Motion
These are uniaxial synovial hinge joints. They involve the articulations between the proximal and middle phalanges, and the articulations between the middle and distal phalanges. The movements possible at these joints are flexion and extension, greater at the proximal joints than at the distal.
Stability
Each joint has its own fibrous capsule.
Stabilizing ligaments include:
-Palmar ligament
-2 collateral ligaments
The long extensor tendons give the support at the posterior aspect of the joints.
Muscles
Flexion (Proximal joints of fingers):
Flexor digitorum superfiscialis
Flexor digitorum profundas
Flexion (Distal joints of fingers):
Flexor digitorum profundas
Flexion (Thumb):
Flexor pollicis longus
Extension (Fingers):
Extensor digitorum
Extensor indicis (2nd only)
Extensor digiti minimi (5th only)
Interossei
Lumbricals
Extension (Thumb):
Extensor pollicis longus
Extensor pollicis brevis.
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