Dr. Mark Tuttle explains that some knee implant problems could be caused by allergies.

"It's not very common. It's common in people who do aggressive cutting and pivoting, so exactly what Von does," explained Dr. Kareem Sobky, and...

She nearly lost an arm when she was shot at Columbine High School in 1999, but doctors saved her life and her limb. Twenty one years later, Kacey...