BACKGROUND: As the United States health-care system transitions to a value-based model, the minimal clinically important difference (MCID) has become an important metric for assessing perceived benefit in clinical settings. However, there is substantial ambiguity surrounding the MCID value because the calculation method used can lead to substantial changes in the clinical interpretation of surgical success. METHODS: A total of 1,113 patients who underwent either total knee arthroplasty (TKA) or total hip arthroplasty (THA) between June 2021 and June 2023 and completed their patient-reported outcomes (the KOOS JR [Knee injury and Osteoarthritis Outcome Score for Joint Replacement] or HOOS JR [Hip disability and Osteoarthritis Outcome Score for Joint Replacement]) preoperatively and at 1 year postoperatively were reviewed for this study. The MCID values for the HOOS JR and KOOS JR were determined using 16 statistically appropriate methods, and the resulting MCID values were applied to the study group to assess how differences in methods changed the number of patients who met the MCID at 1 year postoperatively. RESULTS: The study cohort consisted of 570 patients who underwent TKA and 543 who underwent THA. The overall cohort was 62.2% female, had a mean age of 69.3 ± 8.3 years, and was 92.3% Caucasian, 2.9% African American, and 4.8% other race (i.e., Asian, multiracial, or "other"). The MCID values varied substantially among the methods evaluated. The mean MCID was 11.5 ± 9.2 (range, 0.5 to 36.6) for the KOOS JR and 12.2 ± 8.9 (range, 0.6 to 34.3) for the HOOS JR. Distribution-based methods led to smaller but more variable MCID values, whereas anchor-based methods were noted to have larger but more consistent MCID values. CONCLUSIONS: Different statistical approaches resulted in substantial variation in the MCID threshold value, which affected the number of patients who reached the MCID. This study demonstrates the ambiguity of the MCID and casts some doubt regarding its utility for assessing the surgical benefit of total joint arthroplasty. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.