Dr. Gallentine joined Nebraska Orthopaedic & Sports Medicine in 2003. He was born and raised in Broken Bow, Nebraska, and received his undergraduate degree from Hastings College in Hastings, Nebraska. He continued his schooling in Nebraska, receiving his doctor of medicine from the University of Nebraska Medical Center. This was followed by an internship and residency at the Medical College of Georgia Hospital & Clinics in Augusta, Georgia. He went on to complete a Fellowship Training for Surgery of the Foot and Ankle at the Mayo Clinic in Jacksonville, Florida. In June 2010, Dr. Gallentine completed a Fellowship Training in Total Joint Replacement focusing on hip and knee replacement, primary and revisions at Wellington Hospital in Wellington, New Zealand.

Of special note, Dr. Gallentine served in the U.S. Military from July 1999 through August 2003 where he was a staff orthopaedic surgeon at Naval Hospital Charleston in North Charleston, South Carolina.