Joint Types and Movements Overview

Overview

This session reviewed joint types, major ligaments, and movements in the human body, focusing on the pelvis, vertebral column, and related anatomical terminology and concepts.

Types of Joints

• Sutures are immovable joints found in the skull.
• Syndesmosis joints are connected by interosseous membranes (e.g., between radius/ulna or tibia/fibula).
• Gomphosis joints anchor teeth in the jaw.
• Synchondrosis (primary cartilaginous) joints include growth plates and first rib to sternum.
• Symphysis (secondary cartilaginous) joints include the pubic symphysis.
• Synovial joints (plane, ball and socket, hinge, etc.) allow for varying levels of movement.

Pelvic and Vertebral Joints

• The sacroiliac (SI) joint connects the sacrum and the ilium of the pelvis.
• The acetabulofemoral (hip) joint is a ball-and-socket synovial joint.
• Zygapophyseal (Z) joints are synovial plane joints found between vertebrae.

Ligaments: Structure and Function

• Ligaments are classified as extrinsic (outside the joint) or intrinsic (inside the joint capsule).
• SI joint ligaments include anterior sacroiliac (intrinsic) and long posterior sacroiliac (resist certain pelvic movements).
• Ligaments attach to bones but do not have classic origins/insertions like muscles.
• Ligaments limit motion, provide tension, and stabilize joints.

Movement Rules & Biomechanics

• Convex on concave: roll and glide in opposite directions.
• Concave on convex: roll and glide in the same direction.
• Roll of a bone is always in the same direction as movement.
• Example: flexion/extension at knee or elbow follows these rules.
• Range of motion (ROM) is limited by ligament length and tension.

Nervous System Basics

• Afferent (sensory) fibers carry signals to the CNS; efferent (motor) fibers carry signals away.
• Bundle of axons in CNS: tract; in PNS: nerve.
• Sensory input is from organs/body to CNS; motor output is from CNS to the body.

Anatomical Planes & Terms

• Oblique plane cuts at an angle.
• Sagittal plane divides body into left and right; main movements are flexion/extension.
• Concave: depressed surface (open palm); convex: raised surface (closed fist).

Rib and Vertebrae Relationships

• Ribs are numbered according to the vertebra below them.
• Transverse process of a vertebra articulates with the rib of the same level.

Key Terms & Definitions

• Suture — immovable joint in the skull.
• Syndesmosis — joint with bones connected by a ligament or membrane.
• Synchondrosis — primary cartilaginous joint, e.g., growth plate.
• Symphysis — secondary cartilaginous joint, e.g., pubic symphysis.
• Synovial Joint — freely movable joint with a joint capsule.
• Intrinsic Ligament — located inside the joint capsule.
• Extrinsic Ligament — located outside the joint capsule.
• Convex/Concave Rule — direction of roll and glide depends on moving surface shape.
• Zygapophyseal Joint — plane synovial joint between vertebrae.
• Afferent/Efferent — sensory input to CNS/motor output from CNS.

Action Items / Next Steps

• Review classification and examples of joints and their ligaments.
• Practice convex/concave rules using joint movements.
• Memorize key terms and ligament functions.
• Study anatomical relationships for ribs and vertebrae.
• Be prepared to identify joint types and anatomical features without images on exams.