What causes ‘Runners Knee’?

From professional athletes to weekend warriors, the condition known as “runner’s knee” is a painful and potentially debilitating injury suffered by millions of people – although until now, it has been unclear just what causes it.

But new research from the University of North Carolina has identified what appear to be the main culprits of the condition, formally known as patellofemoral pain syndrome.

The study, published in the American Journal of Sports Medicine, is believed to be the first large, long-term project to track athletes from before they developed runner’s knee.

Runner’s knee is the bane of many types of exercise, from running to football to dance and affects one in four physically active people. If unchecked, it can lead to more serious problems such as patellofemoral osteoarthristis.

“Patellofemoral pain syndrome can be devastating,” said Co-author Darin Padua, “The pain can severely curtail a person’s ability to exercise and the symptoms commonly re-occur. However, athletes often have a high pain threshold and may ignore it. But in doing so, their cartilage may break down and if that develops to the point of bone on bone contact, nothing can be done to replace the damaged cartilage.”

Overall, sufferers generally have weaker quads and hamstrings. As a result, they don’t bend their knees as much when doing tasks, 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.

“Earlier studies have usually looked at people after the problem sets in,” Padua said. “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.”

“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 good news is that the study appears to confirm that if people can change the way they move and improve their leg strength, they can prevent or correct the problem.

Everyday athletes can also spot for themselves whether they are at risk. If their knee crosses over the big toe when squatting, the arches of their feet collapse when landing from a jump and if they do not bend their knees much when they land, they stand a greater chance of developing the syndrome, Padua said.

The researchers are now looking into which exercises are best for improving the biomechanics involved. They have also developed a simple screening tool for identifying people most at risk of runner’s knee and similar conditions and of suffering anterior cruciate ligament injuries.

Source: Medical News Today
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Co-author Darin Padua, Ph.D., associate professor of exercise and sport science in the UNC College of Arts and Sciences is a regular contributor to Athletic Therapy Today and the Journal of Sport Rehabilitation

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