Number of Americans over 50 who have an artificial knee, according to the first national estimate of the how widely used the replacement joints are. Knee replacements are most common in people over 80, affecting 1 in 10 people in that age range, but the rate of the surgery has tripled since the late 1990s in relatively younger adults aged 45 to 64 — due to the obesity epidemic and overexertion by aging amateur athletes — a trend doctors think will continue. The numbers foretell a big segment of the population who may need additional knee-related care. [via Associated Press]
