The following Healthcast report by medical editor Marilyn Brooks first aired Dec. 8, 2004, on Channel 4 Action News at 5 p.m.

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Michelle Mehling has always had a love of sports. She'll tell you there are few things in life that can make her feel so invincible -- and so vulnerable. Twice, she has torn the ligaments in her knees while playing sports.

Mehling, anterior cruciate ligament (ACL) patient: "It was the weirdest feeling I've ever felt in my life. I could actually feel the ligaments snap in half."

That "snap" or "pop" sound at the time of the injury is followed by severe pain and swelling around the knee.

More and more women are experiencing that feeling, but it's not surprising to doctors. Sports are booming for girls and women, and some in particular are posing problems.

Dr. Christopher Kaeding, Sports Medicine Center, Ohio State University: "Almost 60 percent of the females who underwent an ACL reconstruction here at Ohio State tore their ACL doing three different activities -- basketball, soccer and downhill skiing."

Among college soccer and basketball players, women tear ACLs two to four times as often as men, according to the National Federation of State High School Associations 2003-2004 athletics participation survey.

Research suggests the difference may be in the way men and women jump.

Kaeding: "The male basketball players landed much more deeply. They bent their hips and knees. The female basketball players landed much more upright, with the knee and hip more extended."

Athletes who tear their ACLs are often put on a rehabilitation program designed to strengthen the legs so they can better support the knees.

Experts have come up with an additional approach. They are training women and girls how to land and turn differently, hoping to prevent countless injuries during games and countless weeks on the bench after games.

Most ACL tears are non-contact. Besides the jumping action, sudden stops while changing direction causes most of them.