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)