You can do arthroplasty in a young patient, but...: Commentary on articles by John P. Meehan, MD, et al.: "Younger age is associated with a higher risk of early periprosthetic joint infection and aseptic mechanical failure after total knee arthroplasty," and Vinay K. Aggarwal, et al.: "Revision total knee arthroplasty in the young patient: is there trouble on the horizon?".