Second Lumbrical Muscle of Hand

Origin

The second lumbrical muscle of hand originates from the lateral aspect of the tendon of flexor digitorum profundus that travels to the middle finger.

Insertion

The fibers of the second lumbrical muscle of hand travel inferiorly to the middle finger and insert, via a short tendon, onto the lateral aspect of the extensor expansion of the middle finger.

Key Features & Anatomical Relations

The second lumbrical muscle of hand is found in the central compartment of the hand. It is a short, wormlike, unipennate skeletal muscle. It is located:

- anterior to the adductor pollicis muscle and the second dorsal interosseous muscle of hand;

- posterior to the palmar aponeurosis;

- medial to the tendon of flexor digitorum profundus that travels to the index finger;

- lateral to the tendon of flexor digitorum profundus that travels to the middle finger.

Actions & Testing

The second lumbrical muscle of hand simultaneously flexes the third metacarpophalangeal joint and extends the interphalangeal joints of the middle finger, which occurs when the second and third dorsal interossei muscles of hand contract simultaneously with it.

The second lumbrical muscle of hand can be tested by simultaneously flexing the third metacarpophalangeal joint and extending the interphalangeal joints of the middle finger. While holding this position, an examiner tries to either extend the metacarpophalangeal joint or flex the interphalangeal joints of the same finger (Sinnatamby, 2011).

References

Sinnatamby, C. S. (2011) Last's Anatomy: Regional and Applied. ClinicalKey 2012: Churchill Livingstone/Elsevier.