The Biomechanics of Human Skeletal Articulations Chapter 5

Flashback Classification of joints According to Structure 1-Synarthroses Sutures (Joints of skull) Syndesmoses (Coracoacromial) (Radioulnar) 2- Amphiarthroses Synchondroses (sternocostal) symphyses (pubic symphysisi) According to Structure 3-Diarthrosis Gliding ( Intertarsal) (intermetatatsal) Hinge (knee,Elbow ) Pivot (Altantoaxial ) Condyloid (1st metacarpophyrengeal) Saddle ( carpometacarpal of thumb) Ball and Socket ( Shoulder) According to Axis 1-UniAxial 2-Bi-Axial 3-Poly Axial 4-Non Axial

Quick Test

Articular cartilage Dense, white connective tissue Lubricate joint 1 to 5 mm thick Soft, porous and permeable hydrated layer Function Spreads load Reduces friction Consists of Chondrocytes, collagen fibers, proteoglycans and noncollagenous proteins Under loading Deform and exude synovial fluid in area under load Sucked in from other area Permeability is decreased in area under load Cartilage matrix resist, fluid sustain pressure

Functions of Articular cartilage Cartilage can reduce load upto 50% Cartilage of knee increases in volume with height Vigorous sport cause faster accumulation Male tend to gain faster

Joint Architecture Articular Fibrocartilage soft-tissue discs or menisci that intervene between articulating bones

possible functions of Articular fibro cartilage distributing loads over joint surfaces improving the fit of articulations limiting slip between articulating bones protecting the joint periphery lubricating the joint absorbing shock at the joint

Articular connective tissues Tendons - connect muscles to bones Ligaments -connect bones to other bones Properties: Do not have ability to contract Slightly extensible If injured..only by surgery Hyperthorphy and atrophy Strength in proportionate to its antagonist Acl to quadriceps Heal and regenerate Semitendinosus

Joint Stability (Ability of a joint to resist abnormal displacement of the articulating bones)

Joint Stability What factors increase joint stability?

Shape of articulating bone Close pack position Maximum contact area Stability is maximum Loose pack position Contact area is reduced Stability is compromised

Shoulder Position: Closed Packed Position The closed packed position of the GH joint is abduction and external rotation. Open Packed Position The open packed position of the GH joint is around 50 degrees of abduction with slight horizontal adduction and external rotation Hip Position Closed Pack: Full Ext and medial rotation Open Packed Position combined flexion, abduction, and external rotation

Arrangement of ligament and muscle Disuse or overstretched Angle of muscle of pull Joint compression and stability When muscles are fatigued, cause injury to ligament and joint

Other connective tissue Fascia A fascia is a structure of connective tissue that surrounds muscles, groups of muscles, blood vessels, and nerves, binding some structures together, while permitting others to slide smoothly over each otherconnective tissue Iliotibial band The iliotibial tract or iliotibial is a longitudinal fibrous reinforcement of the fascia latafascia lata

Quick Test

Think Hard What if Menisus is being removed? 1. Is it possible? 2. Will that person be able to walk? 3. Will that person be able to bear weight? 4. Will that person be able to run? 5. Will he be able to live normal life?

Joint Flexibility What is joint flexibility? (a description of the relative ranges of motion allowed at a joint in different directions) Range of motion (ROM): the angle through which a joint moves from anatomical position to the extreme limit of segment motion in a particular direction

Joint Flexibility Range of motion is measured directionally from anatomical position (zero).