My 6 Year Old Granddaughter Has Been Complaining About Her

my 6 year old granddaughter has been complaining about her legs, arms, wrists and fingers hurting. Yesterday she was good. Playing and getting around. In the evening she complained about her legs again and started walking stiff legged. She was hardly able to sleep last night. This morning she had to just lay on the couch and when someone picked her up she said she hurt and started crying.