Origin · insertion · action · innervation · palpation logic. Learn patterns, then exceptions.
| Muscle | Origin | Insertion | Action | Innervation |
|---|---|---|---|---|
| Trapezius | Occiput, nuchal ligament, C7-T12 spinous processes | Lateral clavicle, acromion, scapular spine | Upper: elevate/upward rotate; middle: retract; lower: depress/upward rotate scapula | CN XI motor; cervical contributions |
| Levator scapulae | C1-C4 transverse processes | Superior medial border of scapula | Elevates/downwardly rotates scapula; assists ipsilateral cervical sidebend/rotation | Dorsal scapular + cervical nerves |
| Rhomboid major | T2-T5 spinous processes | Medial scapular border below spine | Retracts/downwardly rotates scapula | Dorsal scapular |
| Rhomboid minor | Nuchal ligament, C7-T1 spinous processes | Medial end/root of scapular spine | Retracts/downwardly rotates scapula | Dorsal scapular |
| Serratus anterior | Upper 8-9 ribs | Anterior surface medial scapular border | Protraction and upward rotation; holds scapula to thorax | Long thoracic |
| Deltoid | Lateral clavicle, acromion, scapular spine | Deltoid tuberosity | Middle abducts; anterior flexes/medially rotates; posterior extends/laterally rotates | Axillary |
| Supraspinatus | Supraspinous fossa | Greater tubercle humerus | Assists abduction; stabilizes GH joint | Suprascapular |
| Infraspinatus | Infraspinous fossa | Greater tubercle | Lateral rotation; GH stabilization | Suprascapular |
| Teres minor | Lateral border scapula | Greater tubercle | Lateral rotation, weak adduction; stabilization | Axillary |
| Subscapularis | Subscapular fossa | Lesser tubercle | Medial rotation/adduction; stabilization | Upper/lower subscapular |
| Teres major | Inferior angle/lower lateral scapula | Medial lip of intertubercular sulcus | Extends, adducts, medially rotates humerus | Lower subscapular |
| Latissimus dorsi | Lower thoracic spinous processes, thoracolumbar fascia, iliac crest, lower ribs | Floor of intertubercular sulcus | Extends, adducts, medially rotates humerus | Thoracodorsal |
| Pectoralis major | Medial clavicle, sternum, upper costal cartilages | Lateral lip of intertubercular sulcus | Adducts/medially rotates humerus; clavicular fibers flex | Lateral + medial pectoral |
| Pectoralis minor | Ribs 3-5 | Coracoid process | Draws scapula anterior/inferior; stabilizes | Medial pectoral |
| Subclavius | First rib/costal cartilage | Inferior middle clavicle | Anchors/depresses clavicle | Nerve to subclavius |
| Muscle | Attachments | Action | Nerve |
|---|---|---|---|
| Biceps brachii | Long: supraglenoid tubercle; short: coracoid → radial tuberosity/aponeurosis | Supination, elbow flexion; assists shoulder flexion | Musculocutaneous |
| Brachialis | Anterior distal humerus → ulna | Primary elbow flexor regardless of forearm position | Musculocutaneous primarily |
| Coracobrachialis | Coracoid → medial humeral shaft | Shoulder flexion/adduction | Musculocutaneous |
| Triceps brachii | Infraglenoid tubercle/posterior humerus → olecranon | Elbow extension; long head assists shoulder extension/adduction | Radial |
| Anconeus | Lateral epicondyle → olecranon/proximal ulna | Assists elbow extension/stability | Radial |
| Brachioradialis | Lateral supracondylar ridge → distal radius | Elbow flexion, strongest near neutral forearm | Radial |
| Pronator teres | Medial epicondyle/coronoid → lateral radius | Pronation; weak elbow flexion | Median |
| Pronator quadratus | Distal ulna → distal radius | Pronation | Anterior interosseous/median |
| Supinator | Lateral epicondyle/ulna → proximal radius | Supination | Deep radial |
Use the action to confirm the structure rather than digging for it. Ask for a gentle contraction, locate landmarks first, then soften the contraction before treatment. Protect axilla, anterior neck, cubital tunnel and other endangerment areas. Deep does not mean indiscriminate.