Anatomy, Shoulder and Upper Limb, Hand Palmar Interosseous Muscle

The palmar interossei are paired intrinsic hand muscles situated between the metacarpals (see . Intrinsic Hand Muscles). These muscles typically include 4, though occasionally 3, palmar muscles that primarily adduct the fingers. The palmar interossei also assist in flexion at the metacarpophalangeal (MCP) joints and extension at the interphalangeal joints. All interossei receive innervation from the deep branch of the ulnar nerve. Consequently, ulnar nerve injury may impair intrinsic hand muscle function, particularly finger adduction, which the palmar interossei chiefly control. The palmar interossei play a critical role in grip strength and precision tasks, making them key considerations in hand rehabilitation and postsurgical recovery. Detailed knowledge of the location and innervation of these muscles supports safer surgical navigation during procedures involving the ulnar side of the hand, reducing the risk of iatrogenic injury. Understanding the anatomy and function of the palmar interossei is essential for diagnosing and managing ulnar nerve injuries, which can compromise fine motor control and finger adduction.