Christopher S Ahmad, MD - ColumbiaDoctors-693 White Plains Road

Justin K. Greisberg, MD, is an orthopedic surgeon specializing in foot and ankle reconstruction and complex musculoskeletal trauma. Dr. Greisberg is Chief ofFoot & Ankle Orthopedics, Chief of Orthopedic Trauma, at NewYork-Presbyterian-Lawrence Division, andProfessor of Orthopedic Surgery, Columbia University.Dr. Greisberg is an expert on complex reconstructive surgeries, limb realignment, diabetic reconstruction, Achilles tendon injuries, stress fractures, and total ankle replacement. His practice leverages advanced minimally invasive arthroscopic techniques, combined with the latest medications, braces, and orthotics to ensure accelerated recovery times.Following medical school and residency training, Dr. Greisberg completed advanced fellowship training in both foot and ankle surgery and orthopedic trauma. As chief of the foot and ankle service at Columbia University Irving Medical Center, Dr. Greisberg's practice based in Manhattan and Westchester County is supported by the full resources of the NewYork-Presbyterian Hospital system, and he frequently receives emergency trauma cases from across the region. In addition to his clinical practice, Dr. Greisberg is also a highly respected scholar who is conducting several research trials on foot and ankle procedures and trauma surgery. He co-authored a textbook, Core Knowledge in Orthopedics: Foot and Ankle, and numerous peer-reviewed articles that have appeared in professional medical journals. Dr. Greisberg is actively involved in the education of medical students and orthopedic residents and is frequently invited to lecture on complex problems of the foot and ankle at major medical conferences.

Michael L. Knudsen, MD, is a board certified and established orthopedic sports medicine surgeon specializing in the operative and non-operative treatment of athletes and non-athletes with shoulder and elbow injuries, including children, adolescents, and adults of all ages. He is an expert in minimally invasive arthroscopic and open surgery of the shoulder and elbow, and has expertise in advanced shoulder and elbow reconstructive surgery, including shoulder replacement surgery, rotator cuff tear surgery, shoulder instability and labral tear surgery, elbow arthroscopy, and elbow ligament reconstruction and repair. Dr. Knudsens practice leverages advanced imaging modalities to create personalized treatment plans and reconstructions for shoulder and elbow reconstructive surgery. He uses cutting-edge techniques for sports injuries such as PRP, ultrasound, and up-and-coming physical therapy and rehabilitation techniques such as blood flow restriction therapy.After receiving a B.S. in Biochemistry from the University of Minnesota, Dr. Knudsen completed medical school and orthopedic surgery residency at the University of Minnesota Medical School in Minneapolis. Following residency, he completed the prestigious Columbia Shoulder and Elbow Fellowship with the Department of Orthopedic Surgery at Columbia University Irving Medical Center. Dr. Knudsen returns to Columbia after starting his practice at the University of Minnesota and serving as team physician for the Minnesota Twins (Major League Baseball), Saint Paul Saints (AAA Major League Baseball), and the University of Minnesota (NCAA Division I College). During his training at Columbia, he served as an Assistant Team Physician for the New York Yankees (Major League Baseball), Rockland Boulders (Can-Am Association of Professional Baseball), and Columbia University Athletics. Dr. Knudsen currently serves as a Team Physician for Iona College where he cares for student athletes with shoulder and elbow injuries.Dr. Knudsen has a passion for research and has published dozens of peer-reviewed articles and book chapters on various topics related to shoulder, elbow, knee, and sports medicine surgery. Dr. Knudsen serves as an Associate Editor for the Journal of Shoulder and Elbow Surgery Reviews, Reports, and Techniques and actively reviews articles for the Journal of Bone and Joint Surgery, American Journal of Sports Medicine, and the Journal of Shoulder and Elbow Surgery among others. Dr. Knudsens ongoing research is focused on improving patient outcomes by improving the longevity and durability of shoulder arthroplasty implants and maximizing rotator cuff repair and labral tear healing rates. He is an active and engaged member of numerous professional organizations, including the American Academy of Orthopedic Surgeons (AAOS), the American Orthopaedic Society for Sports Medicine (AOSSM), and the American Shoulder and Elbow Surgeons (ASES).

Dr. Charles A. Popkin specializes in pediatric, adolescent, and collegiate sports medicine, with an emphasis on the operative and non-operative treatment of complex knee disorders. His specific clinical interests involve primary and revision ACL reconstruction, patellar instability, cartilage injuries and disorders, meniscal tears, and recalcitrant patellar tendinopathy. With dual fellowships in Pediatric Orthopedics and Sports Medicine, Dr. Popkin has dedicated his career to the comprehensive treatment and prevention of injury in developing athletes. He has a particular interest in the management of ice hockey injuries, serving as a team physician for USA Hockey, and on the USA Hockey National Safety and Protective Equipment Committee. Dr. Popkin is also the head team physician for: Fordham University, Mercy College, and the Hackley School in Tarrytown. In addition to his academic practice, Dr. Popkin conducts research on ACL injury prevention, ACL reconstruction techniques in the pediatric athlete, overuse injuries in youth sports, refractory patellar tendonitis, and shoulder instability in ice hockey. He pens a monthly "Ask Dr. Hockey" column for USA Hockey Magazine. Dr. Popkin lives in Westchester and enjoys spending time with his wife and two sons.