthe body.Adduction—bringing an extremity toward thebody.RotationRotation is a movement in which the bone movesaround a central point without being displaced, such asturning the head from side to side.1-16SYNOVIALMEMBRANESYNOVIAL(JOINT)CAVITYJOINTCAPSULEARTICULARCARTILAGEFREELY MOVABLEJOINTSYMPHYSISPUBISCORONALSUTUREINTERNASALSUTUREFIBROUSSUTUREIMMOVABLEJOINTSLIGHTLY MOVABLEJOINTHM3F0126Figure 1-26.—Example of immovable, slightly movable, and freely movable joints.
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