Upper limb
Extensor Digitorum
Musculus extensor digitorum
- Origin
- Lateral epicondyle of the humerus (common extensor tendon)
- Insertion
- Extensor hoods (dorsal aponeuroses) of the index, middle, ring, and little fingers, with extensions to the base of the middle and distal phalanges
- Function
- Extends fingers 2 through 5 at the metacarpophalangeal joint and assists wrist extension
- Innervation
- Radial nerve (deep branch/posterior interosseous nerve), C7–C8
- Movement & chain
- Works together with the lumbricals and interossei via the extensor hood for coordinated extension of the interphalangeal joints; necessary for releasing a grip.
- Palpation
- The four tendons are clearly visible and palpable on the dorsum of the hand during active finger extension.
- Clinical
- A classic site for tendon rupture in rheumatoid arthritis (caput ulnae syndrome) or for wrist drop caused by radial nerve palsy.
- Segmental innervation
- Part of the C7–C8 myotome; loss of function here is characteristic of wrist drop in a radial nerve lesion.
- In clinical practice
- Skin and pressure point inspection; maintain comfortable positioning and proper body mechanics during patient handling and daily care.
- Region in the model
- Upper limb