Research Report: Runner’s Knee, Hip Strength, and Foot Strike

woman runningWomen with patellofemoral pain syndrome shown to have greater hip adduction

A two-year, prospective study published in Medicine & Science in Sports & Exercise found that female runners who developed patellofemoral pain syndrome (runner’s knee) exhibited significantly greater hip adduction during their initial running gait assessment than women who remained injury free. Two other variables measured in the study, rear foot reversion angle and hip internal rotation, were not found to be a risk factor for developing knee pain.

This research adds to the mounting body of evidence that suggests hip weakness, and more specifically the inability of the muscles around the hip to control the motion of the leg moving inward, is a major risk factor in runner’s knee. More research is required to determine what other biomechanical or strength issues play a role in the condition, but a consistent message coming from recent research is that hip weakness is a likely predictor of knee injuries. This current study makes a strong case that hip strengthening should be a priority for runner’s, and particularly female athletes concerned about knee health.

Quadriceps muscle activity identical between people with and without anterior knee pain

Another recent study published in Medicine & Science in Sports & Exercise investigated whether or not people with patellofemoral symptoms showed a difference in the activity of their quad muscles during a squat. MRI image was used to examine the quadriceps muscle group in both people with anterior knee pain and pain-free individuals. The results of the study showed there was no difference in the way the two groups recruited their quadriceps to perform a squat based on the MRI results. These findings suggest that quad dysfunction may not be a factor in runner’s knee as was once typically thought.

One of the prevailing theories on knee pain suggests that, since the kneecap is directly attached to the quadriceps tendon, a strength deficit in the quads would lead to unwanted motion of the knee cap which would then produce the familiar symptoms of runner’s knee. Current research seems to indicate that the knee, positioned between the hip and ankle, is more influenced by motion at those joints than any factors directly at the knee itself.

This study is probably only one piece of the puzzle, and the conclusions that can be drawn from these results are somewhat limited. The researchers did not actually measure strength in the study, and a squatting motion was used to obtain the data, so the findings may not necessarily apply to runners. Quad weakness may still prove to be a factor in runner’s knee, but currently the weight of evidence favors dysfunction of the hip plays a much larger role. Although the first study referenced found no connection between foot mechanics and knee pain, I still have a strong suspicion that the knee is also influenced by the motion of the foot and ankle, but that association is difficult to establish in that there still is not a good way to properly measure these motions for injury risk factor studies. Even though stretching has gotten some bad press in recent years, decreased flexibility in muscles such as the rectus femoris crossing the hip and knee could also likely factor into the etiology of knee pain.

Variation of Footstrike in Barefoot Runners

Another interesting study that came out early this week from George Washing University, found that running foot strike patterns among habitually barefoot populations vary between forefoot, midfoot, and heel striking depending on several factors including speed and the hardness of the ground being run on. This study directly contradicts early studies that suggested barefoot runners naturally adopt a forefoot running style to reduce impact forces. The researchers studied running habits of a modern, habitually barefoot population in northwestern Kenya. The study found that at slower speeds, the runners tended to favor a rearfoot, or heel striking pattern. One possible explanation is that at endurance speeds, heel striking has an energy-saving advantage over a forefoot strike. These reports are sure to add fuel to the debate over what constitutes good running form.

Photo Credit: wwward0

Comments

  1. says

    Really interesting stuff! I would have thought hip internal rotation with gait would cause knee pain given the link between adduction and hip IR. Its nice to see some research suggesting quad strengthening is not the be all end all of pfps treatment. Lastly, very interesting barefoot study. I guess we need to continue researching this topic to get more answers. One question: Which research journals do you read through regularly?

    • James says

      Thanks Dan! I agree with you about internal rotation being a likely factor, it just didn’t appear to be an issue for that one study. It was nice to see some prospective research being done and hopefully we’ll see more like it in the future. As far as journals, I use Google Reader to subscribe to the physical therapy or sports medicine related journals that offer RSS feeds. Three that I usually look at regularly are the American Journal of Sports Medicine, JOSTP, and Medicine & Science in Sports & Exercise.

      • says

        Thanks James, I use google reader too, it’s great. Thanks for the tips. I like british journal of sports medicine too. Couple gems pop out of there every so often.

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