Differential diagnosis of painless bilateral knee buckling?

Most commonly: at age 83 and , in fact, in people over their sixties the most common cause of painless knee buckling is QUADRICEPS weakness...There are exercises to treat this and your PCP should be able to describe these exercises. Perhaps a short course of PHYSICAL THERAPY would help (That's what I would recommend) REMEMBER knee buckling is a SAFETY ISSUE and should NOT be IGNORED! Hope this is helpful Dr Z

Knee buckling.: Buckling implies weakness of the knees, which generally could come from the joint itself (osteoarthritis) or the muscles and ligaments surrounding the knees. Weakening of the muscles would lessen the support function of the joints. Ligaments can tear from trauma or just from use over time.