Every year, Major League Baseball spends more than $1.5 billion on pitchers—five times the salary of all NFL quarterbacks combined. Pitchers are the lifeblood of the sport, the ones who win championships, but today they face an epidemic unlike any baseball has ever seen.\n\nOne tiny ligament in the elbow keeps snapping and sending teenagers and major leaguers alike to undergo surgery, an issue the baseball establishment ignored for decades. For three years, Jeff Passan, the lead baseball columnist for Yahoo Sports, has traveled the world to better understand the mechanics of the arm and its place in the sport's past, present, and future. He got the inside story of how the Chicago Cubs decided to spend $155 million on one pitcher. He sat down for a rare interview with Hall of Famer Sandy Koufax, whose career ended at 30 because of an arm injury. He went to Japan to understand how another baseball-obsessed nation deals with this crisis. And he followed two major league pitchers as they returned from Tommy John surgery, the revolutionary procedure named for the former All-Star who first underwent it more than 40 years ago.\n\nPassan discovered a culture that struggles to prevent arm injuries and lacks the support for the changes necessary to do so. He explains that without a drastic shift in how baseball thinks about its talent, another generation of pitchers will fall prey to the same problem that vexes the current one.\n\nEqual parts medical thriller and cautionary tale, The Arm is a searing exploration of baseball's most valuable commodity and the redemption that can be found in one fragile and mysterious limb.