The ability of human beings to walk upright is attributable to the special structure of their backs. The spine is the pillar of the human body, its 33 vertebrae being held together by various ligaments and over 140 different muscles. These also give the spine the support it needs for upright walking and, at the same time, its flexible structure.
As befits the active nature of the species, human beings are also equipped with extremely manoeuvrable arms and hands, with an impressive movement radius made possible by a sophisticated shoulder joint suspension. You should note, however, that the only place your arms are directly connected to the rest of the skeleton is at the sternum (breastbone) via the clavicle (collarbone). The scapula (shoulder blade) and shoulder joint are supported solely by the muscles, which have a correspondingly heavy workload.