Knee pain can stop you from hopping on the treadmill to get in a good cardio workout. While knee pain should never be ignored, sometimes all it requires to alleviate the pain are a few changes to your gear and an understanding of your running or walking mechanics.
Chronic knee pain should be addressed by your doctor, especially if it occurs after a treadmill workout and never resolves. You may have ligament or tendon issue that can only be addressed with medical intervention.
However, if your knee pain comes on after a treadmill run and resolves itself after a day or two, you may have something commonly known as runner's knee, or Chondromalacia of the patella. Runner's knee happens when your kneecap moves slightly out of track and you pound out mile after mile, resulting in worn down cartilage.
The more you run, the more vulnerable you are to runner's knee. If you find yourself hitting the treadmill more often recently, it might be the increase in miles contributing to your knee pain. Remember to gradually increase your miles from week to week, never increasing more than about 10 percent per week. This means if you cover 20 miles in one week, you shouldn't go much longer than 22 miles the next week.
Symptoms of runner's knee include pain when descending stairs and stiffness in the joint after you've been sitting for a while. Muscle imbalances have likely caused your knee to fall off track, so strength-train your lower body — particularly your buttocks, hips and thighs — to help resolve the condition.
Make sure you have the right shoes for your gait, too. Have a running store representative watch you run and perform an analysis to see if you tend to turn in (pronate) or turn out (supinate) and suggest shoes appropriate for your particular pattern.
Read More: Stretches to Improve a Runner's Knee
When you run outside, even on pavement, gentle alterations in the terrain or natural adjustments to your speed and stride length vary the way your knees are stressed as you run or walk.
A treadmill, however, makes you particularly vulnerable to knee overuse because of the nature of the moving belt. As you run or walk to keep up with the set speed, you continuously hit the knee joint at a consistent angle. This means you're stressing the same point in the joint over and over again with no variety. The result of the treadmill's predictable, never-changing terrain are knees that feel sore sooner than they might when you run outside.
Up the Incline
Walking or running on a level treadmill puts more stress on your knee joint because your effort to keep up with the speed makes it so your feet hit the treadmill slightly forward of your body with each step. This encourages the foot to land ahead of the hip, rather than right under it, which puts additional load on the knee.
To correct this problem, walk (or run) with the belt at an incline of 5 percent or greater. You'll get a better fitness challenge, burn more calories and, as a study in the Journal of Biomechanics published in 2012 showed, work your hamstrings and quadriceps more.
As pointed out in research published in Lower Extremity Review in 2014, walking on an incline of 10 to 15 percent is an effective rehab for people under knee rehabilitation.
Read More: How to Treat Sore Knees from Running