Biomechanics of Joints Articulations

Joint Classifications Structural Based on anatomical characteristics Presence/absence of joint cavity Type of connective tissue that binds them Types Fibrous joint Cartilaginous joint Synovial joint

Joint Classifications Functional Type of movement they permit Types Synarthrosis-Immoveable joint Sutures Amphiarthrosis-Slightly moveable joint Intervertebral joints Diarthrosis-Freely moveable joint Shoulder, knee

Synarthrodial Joint Immovable joint Fibrous joint which can attenuate force with little or no movement Examples Sutures Syndesmoses: radioulnar, tibiofibular

Amphiarthrodial Joint Cartilagenous joint which attenuates forces Examples Synchondroses: SC Joint Symphysis: Vertebral Joint, Pubic symphysis

Diarthrodial Joint Provides mobility by permitting one body segment to rotate about another. Transmits forces from one segment to another.

Diarthrodial Joint Anatomy Articular Cartilage Articular Capsule Fibrous membrane Synovial membrane Synovial Fluid Ligament

Diarthrodial Joint Types Hinge Joint Pivot Joint Condylar Joint Ellipsoid Joint Saddle Joint Ball and Socket Joint

Flexibility vs. Stability Stability: Maintaining Joint integrity What provides joint stability

Stability vs. Flexibility Answer Joint construction Ligaments Capsule Tendons Gravity Vacuum in joint

Stability vs. Flexibility Flexibility: Describes the range of movement within a joint. Types: AROM PROM Question: What factors affect flexibility?

Flexibility vs. Stability Answer Shape of the articular surface Muscle mass Bony blocks Muscle length/flexibility Ligament length/flexibility Age

Question Describe the range of motion available at the hip joint before and after a 30-s passive stretch. Which ROM is greater? Why? Describe the range of motion available after a PNF stretch at the hip. Which ROM is greater? Why?

Levers Any elongated, rigid object that rotates around a fixed pointed called a fulcrum. Rotation occurs when an effort applied to one point on the lever overcomes a resistance located at some other point.

Lever Classes

Levers cont. The function of a lever is to impart an advantage. Advantages can be either: Exert more force against a resisting object than the force applied to the lever, for example: moving a boulder with a crowbar. Move the resisting object farther and faster than the effort arm is moving.

Classes of Levers Determined by which component (fulcrum, effort, resistance) is in the middle Class Orient. Advantage Class I: FAR Balance Class II: ARF Strength Class III: AFR Speed/ROM