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New York (Reuters Health) - Young basketball and volleyball players' chances of developing a painful condition called jumper's knee may hinge on how far they can flex their ankles, say Swedish researchers.
Teenagers at a junior elite basketball camp who were less able to flex their feet upward at the start of the study had up to a 30 percent risk of developing patellar tendinopathy -- pain below the kneecap -- over the next year, compared to a two percent risk in young players with more flexible ankles.
The notion that ankle stiffness might lead to knee pain "makes perfect sense" physiologically, said Dr. Rachel Coel, co-director of the sports medicine program at Children's Hospital Colorado, in Aurora, who was not involved in the study. "If we don't have the right flexibility, we are changing the mechanics we're supposed to have," she told Reuters Health.
Ludvig Backman and his colleagues at Umea University in Sweden, who published the new findings in the American Journal of Sports Medicine, conclude that identifying kids at risk at the beginning of a sports season and giving them preventive stretching exercises could save many young knees from damage.
So-called jumper's knee is poorly understood, but believed to stem from damage to the tendon connecting the kneecap to the shin. The condition is most common in sports like volleyball and basketball, where jumping is a frequent part of the play.
The study included 75 Swedish junior elite basketball players, both girls and boys, ages 14 to 20, who were attending a training camp. At the outset, the researchers measured each player's range of dorsiflexion -- the ability to flex the foot toward the shin. Mobility in that direction basically reflects the stiffness of calf muscles and Achilles tendons. A year later, they evaluated the players for knee pain.
A dozen athletes (16 percent) developed jumper's knee within the year; eight were male and four were female, although the sex difference was not statistically meaningful. Players who developed knee problems were found to have about five degrees less ankle mobility than those who did not experience the condition.
In players whose dorsiflexion range was under 36.5 degrees, the risk of developing jumper's knee was between 18.5 and 29.4 percent. Those with flexibility of more than 36.5 degrees had a risk of just 1.8 to 2.1 percent.
Within the ranges, researchers found that players' non-dominant legs tended to have lower degrees of dorsiflexion and significantly higher risks of jumper's knee. A history of two or more ankle sprains was also linked to poorer dorsiflexion in the affected ankle.
Inflexible ankles are not a permanent curse, however. Stretching the calf muscles and mobility training of the ankle itself can improve the joint's range of motion, as can physical therapy, according to the researchers.
Screening young athletes who can't flex their ankles as much as 36.5 degrees at the start of a sports season and working to make the joint more mobile could spare them from knee pain in the future, they say.
Doctors typically treat jumper's knee with rest and physical therapy, as well as anti-inflammatory drugs and, for more severe cases, injections of corticosteroids. Surgery is a last resort of people with persistent problems.
"The nice thing about this study is that this is a potentially fixable problem," agreed Dr. C. David Geier, Jr., director of sports medicine at the Medical University of South Carolina, in Charleston, and a spokesman for the American Orthopaedic Society for Sports Medicine. "This would be a really straightforward thing to address and might prevent some cases of patellar tendinopathy."
Source: bit.ly/pOWJLN American Journal of Sports Medicine, online September 14, 2011.