I Started Taking Atorvastatin 20 Mg About Two Months Ago.

I started taking atorvastatin 20 mg about two months ago. I have also been told in the past two months (based on an MRI) that I have arthritis in my knee. I am 77 years old. My knee will definitely need further attention. I was given a shot of cortisone to help me get through a coast-to-coast move (packing, preparing two homes for new owners, etc.) Question ...... I have also been having a good night's sleep. Problems include leg cramps and general pain in my entire leg. This often causes me to get up for an hour or two every night.
I read somewhere that statins can cause leg problems. Is this true?

Bob