Patient specific instrumentation (PSI) has recently been developed as a replacement for traditional instrumentation in total knee arthroplasty (TKA). The study aim was to assess efficiency via the mean total OR time using the PSI versus computer-assisted (CAS) TKAs with accuracy as a secondary endpoint. Sixty patients were randomized to CAS or PSI. A formula was developed to derive a profit ratio (PR) that incorporated costs, revenue, and total OR time. The PSI cases were 1.45 times more profitable than CAS allowing for approximately 3 PSI cases versus 2 CAS cases in one 8 hour OR day. Results from this series show that PSI improves OR efficiency, but does not improve accuracy.