The crescent-shaped cushions of rubbery cartilage—two in each knee—act as shock absorbers as people walk, run, pivot and bend. Sudden stops and twisting motions can cause the meniscus to rip or experience a more gradual tear.
Jeremy Lin is the latest pro athlete to fall victim. The popular New York Knicks point guard will have surgery this week on a small, chronic tear in his left knee and miss the rest of the season, the team announced Saturday. Last month, Red Bulls power forward Juan Agudelo, Atlanta Braves third baseman Chipper Jones and Kansas City Royals catcher Salvador Perez all had meniscus surgery.
Many skiers, cyclists, joggers, golfers and other weekend warriors also damage their menisci, as do a growing number of teens and adolescents who play sports.