You head out for your morning walk, but your calves ache and your legs feel heavy. You chalk it up to arthritis and try to walk away the leg pain, but it only gets worse.

That pain may have nothing to do with your arthritis. Instead, blocked arteries in your legs, called peripheral artery disease (PAD), may be causing your leg pain. “If you can walk through the pain and it gets better as you go, it’s RA,” says Michael R. Jaff, an osteopathic physician and medical director of the vascular diagnostic laboratory at Massachusetts General Hospital in Boston. “With PAD, the more you walk, the worse the pain gets,” he says.

PAD causes muscle pain, not joint pain. But people with RA – and possibly many with OA – may be at increased risk for PAD. The conditions share some of the same risk factors: high cholesterol, high blood pressure, smoking, overweight, diabetes and a sedentary lifestyle.

“The only good way to distinguish between arthritis pain and the pain of PAD is to have an ankle-brachial index (ABI) test,” says Dr. Jaff. “An ABI is simple and noninvasive, and takes just a few minutes.” Essentially, it compares the blood pressure in your feet with the blood pressure in your arms to see how well your blood is flowing. A normal score is 1.0 or greater; a score less than 1.0 suggests PAD. The lower the score, the more severe the PAD. 

The consequences of PAD are preventable by making lifestyle changes or using medications that decrease the risk of blood clots, such as aspirin and clopidogrel (Plavix). In some cases, surgery – such as balloon angioplasty to open blocked arteries in the leg – is required. If you have pain when walking: “Get tested,” says Dr. Jaff.