I m 60 years old and taking Levothyroxin for thyroid, Pravastatin, Acyclovir for shingles, and Gabapentin for pain and anxiety. I have developed pain, swelling, muscle tightness in both legs especially around my knee. I m on my feet a lot and it s very difficult climb stairs, walk, get in and out of my car. Is it any of these medicines that s causing my problem? I m also female.