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Hand Bones
• Pisiform• Triquetrum• Lunate• Scaphoid• Trapezium• Trapezoid• Capitate• Hamate
Hand Bones
Hand joints
• Carpometacarpal joint(s) – (CMC)
• Metacarpophalangeal joints – (MCP)
• Interphalangeal joints (proximal & distal)– 1st digit (IP)– 2-5 digits (PIP and DIP)
Movements of the Wrist
• flexion and extension
• adduction (ulnar deviation) and abduction (radial deviation)
Tips for the forearm muscles
• Flexors and Palmaris longus (medial epicondyle) *flexor digitorum profundus
• Extensors (lateral epicondyle)
• “carpi radialis” – radial deviation (abduction)
• “carpi ulnaris” – ulnar deviation (adduction)
Flexor carpi radialisO: Medial epicondyle of humerusI: Base of second and third metacarpals,
anterior (palmar surface)A: wrist flexion, abduction of wrist, weak
elbow flexion, weak pronation of forearm
Palmaris longusO: Medial epicondyle of humerusI: Palmar aponeurosis of 2nd, 3rd, 4th, and
5th metacarpalA: Wrist flexion, weak elbow flexion
Flexor carpi ulnarisO: Medial epicondyle of humerus,posterior
aspect of proximal ulnaI: Pisiform, hamate, and base of 5th metacarpal (palmar surface)A: wrist flexion, adduction of wrist, weak
elbow flexion
Superficial Layer (Anterior Surface)
• * Pronator teres (2nd)
• Flexor carpi radialis (3rd)
• Palmaris longus (4th)
• Flexor carpi ulnaris (pinky)
Extensor carpi ulnarisO: Lateral epicondyle of humerus, middle
two-fourths of posterior border of ulnaI: Base of 5th metacarpal (dorsal surface)A: wrist extension, wrist adduction, weak
extension of elbow
Extensor digiti minimiO: Lateral epicondyle of humerusI: Base of middle and distal phalanxes of 5th
phalangeA: Extension of little finger at MCP joint, weak wrist and elbow extension
Extensor digitorumO: Lateral epicondyle of humerusI: Four tendons to bases of middle and distal
phalanges of four fingers (dorsal surface)A: Extension of 2nd, 3rd, 4th, and 5th phalanges at MCP joints, extension of wrist, weak extension of elbow
Extensor carpi radialis brevisO: Lateral epicondyle of humerusI: Base of 3rd metacarpal (dorsal surface)A: extension of wrist, abduction of wrist,
*weak elbow extension
Extensor carpi radialis longusO: Lower third lateral supracondylar ridge
and lateral epicondyle of humerusI: Base of 2nd metacarpal (dorsal surface)A: Extension of wrist, abduction of wrist,
*weak elbow extensor, weak pronation
Superficial Layer (Posterior)
• Extensor carpi ulnaris
• Extensor digiti minimi
• Extensor digitorum
• Extensor carpi radialis brevis
• Extensor carpi radialis longus
• Brachioradialis*
Torque
• Defined as “rotary” force
• Torque is the product of linear force (F) and the force’s moment arm (d┴)
T = Fd┴
T = F┴d
• Torque is created when linear force acts away from the axis of rotation
• Joint movements are rotational movements and thus are generated from torque
Illustration of Torque
Torque and Muscle Force
Levers
• A lever is a rigid bar that rotates about an axis of rotation or fulcrum
• Levers represent the interaction of muscle torque (from linear force (F)) and resistive torque (from linear resistive force (R))
• There are three different classes of levers (Class I, II, III)
Different Types of Levers
Three Classes of Levers
• Levers will emphasize two different functions depending on the location of F and R (length of moment arm) in relation to the fulcrum or axis of rotation.
1) Large torque production2) Large ROM and speed
• Class II levers will emphasize force or torque production
• Class III levers will emphasize large ROM and speed (human body is comprised mostly of Class III levers)