Movements
The only movements permitted in the interphalangeal joints are flexion and extension.
- Flexion is more extensive, about 100°, in the PIP joints and slightly more restricted, about 80°, in the DIP joints.
- Extension is limited by the volar and collateral ligaments.
The muscles generating these movements are:
| Location | Flexion | Extension |
|---|---|---|
| fingers | the flexor digitorum profundus acting on the proximal and distal joints, and the flexor digitorum superficialis acting on the proximal joints | mainly by the lumbricals and interossei, the long extensors having little or no action upon these joints |
| thumb | the flexor pollicis longus | the extensor pollicis longus |
The relative length of the digit varies during motion of the IP joints. The length of the palmar aspect decreases during flexion while the dorsal aspect increases by about 24 mm. The useful range of motion of the PIP joint is 30-70°, increasing from the index finger to the little finger. During maximum flexion the base of the middle phalanx is firmly pressed into the retrocondylar recess of the proximal phalanx, which provides maximum stability to the joint. The stability of the PIP joint is dependent of the tendons passing around it.
Read more about this topic: Interphalangeal Articulations Of Hand
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