Why does the pectoral girdle need to be flexible while the pelvic girdle needs to be rigid?

Flexibility: pectoral girdle is more flexible-less ligaments, ball and socket joint is shallower

Security: pelvic girdle is more secure, deeper socket. there are more dislocated shoulders than dislocated hips

ability to bear weight: pelvic girdle can bear more weight-the pelvic girdle has bones that are fused (os coxa) and a joint with the sacrum. the pectoral girdle has a little bone called the clavicle connecting it to the body wall.

Explanation:

yes by elenaboo   it could cause lots of stuff