Orthopedic Clinical Specialist Practice Exam 2026 – Complete OCS Test Prep

Claw hand appears when the intrinsic hand muscles that the ulnar nerve supplies are paralyzed. The ulnar nerve innervates the interossei and the medial two lumbricals, and these muscles normally flex the metacarpophalangeal joints while extending the interphalangeal joints. When they’re weak or lost, the extensors pull the MCP joints into hyperextension while the IP joints remain flexed, especially in the ring and little fingers. This creates the characteristic clawing pattern. Other nerves produce different patterns of weakness (for example, median nerve injury can cause benediction or ape hand, radial nerve injury causes wrist drop, etc.), but claw hand specifically reflects loss of ulnar-innervated intrinsic hand muscles.