Gregg R. Klein, M.D. Make an Appointment. Hip. Knee. *For an appointment, please call 888-636-7840. **Accepting All Major Insurances**. Dr. Gregg Klein is a board certified orthopaedic surgeon specializing in hip and knee replacements as well as revision surgery. He currently serves as the Vice-Chairperson of the Department of Orthopaedic ....