I have been dealing with weak knees for 5 months now...have had blood work, physical therapy for 5 months, seen an arthritic doctor, an EMG and waiting for my MRI of lower spine. I was told that my knees are not centered and I should have my tendons cut to center them. Other 2 doctors claim this was unecessary. I have been riding my bicycle for a month now religously, but still have knee problems off and on. Does anyone have any ideas? My knees just feel weak...no joint pain nor any knees giving out.