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 radialis O:. Medial epicondyle of humerus I: Flexor carpi radialis O: Medial epicondyle of humerus I: Base of second and third metacarpals, anterior (palmar surface) A: wrist flexion, abduction of wrist, weak elbow flexion, weak pronation of forearm

Palmaris longus O:. Medial epicondyle of humerus I: Palmaris longus O: Medial epicondyle of humerus I: Palmar aponeurosis of 2nd, 3rd, 4th, and 5th metacarpal A: Wrist flexion, weak elbow flexion

Flexor carpi ulnaris O:. Medial epicondyle of humerus,posterior Flexor carpi ulnaris O: Medial epicondyle of humerus,posterior aspect of proximal ulna I: 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 ulnaris O:. Lateral epicondyle of humerus, middle Extensor carpi ulnaris O: Lateral epicondyle of humerus, middle two-fourths of posterior border of ulna I: Base of 5th metacarpal (dorsal surface) A: wrist extension, wrist adduction, weak extension of elbow

Extensor digiti minimi O: Lateral epicondyle of humerus I: Base of middle and distal phalanxes of 5th phalange A: Extension of little finger at MCP joint, weak wrist and elbow extension

Extensor digitorum O: Lateral epicondyle of humerus I: 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 brevis O:. Lateral epicondyle of humerus I: Extensor carpi radialis brevis O: Lateral epicondyle of humerus I: Base of 3rd metacarpal (dorsal surface) A: extension of wrist, abduction of wrist, *weak elbow extension

Extensor carpi radialis longus O: Extensor carpi radialis longus O: Lower third lateral supracondylar ridge and lateral epicondyle of humerus I: 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

Class II levers will emphasize force or torque production 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. Large torque production 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)