Study population: Postmenopausal women over the age of 65 benefiting from the implantation of a hip prosthesis: 30 with an OP fracture of the femoral neck (15 non-MA and 15 MA, the cognitive status being determined by MMSE And IADL 1 month after the fracture) and 30 controls performed for osteoarthritis, free from OP (antecedents + bone mineral density) and MA (MMSE and IADL).