1. McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
2. Translational Musculoskeletal Research Center, Philadelphia Veterans Affairs Medical Center, Philadelphia, PA 19104, USA.
3. Department of Trauma Surgery, Regensburg University Medical Center, 93053 Regensburg, Germany.
4. Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, and North Carolina State University, Raleigh, NC 27695, USA.
5. Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
6. Collaborative Research Partner, Acute Cartilage Injury Program of the AO Foundation, 7270 Davos, Switzerland.