Which muscles are flexors of the Metacarpophalangeal (MCP) joints? Lumbricals Dorsal and Palmar Interossei Flexor digitorum superficialis (FDS) All of the above are flexors of the MCP joints

Correct Answer: D.  All are flexors of the metacarpophalangeal (MCP) joints. The four lumbricals (Answer A.) originate in the palm from the flexor digitorum profundus (FDP) tendons.  They pass volar to the axis of rotation at the MCP joints and insert onto the extensor mechanism permitting both MCP flexion and IP extension.   The palmar interossei adduct ("PAD") the index, ring, and small fingers towards the middle finger. The dorsal interossei abduct ("DAB") the index, middle, and ring fingers.  The middle finger has two dorsal interossei to allow it to abduct to both sides.  Both the palmar interossei and dorsal interossei originate from the metacarpal shafts and pass volar to MCP axis of rotation.  They then insert onto the central and lateral bands of the extensor mechanism.  Thus they contribute also contribute to MCP flexion as well as IP extension. The flexor digitorum superficialis (FDS) has two heads with o...