Guest Editors: Alberto Grassi (II Clinic Rizzoli Orthopaedic Institute, Bologna, Italy) and Stefano Zaffagnini (II Clinic Rizzoli Orthopaedic Institute, Bologna, Italy)

Guest Editor: Rui Yang (Montefiore Medical Center and Albert Einstein College of Medicine, USA)

Guest Editors: Sommer Hammoud (Rothman Institute at Thomas Jefferson University, Philadelphia, Pennsylvania, USA) and Robin V. West (Department of Orthopaedic Surgery, Georgetown University Medical Center, Washington DC, USA)

Guest Editor: Jaimo Ahn (University of Pennsylvania, Department of Orthopaedic Surgery, Philadelphia, PA, USA)