The palmar aponeurosis:
A. Covers the palm, including the central palm, thenar and hypothenar muscless inserted mainly into the bases of the proximal phalanges and the flexor sheaths. The palmar aponeurosis is phylogenetically the degenerated, flattened, distal part of the tendon of palmaris longus, a weak flexor of the long digits, by virtue of its insertion into the bases of the proximal phalanges and the fibrous flexor sheaths. (It also inserts into the deep transverse metacarpal ligament and some fibres extend distally along the digit). The aponeurosis is immediately superficial to the neurovascular structures in the central palm, anchoring the skin, and does not extend over the thenar or hypothenar muscles, which are freer to alter shape.