» ACL Tear
"THERE'S ONE ACL INJURY for every 2,300 skiers a day during the winter," says Dr. Robert Johnson, professor emeritus of orthopedic surgery at the University of Vermont, who estimates that he's repaired 3,000 torn anterior cruciate ligaments (ACLs), the connective tissue that keeps the shin and thighbone properly aligned. The damage, common among skiers and basketball, volleyball, and soccer players, comes from a backward twisting fall that causes the ligament to snap. The prognosis? A trip to the OR and six months of rehab.

TREATMENT: "If your doctor says you have to have surgery—which isn't always the case—you need to get your range of motion back before you go under the knife," says Johnson. "Otherwise the joint could become stiff after surgery, and you may lose some range of motion permanently."

Three times a day, take five minutes and sit on the edge of a table straightening and bending your knee as far as you can, Johnson counsels. "It should hurt while you move the leg, but not after you're done."

PREVENTION: When you fall and you know your knee is functional but hurtin', don't try to bounce back up. According to Johnson, you'll likely fall again and tear the already stretched ACL. Instead, stay down until you know for certain everything's OK, then limp down the mountain or off the court and call it a day.