Joint Structure

Classification of Joints Fibrous (synarthroses): lacks a joint cavity and the articulating bones are held very closely together by fibrous connective tissue; they permit little or no movement sutures syndesmoses gomphoses

Sutures found between the bones of the skull and are united by a thin layer of dense fibrous connective tissue

Syndesmoses fibrous connective tissue forms an interosseous membrane or ligament (distal articulation of the tibia and fibula, shafts of radius and ulna)

Gomphoses cone-shaped peg fits into a socket (teeth)

Classification of Joints Cartilaginous (amphiarthroses): lacks a joint cavity and the articulating bones are tightly connected by cartilage synchrondrosis symphyses

Synchrondrosis connecting material is hyaline cartilage (epiphyseal plate)

Symphyses connecting material is a broad, flat disc of fibrocartilage (pubic symphysis; bodies of vertebrae)

Classification of Joints Synovial (diarthroses): joint cavity (space between the articulating bones) is present; freely movable. Gliding Hinge Pivot Ellipsoidal Saddle Ball and socket

Synovial Joints are freely movable

Gliding side-to-side and back-and-forth movements (biaxial); articulating surfaces are usually flat (intercarpal, intertarsal, sternum and clavicle)

Synovial Joints

Hinge motions are flexion/extension (monoaxial); convex surface of one bone fits into the concave surface of another (elbow, knee)

Synovial Joints

Pivot rotational movement (monoaxial); rounded, pointed, or concave surface fits into a ring formed partly by bone and partly by a ligament (atlas and axis)

Synovial Joints

Ellipsoidal side-to-side and back-and-forth movements (biaxial); oval shaped condyle fits into an elliptical cavity (wrist)

Synovial Joints

Saddle side-to-side and back-and-forth movements (biaxial); articular surfaces concave in one direction and convex in opposite direction (CMC of thumb)

Synovial Joints

Ball and socket movement in 3 planes (triaxial); ball like surface fits into a cuplike depression (shoulder and hip)

Synovial Joints

Components of Synovial Joints articular cartilage: covers surfaces of articulating bones but does not bind them together articular capsule: surrounds the articular surfaces and encloses the joint cavity outer layer (fibrous capsule): attached to the periosteum of articulating bones at a variable distance from the edge of the articulating cartilage inner layer (synovial membrane): secretes synovial fluid which lubricates the joint and provides nourishment for the articular cartilage

Components of Synovial Joints joint (synovial) cavity: enclosed space that surrounds the 2 articulating surfaces; contains the slippery lubricating fluid called synovial fluid ligaments: thickened collagenous bands connecting bone to bone extracapsular ligaments are outside of the articular capsule (MCL, LCL) intracapsular ligaments directly attach the 2 articulating surfaces (ACL, PCL)

Components of Synovial Joints articular discs (menisci): pads of fibrocartilage that lie between the articular surfaces of the bones; help maintain the stability of a joint and direct the flow of synovial fluid to areas of greatest friction; not all synovial joints have them

Components of Synovial Joints bursae: saclike structures that contain synovial fluid to help reduce friction between: skin and bone tendons and bones muscles and bones ligaments and bones