UNC LogoFrom professional athletes to weekend warriors, the condition known as ‘runner’s knee’ seems to be a painful and probably debilitating injury suffered by millions of people. But, till today it has been indistinct just what causes it.

However, a novel study from the University of North Carolina at Chapel Hill has focused its attention on what may perhaps be the main culprits of the condition, appropriately known as patellofemoral pain syndrome. Supposedly, this study is the first large, long-term project to track athletes from before they developed runner’s knee.

Runner’s knee is known to be the bane of various types of exercise, from running to basketball to dance. Moreover, it seems to affect one in four physically active people. If unchecked, it could possibly lead to more serious problems such as patellofemoral osteoarthritis.

For the purpose of the study, Padua along with his colleagues was noted to have examined nearly 1,600 midshipmen from the United States Naval Academy. Further, the authors appeared to have analyzed participants’ biomechanics when they first enrolled at the academy. Subsequently, they seemed to have followed them for several years to see if they developed patellofemoral pain syndrome.

“Earlier studies have usually looked at people after the problem sets in. That means that while previous research has identified possible risk factors related to strength and biomechanics, it’s been unclear whether those caused the injury, or whether people’s muscles and the way they moved changed in response to their injury,” says study co-author Darin Padua, Ph.D., associate professor of exercise and sport science in the UNC College of Arts and Sciences.

He further said that, “Patellofemoral pain syndrome can be devastating. The pain can severely curtail a person’s ability to exercise and the symptoms commonly reoccur. That said, athletes often have a high pain threshold and may ignore it. But if they do, their cartilage may break down – and if that gets to the point of bone on bone contact, nothing can be done to replace the damaged cartilage.”

The findings of the study revealed that a total of 40 participants i.e. 24 women and 16 men seemed to have developed the syndrome during the follow-up period. Participants with weaker hamstring muscles were observed to be nearly 2.9 times more likely to develop the syndrome as compared to those with the strongest hamstrings. Also, those with weaker quadriceps muscles seemed to have been approximately 5.5 times more possible to develop the syndrome.

Moreover, those with a larger navicular drop i.e. a measure of arch flattening when bearing weight appeared to have been 3.4 times more likely to suffer from the syndrome. In addition, participants with smaller knee flexion angle i.e. those whose knees bent less on landing during a jump test seemed to have been 3.1 times more prone to develop the syndrome. Padua was of the opinion that the pain associated with the condition could perhaps be elucidated by those different factors coming mutually to create a focal point of pressure between the kneecap and the underlying bone.

“Overall, these people generally have weaker quads and hamstrings. As a result, they don’t bend their knees as much when doing task, such as running or jumping. That means the contact area between the kneecap and the femur is smaller, so pressure is focused and pinpointed on a smaller area,” he explains.

Padua said that, “Also, the more a person’s arch falls when bearing weight, the more their whole leg may rotate inwards. That will mean their kneecap won’t track properly, leading to yet more pressure and more potential pain.”

The findings of the study appear to confirm that if people could possibly change the way they move and improve their leg strength, they can prevent or correct the problem. More so, daily athletes may be able to spot for themselves whether they are at risk. This could be seen if their knee crosses over the big toe when squatting or the arches of their feet collapse when landing from a jump. Also, they can stand a greater chance of developing the syndrome when they appear to unable to bend their knees much when they land.

The authors are believed to have developed a simple screening tool, called LESS (Landing Error Scoring System) for recognizing people most at risk of runner’s knee, similar conditions and of suffering anterior cruciate ligament (ACL) injuries. They are at present seemed to be examining into which exercises are best for improving the biomechanics involved.

The findings of the study have been published in the American Journal of Sports Medicine.