CHAPTER 7 Articulations “Joints” Joints: Structural and functional classification Structure of a typical synovial joint Types of synovial joints Terms for descriptions of movements

JOINTS Defined: any place where two bones come together General Function of Joints: - Hold the skeleton together - Allow for increased mobility and flexibility of skeleton

CLASSIFICATION OF JOINTS Joints can be classified based on: -function (what kind of movement they allow) -structure (what material is found in the joint and if is there a joint cavity present). You are required to know each of these categories.

Functional classification Synarthroses – joints that have NO movement. Examples: sutures of the skull, mandible & maxilla- teeth Amphiarthroses – partially movable joints. Examples: intervertebral disc and pubic symphysis Diarthroses – freely movable joints. The most common type of functional joint in the body. Examples: knee joint, shoulder joint, finger joints, ankle and wrist joints, etc.

Structural Classification Fibrous joints (synarthroses): adjacent bones are joined by collagen fibers. Cartilaginous joints (amphiarthroses): two bones are joined by cartilage. Synovial joints (Diarthroses): freely movable and most common joint in the body.

Joint mobility comparison Note that as mobility decreases, stability increases.

Fibrous joints (synarthroses):

Cartilaginous joints (amphiarthroses)

Synovial Joints (diarthroses) this type of joint is defined by the presence of a joint cavity filled with fluid. Most joints of the body fall into this class. Examples: knee joint, elbow joint, shoulder and hip joints and the phalanges of hands and feet, etc.

Structures in a Synovial Joint Articular capsule – tough connective tissue Joint/synovial cavity – filled with synovial fluid Articular cartilage – Hyaline cartilage Synovial fluid – viscous/ clear colorless fluid Ligaments – give the joint reinforcement and strength Nerves – provide feelings of pain and stretch 7. Vessels - provide nutrients to joint

Typical Synovial Joint

Hip Joint

Additional joint structures Ligaments- join bones to bones Consists of dense regular connective tissue. Tendons- join muscles to bone Bursae- fibrous sac lined with synovial membrane and containing synovial fluid Occurs between bones and tendons or muscles Acts to decrease friction during movement

Accessory joint structures Fatty pads - cushioning Menisci – tough fibrocartilage Bursae -flattened fibrous sac lined by synovial membrane. Tendon sheaths -fibrous tissue connecting a muscle to a bone

Knee joint structures Articular capsule Synovial membrane Medial and lateral menisci Suprapatellar, infrapatellar and prepatellar bursae Anterior and posterior cruciate ligaments Tibial and fibular collateral ligaments Patellar capsule Articular cartilage Tendon of quadriceps femoris

Knee Joint Anterior view

Knee Joint posterior view

Types of Synovial Joints Plane (gliding) Joints Hinge Joints Pivot Joints Condyloid Joints/Ellipsoidal Saddle Joints Ball and Socket Joints

Movements allowed by Synovial Joints 1. Flexion –- bending movement that decreases the angle 2. Extension – movement the increases the angle, opposite of flexion 3. Abduction –moving away from the midline 4. Adduction –movement toward the midline 5. Circumduction –movement of the limb such that it describes a cone 6. Rotation – turning the bone or limb around its long axis 7. Supination –rotating the forearm laterally such that the palm faces superiorly

Movements allowed by Synovial Joints 8. Pronation –- rotating the forearm medially such that the palm faces inferiorly 9. Inversion –- sole of the foot or toes inward or medial 10. Eversion –- sole of the foot or toes outward or lateral 11. Protraction –- moving forward in one plane 12. Retraction –- moving backward in one plane 13. Elevation –- lifting the limb or body superiorly 14. Depression –- moving the body part inferiorly 15. Opposition –- to bring the thumb and index finger tips together

Body movements

Extension and flexion

Abduction and adduction

Protraction/Retraction Pronation/Supination Opposition of thumb and pinky

Elevation/ Depression Inversion/Eversion

Circumduction