Joint Types and Movements

Overview

This lecture covers joints (articulations), their classification, structural features, and the various types of joint movements important for skeletal mobility.

Functions of Joints

• Joints (articulations) connect bones and allow for skeletal mobility.
• Main functions: hold the skeleton together and allow movement.

Joint Classification

• Joints are classified structurally as fibrous, cartilaginous, or synovial.

Fibrous Joints

• Two or more bones joined by fibrous tissue, with no joint cavity.
• Sutures: immovable joints joining skull bones.
• Syndesmosis: bones united by ligaments or sheets of fibrous tissue (e.g., between radius/ulna, tibia/fibula).
• Gomphosis: cone-shaped process in a bony socket, e.g., teeth in mandible/maxilla.

Cartilaginous Joints

• Bones joined by cartilage, allowing slight movement.
• Synchondrosis: bones united by hyaline cartilage (e.g., sternum and ribs, epiphyseal plate).
• Symphysis: bones connected by fibrocartilage (e.g., intervertebral discs, pubic symphysis).

Synovial Joints

• Freely movable joints with a joint cavity filled with synovial fluid.
• Features: articular cartilage, joint cavity, joint capsule (outer ligament layer, inner synovial membrane).
• Synovial fluid reduces friction and is "slicker than ice".
• May include reinforcing ligaments, menisci (shock-absorbing pads), and bursae (fluid-filled sacs for shock absorption).

Types of Synovial Joints

• Ball-and-socket: movement in all planes (shoulder, hip).
• Ellipsoid (Condyloid): oval surfaces (atlas and occipital condyles).
• Plane: flat surfaces gliding (carpals, tarsals, vertebrae).
• Hinge: flexion and extension (elbows, knees).
• Pivot: rotation around axis (radius/ulna, atlas/axis).
• Saddle: both bones saddle-shaped (base of thumb).

Types of Joint Movements

• Flexion: decreasing joint angle.
• Extension: increasing joint angle.
• Hyperextension: excessive extension beyond normal range.
• Dorsiflexion: foot moves upward.
• Plantar flexion: foot moves downward.
• Abduction: movement away from midline.
• Adduction: movement toward midline.
• Rotation: part moves around an axis.
• Circumduction: movement in a circular path.
• Pronation: palm down.
• Supination: palm up.
• Eversion: sole of foot faces laterally.
• Inversion: sole of foot faces medially.
• Elevation: raising a body part.
• Depression: lowering a body part.
• Protraction: moving part forward.
• Retraction: moving part backward.
• Lateral/Medial Excursion: jaw moves side to side/back to center.
• Opposition: thumb moves toward fingers.
• Reposition: thumb returns to neutral position.

Key Terms & Definitions

• Articulation — a joint; where two bones meet.
• Suture — immovable fibrous joint in the skull.
• Syndesmosis — fibrous joint with bones connected by a ligament.
• Gomphosis — joint binding a tooth to its socket.
• Synchondrosis — cartilaginous joint with hyaline cartilage.
• Symphysis — cartilaginous joint with fibrocartilage.
• Synovial Joint — freely movable joint with a cavity containing synovial fluid.
• Meniscus — fibrocartilage pad for shock absorption.
• Bursa — synovial fluid-filled sac reducing friction.

Action Items / Next Steps

• Review diagrams of each joint type.
• Practice identifying joint types and movements on your own body.
• Read the textbook section on joint injuries and diseases for next class.