Do joints in an arthopods appendages give them flexibility and the ability to move?

Yes, jointing is critical in arthropod morphology owing to the general rigidity of the exoskeleton, and the very reason for the name of the phylum (Arthropoda loosely means "joint appendages"). Jointing provides mobility through flexion and extension of walking limbs, swimmerets, and wings; as also for signalling, digging, grasping, sensing, eating and other capabilities.