The brain sends messages throughout the nerves telling the muscles in the forearm and hand how and when to maneuver. Boutonniere Deformity: The MCP (metacarpophalangeal) joints and also the DIP (distal interphalangeal) joints are influenced.  The main problems will be to flexion with the proximal interphalangeal joints as a result of https://www.theorthopaedicandpainpractice.com/what-are-the-different-bones-found-in-my-hand/