What Causes Weakness In The Legs From The Hips To The Calves?

I m presently experiencing weakness in my legs pretty much from the hips down. The considerable muscle soreness in the ham strings and calves, such that it is difficult to walk. Added information: I have been playing golf two or three times a week for the last several years, but been riding a cart. I also sail a 36 sailboat, but not as much as I did in previous years. I m 72 years old, I m 5 11 and weight 265 lb. I have lost 70 plus pounds over the last 14 months on a program run by Kaiser. About two months ago, I came down with a really bad summer cold. In order to sleep I used Thera Flu and Afrin quite a bit. After about six weeks, the cold has finally begun to let go and I m longer using either of those medications. During this entire time I continued to play golf, using the medications as needed, which up to about two weeks ago was quite a lot. Granted, the day after, I was usually very sore, but could recover to play again in about a day or so. Stretching religiously and using Alieve to be able to play. The weakness and soreness in my legs seems to have gotten worse as the grip of the cold lessened. I m sore enough that I m walking with difficulty. My wife has been applying Ben Gay and I ve taking quite a lot of Alieve over the entire period.