There are four (sometimes they say five) joints that form the dorsal ligament of the wrist with the dorsal surface of the forearm: 1 - C5-C6 - I-II interclavicular, 2 - I-II - P-III carpometacarpal joint at the pisiform bone, 3 - II -III - III-IV carpometacarpal joint, 4-III-IV-V - IV-V metacarpophalangeal joints. The last three joints can be called round, because their ends (articular surfaces) when viewed from above and from the sides are very close in outline to a circle. Here it is possible to extend the arm at the wrist joint and rotate the I, II, and partially III metacarpophalangeal joints.