The ulnar nerve innervates most intrinsic hand muscles (dorsal and palmar interossei, hypothenar muscles, and the medial two lumbricals), while the median nerve supplies only the "LOAF" muscles (lateral two lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis); this differential innervation explains why ulnar nerve injury produces claw hand—unopposed action of the spared long flexors (median-innervated in part) against paralyzed intrinsic muscles causes metacarpophalangeal joint hyperextension with interphalangeal joint flexion. The severity of clawing paradoxically depends on lesion level: a proximal (high) ulnar lesion also denervates the flexor digitorum profundus, reducing interphalangeal flexion and thus lessening visible clawing, whereas a distal (low) lesion spares the flexor digitorum profundus, producing more pronounced clawing—a phenomenon termed the "ulnar paradox." This is a topic in clinical/functional anatomy concerned with peripheral nerve innervation patterns of the hand and their diagnostic clinical correlates.
The ulnar nerve innervates most intrinsic hand muscles (dorsal and palmar interossei, hypothenar muscles, and the medial two lumbricals), while the median nerve supplies only the "LOAF" muscles (late…