The lumbricals are intrinsic muscles of the hand. There are four lumbricals – each associated with a digit.
- Attachments: Originates from the tendon of the flexor digitorum profundus. Inserts onto the radial aspect of the extensor hood of each digit.
- Actions: Flexion at the metacarpophalangeal joint and extension at the interphalangeal (IP) joints.
- Innervation:
- Lateral two lumbricals (of the index and middle fingers) are innervated by the median nerve.
- Medial two lumbricals (of the little and ring fingers) are innervated by the ulnar nerve.
- Blood supply: Superficial and deep palmar arches
By TeachMeSeries Ltd (2025)
Figure 1
The lumbricals of the hand. Note the differing unipennate and bipennate structure.