Middle phalanges join proximal phalanges to the distal ones. These bones have two joints allowing fingers and toes to bend in two places.
Middle phalanges of fingers are very unique; whereas thumbs do not possess these bones because the only have proximal and distal phalanges.
Middle phalanges of feet are also just like hands’ phalanges and are in between distal and proximal phalanges. Except the big toe or first toe on foot four out of five toes have middle phalanges.
The most important supporting structure is the joint capsule. Additional support is provided the layers of broad tendons called “aponeurosis”. Such aponeurosis includes palmar aponeurosis of hands and plantar aponeurosis of feet.
Middle phalanges allow two movements: flexion and extension.
Flexion is about 100 degrees in proximal inter-phalangeal join (PIP) joints and restricted to 80 degrees in distal inter-phalangeal joint (DIP).
- Extension is however limited by collateral and volar ligaments.