Off the circuit for a while

I have had a problem with my knees giving way on me when trying to run over the past three years.  The pain has been getting worse and at times its unbearable.  I have had tests and x-rays and it seems I have osteoarthritis in my knees, my left being the worse as there is no cartilage left its just bone on bone.  This is a major set back for me.  I don't know where I go from here. :(