What structure is primarily tested during the Bunnel-littler test?

The Bunnell-Littler test is designed to assess the flexibility of the intrinsic muscles of the hand, specifically focusing on the metacarpophalangeal (MCP) joint and the proximal interphalangeal (PIP) joint. During this test, when the MCP joint is held in a flexed position, the examiner evaluates the motion available at the PIP joint. This is primarily meant to differentiate between intrinsic and extrinsic muscle tightness.

The correct answer, indicating the MCP joint, is pivotal because the position of the MCP joint directly influences the function of the intrinsic muscles and their ability to flex the PIP joint. If the PIP joint remains limited in flexion when the MCP joint is flexed, it suggests a tightness condition affecting the intrinsic muscles. Conversely, if the PIP joint flexes adequately, it indicates that the intrinsic muscles are functioning normally.

Understanding this test's focus on the MCP joint is essential for clinicians when evaluating hand and finger mobility, as it helps in diagnosing conditions such as intrinsic tightness or extrinsic tightness. This understanding aids in creating appropriate treatment plans for rehabilitation or further intervention.