INTRODUCTION TO JOINT MECHANICS AND INJURIES JOINTS are the points of contact between two connected bones. Joints can be classified according to: a)Structure  what they are made of b)Function  type and extent of movement they permit

JOINT CLASSIFICATION STRUCTURE Fibrous joints Cartilaginous joints Synovial joints FUNCTION Synarthrosis (immoveable) Amphiarthrosis (slight movement) Diarthrosis (freely moveable)

TERMS TO REVIEW LIGAMENTSLIGAMENTS : attach bone to bone : less rigid than bone : made of tough bands of white fibrous tissue that allow a certain amount of stretch  will tear if they reach their threshold : referred to as “static stabilizers” of joints as they strengthen with strength and conditioning programs TENDONS : attach muscle to bone : composed of large bundles of white fibrous protein, known as collagen : greater stretching range than ligaments : referred to as “dynamic stabilizers”

CARTILAGE : no blood supply : 3 main types (hyaline, fibrocartilage, and elastic/yellow cartilage) TISSUE PROPERTIES RIGID: resistance to injury (i.e bones are more rigid than ligaments) VASCULARITY: refers to the amount of supplied blood a tissue requires “Avascular”  ligaments and cartilage, nutritional needs met through compression not blood “Vascular”  bones and muscles, meet nutritional needs through blood ** The more vascular a tissue is, the less amount of time is recovered to recover from an injury.

FIBROUS JOINTS Tightly bounded together by connective tissue, allowing no movement (synarthrosis) These are joints between the interlocking bones of the skull, known as sutures (after birth, sutures close to become immoveable joints)

CARTILAGINOUS/ FIBROCARTILAGINOUS JOINTS The body of one bone connects to the body of another by means of cartilage, allowing slight movement (amphiarthrosis) Example: intervertebral discs

SYNOVIAL JOINTS Allow the most movement (diarthrosis). Most joints in the body are of the synovial type, however furthre classification is made according to the shape of the articulating bone end. Bony surfaces are separated by a lubricating fluid (synovia) and by cartilage These joints are also joined by ligaments Examples include: knee, shoulder and ankle

CHARACTERISTICS OF SYNOVIAL JOINTS (p. 70, fig4.1) 1.Articulating Cartilage  hyaline cartilage protects the ends of bones and allows for a smooth contact surface, while acting as a shock absorber 2. JOINT CAPSULE  fibrous capsule containing: a) synovial membrane: allows nutrients to pass b) fibrous capsule: keeps synovial fluid from leaking

3. JOINT CAVITY  the area between the two bony articulating surfaces filled with synovial fluid, which acts as a lubricant  fluid reduces friction and provides nutrients for cartilage 4. BURSAE  Small flat fluid filled sacs found at friction points between tendons, ligaments and bones

5. INTRINSIC LIGAMENTS  thick bands of fibrous connective tissue that help thicken and reinforce the joint capsule 6. EXTRINSIC LIGAMENTS  separate from the joint capsule and help reinforce the joint by attaching bones together