Maybe parents are right to bristle when their infatuated offspring brings home a motorcycle rider: Despite only making up 10% of vehicles on U.S. roads, motorcycle riders comprise 40% of all traffic accident trauma patients. It’s risky business—even, it appears, when you do the right thing and wear a helmet. A new study published in the Open Access journal SICOT-J has found that, while it protects from the most severe injuries, wearing a helmet during a crash is associated with more arm and hand injuries.