Chapter 5 Joint Classifications

• Synarthroses – immovable

• Amphiarthroses – slightly movable

• Diarthroses (synovial) – freely movable

Biomechanics of Human Skeletal Articulations

Synarthroses Amphiarthroses • Immovable joints such as: • Slightly movable joints such as: – Synchondroses – Sutures • 1st sternocostal • skull

– Syndesmoses – Symphyses • Tibiofibular • Intervertebral body

Diarthroses Synovial Joint Architecture (synovial) • Articular cartilage – protective layer of • Freely movable joints dense white connective tissue covering such as: the articulating bone surfaces

• Articular capsule – a double-layered – Knee membrane that surrounds the joint

• Synovial fluid – clear, slightly yellow – Elbow liquid that provides lubrication inside the articular capsule

• Bursae – small capsules filled with synovial fluid that cushion the structures they separate

1 Synovial Joint Classifications Gliding Joint

• Gliding • Hinge • Tarsal metatarsal • Pivot • Condyloid • Saddle • Ball and socket

Hinge Joint Pivot Joint

• Humeroulnar Joint • Radioulnar Joint

Condyloid Joint Saddle Joint

• Metacarpal phalangeal Joint • 1st carpal metacarpal joint

2 Ball and Socket Joint Articular Cartilage

• Spreads loads over a wide area reducing contact stress

• Hip joint • Provides a protective lubrication that minimizes friction and mechanical wear at the joint

Articular Fibrocartilage Articular Fibrocartilage Functions

• Load distribution

• Improving joint fit

• Limiting slip between articulating bones

• Protecting joint periphery

• Joint lubrication soft-tissue discs or menisci that intervene between articulating bones • Shock absorption

Articular Connective Tissues Joint Stability

• Tendons – connect muscles to bones

• Ligaments – connect bones to bones

Ability of a joint to resist abnormal displacement of the articulating bones

3 Factors Increasing Joint Stability Joint Flexibility

• Closely reciprocating match of the • A description of the relative ranges of articulating bone surfaces motion allowed at a joint in different – Maximal stability is in close-packed position directions

• Strong array of ligaments and muscle • Range of Motion (ROM): the angle tendons crossing the joint through which a joint moves from anatomical position to the extreme limit of • Absence of muscle fatigue segment motion in a particular direction

ROM Measurement Factors Influencing Joint Flexibility

• Intervening tissues – Bone – Muscle – Fat

• Tightness/laxity in tissues crossing the joint – Muscles – Collagenous tissue • ROM is measured directionally from anatomical position (0º) • Muscle fatigue

Sensory Receptors Influencing GTO Musculotendinous Extensibility

• Golgi tendon organs – inhibit tension in muscle & initiate tension development in antagonists

• Muscle spindles – provoke reflex contraction in stretched muscle & inhibit tension in antagonists • Aid in slow, controlled stretching

4 Muscle Spindles GTO vs. Muscle Spindles Golgi Tendon Organs Muscle Spindles Location Within tendons near the Interspersed among muscle muscle-tendon junction fibers in parallel with the in series with muscle fibers fibers Increase in muscle length Stimulus Increase in muscle tension Response 1) inhibit tension development in stretched 1) initiate rapid contraction muscle of stretched muscle 2) initiate tension 2) inhibit tension development in stretched development in muscle antagonist muscles Overall Promote stretch in muscle Inhibit stretch in muscle Effect being stretched being stretched

Active vs. Passive Stretching Ballistic vs. Static Stretching

• Active Stretching – produced by active • Ballistic stretching – a series of quick development of tension in the antagonist bouncing-type stretches muscles • Static stretch – maintaining a slow • Passive Stretching – produced by a force controlled, sustained stretch over time- other than tension in the antagonist usually about 30 seconds muscles

Proprioceptive Neuromuscular Osteoarthritis Facilitation PNF • Common degenerative disease of articular cartilage Group of stretching procedures involving alternating contraction and relaxation of • Symptoms include pain, swelling, ROM the muscles being stretched restriction, and stiffness

• Both too little and too much mechanical stress seem to promote development

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