Although this knee pain
could be due to osteoarthritis
of knee but chances of lack of VIT D and calcium appear to be more.
Since you are regularly taking thyroxine
,the chances of calcium deficiency
are more and hence you must take regular calcium and VIT D.
Consult your doctor and get the prescription for VIT D and calcium made.
Also do regular quadriceps exercises to strengthen your quadriceps muscle and knee joint.
You may consult a physiotherapist and learn the way to do these exercises.