What Causes Pain In Knee When Standing Up From Bed Or Chair?

Doctor , I am 61 years old and last year during feb-mar , i started having pain around my both knees. I got my Uric acid tested and it was well with in the limits. Besides that i had my both knees X Rayed and the orthopedic surgeon diagnosed it as inflammation of ligaments and prescribed Brexin tablets which i took for about a month but the relief is only temporary. Special symptoms of my problem are that I do not feel while walking and I can walk as long as my stamina lasts . I feel pain while standing up from chair or bed . I get very severe pain when the internal included angle is less than 80 degrees and it goes on getting more severe as the angle reduces.