Ligament · Hand

Deep transverse metacarpal ligament

Ligamentum metacarpale transversum profundum

Three short bands that link the palmar plates of the knuckle joints of the index, middle, ring and little fingers, tying the four metacarpal heads to one another. The thumb is left out of the chain, and that omission is precisely why the thumb column can swing away from the hand while the four fingers stay in rank. The ligament is also the landmark that separates the two sets of small hand muscles: the lumbricals pass in front of it, the interossei behind. By capping how far the metacarpal heads can spread, it holds the transverse arch of the palm — the shallow curve that lets a hand wrap a cylinder instead of lying flat against it.