Peripheral Nerve Courses

Clinical A+K Upper Quadrant

Sciatic nerve

L4–S3. Medial to piriformis → greater sciatic foramen → posterior thigh → divides at popliteal fossa. Muscles: Hamstrings, posterior adductor magnus.

Tibial nerve

L4–S3. Apex popliteal fossa → posterior leg under tibialis posterior → tarsal tunnel → plantar branches. Muscles: Gastrocnemius, soleus, tibialis posterior, FDL, FHL, intrinsic foot muscles.

Common peroneal nerve

L4–S2. Lateral popliteal fossa → wraps fibular neck → deep to peroneus longus → superficial & deep branches. Muscles: Short head biceps femoris, peroneal muscles (via branches).

Median nerve

C5–T1. Lateral + medial cords → lateral to brachial artery → cubital fossa → pronator teres → between FDS/FDP → carpal tunnel. Muscles: Forearm flexors, thenar muscles, lateral lumbricals.

Radial nerve

C5–T1. Posterior cord → behind axillary & brachial arteries → spiral groove → lateral humerus → anterior arm → lateral epicondyle → @ lateral epicondyle divides into superficial (sensory) & Posterior Interosseous (motor) branches. Muscles: Triceps, brachioradialis, supinator, wrist & finger extensors.

Ulnar nerve

C8–T1. Medial cord → medial arm → behind medial epicondyle → between FCU heads → medial forearm → hand branches. Muscles: FCU, medial FDP, interossei, hypothenar muscles.

Musculocutaneous nerve

C5–C7. Lateral cord → pierces coracobrachialis → between biceps & brachialis → lateral cutaneous nerve of forearm. Muscles: Biceps, brachialis, coracobrachialis.

Axillary nerve

C5–C6. Posterior cord → behind axillary artery → through quadrangular space (subscapularis/teres minor above, teres major/long head triceps below, lateral border = surgical neck of humerus) → anterior & posterior branches; anterior branch curves around humeral head deep to deltoid. Muscles: Deltoid, teres minor.