Stretching and strengthening exercises may help prevent widespread knee problems, including one form of what is known as "runner's knee," among physically active people, a study of army recruits found.

Nearly 25 percent of physically active people suffer from anterior knee pain (AKP) -- pain at the front of the knee that is worsened by climbing stairs or running -- and it is also the main reason new British army recruits drop out.

A study at the Defense Medical Rehabilitation Center in Surrey, the United Kingdom, followed more than 1,500 recruits during a grueling 14-week training program.

Half were told to do eight different types of exercise during every training session, focusing on strengthening their leg muscles and making them more flexible by stretching. The other half did standard military warm-up and cool-down exercises.

With traditional warm-ups, nearly 5 percent of the soldiers developed knee pain, but that number dropped to just over 1 percent among those who did the special exercises -- a 75 percent decrease, Russell Coppack and his colleagues wrote in the American Journal of Sports Medicine.

"A simple set of lower limb stretching and strengthening exercises resulted in a substantial and safe reduction in the incidence of AKP in a young military population undertaking a physical conditioning program," Coppack wrote.

"Such exercises could also be beneficial for preventing this common injury among nonmilitary participants in recreational physical activity."

Only three recruits who did the new exercises were discharged as unfit for army service, compared to 25 control subjects.

Coppack and his colleagues said that it isn't clear if the findings would hold up in the general population because people outside the military are less likely to follow a strict exercise routine.

But at the least, introducing targeted workouts in the Army could lower drop-out and injury rates, potentially saving money as well, they added.