Stavros G Memtsoudis1,2, Jashvant Poeran3,4, Henrik Kehlet5,6. 1. Department of Anesthesiology, Critical Care, and Pain Management, Hospital for Special Surgery, New York, New York. 2. Department of Healthcare Policy and Research, Weill Cornell Medical College, New York, New York. 3. Institute for Healthcare Delivery Science, Department of Population Health Science and Policy, Icahn School of Medicine at Mount Sinai, New York, New York. 4. Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, New York. 5. Section of Surgical Pathophysiology, Rigshospitalet, Copenhagen University, Copenhagen, Denmark. 6. The Lundbeck Foundation Centre for Fast-track Hip and Knee Replacement, Copenhagen, Denmark.