I think Mo put it well.
I experienced no knee problem during 8 months on Zoladex or for several years afterwards, although aching legs were one of the symptoms whilst Zoladex was effective. Fast forward 6 years or so and and pain in one knee became so severe my GP referred me to A&E. There, following an excruciating withdrawal of fluid it was determined I had psudo gout in the joint. Both my knees now feel weak and as if constricted by a tight bandage. Going up and down stairs has become more of an effort although it does ease somewhat if I continue to do this, which I do for the exercise. My being rather overweight puts more strain on the knee joints in particular. A full body MRI this year showed I have extensive arthritis in my joints which is a common cause of knee pain.
In short, there are a number of reasons for knee pain and drugs can be responsible. Though mainly affecting his leg muscles, a friend of mine was taken off Simvastatin by his GP because of leg pain which subsequently improved his leg problem.
Agree it is worth consulting a GP.