All year round the treadmill represents freedom for many runners, especially in the winter months when people don’t want to stop training to brave the cold weather, snow or ice. Treadmill running poses special challenges to the knees —and setting the treadmill to a small incline can help protect these vulnerable joints, says orthopedic surgeon Kevin D. Plancher, M.D., founder of Plancher Orthopedics & Sports Medicine.

While many treadmills offer inclines ranging from 0.5 to 12 percent, not all offer every incline level in between. But for the thousands of athletes who hop on a treadmill seeking a solid — and safe — workout, Dr. Plancher offers crucial clarity regarding how to best avoid knee injury by focusing on an incline level of 3 percent.

Running on a treadmill with zero incline isn’t the same as running on flat ground, he says.

“A zero-percent incline is actually the equivalent of running at a slight downhill outdoors,” he adds. “It causes additional wear and tear to the knee and patellar tendon, which helps muscles at the front of the thigh straighten the leg.”

Higher inclines, which often require an increased effort for runners, can be hard on the knees, sometimes leading to sharp knee pain, he says.

“Many of us crank up the incline on the treadmill because it’s challenging and fun, but we are not considering how treadmill inclines affect the knee joint,” Dr. Plancher explains.

Higher Inclines Can Lead to Runner’s Knee

Treadmills come pre-programmed with incline settings for a good reason. When we run at an incline, it significantly tests our leg muscles, working muscle groups such as the gluteus maximus, quad and calf muscles and burning more calories.

“Running at a small incline can even help avoid the development of shin splints and promote endurance more than running on a level surface,” notes Dr. Plancher, also a clinical professor in Orthopedics at Albert Einstein College of Medicine in New York.

Running at sharp inclines, like up hills, can result in the painful condition known as “runner’s knee,” or known medically as patellofemoral stress syndrome. At these high-incline settings, ankle joints move less, making the knees compensate to carry the body up the hill.

Lower Inclines Safer for the Knees

Running at a slight incline of 3 percent is optimal to avoid the unnatural movement patterns caused by running on a level treadmill setting.

“Even a 1-percent incline levels out the surface beneath you, relieves the pressure on your knees and places the workload on the glutes and hamstring muscles,” Dr. Plancher adds.

“As with all things, moderation is key,” says Dr. Plancher, who lectures globally on issues related to orthopedic procedures and sports injury management. “Common sense also applies: If something hurts, stop doing it. Other activities, such as biking, swimming and using an elliptical trainer, offer similar health benefits but can give your knee joints a break and are often a good alternative.”

Dr. Plancher adds that if you are unsure about a treadmill and your knees hurt, contact an orthopedic specialist who can give you a program that is personalized and beneficial to your needs.