I'm having symptoms that I worry may indicate a circulatory issue. For the last two months, I've experienced a crampy kind of pain in the back of my right leg below the knee, typically upon getting up in the morning or upon rising after sitting for a long time. The pain goes away quickly once I start walking, and doesn't bother me if I'm sitting still or lying down.

At first, I thought I had bruised my leg against something (always a possibility since I tend to be a bit clumsy), but I think pain from that would have disappeared by now. I'm a frequent exerciser, riding an exercise bike several times a week and also a stair climbing machine about once a week. The stair climbing is a more recent thing, and I wonder if it could be the cause, though I don't feel any worse after using the machine. I never feel any pain when I exercise.

I'm 36, and at my last check-up I was in perfect health (last May). I'm 5'7, 138 pounds; my blood pressure is 110 over 70 and my cholesterol is 160. No one in my family has had early heart or circulatory problems.

Thoughts?