Background Despite the innovations in total knee arthroplasty (TKA), there is still a subset of patients who do not acquire significant relief or expected satisfaction after primary TKA. However, this subgroup of patients still gains improvements more or less in terms of objective or quantified assessments after the procedure. The purpose of our study is to explore the factors that correlate with patients' satisfaction and identify minimal clinically important difference (MCID) and minimum important change (MIC) in clinical parameters. Methods We conducted a retrospective study of 161 patients diagnosed with osteoarthritis who underwent unilateral total knee arthroplasty from January 2017 to December 2017. We collected the following parameters: body mass index (BMI), duration of disease, education level, depression state, preoperative flexion contracture angle of knee, HSS scores, 11-point NRS scores, and radiological parameters (preoperative minimal joint space width and varus angle of knee). The satisfaction was graded by self-reported scores in percentage (0-100). Results We revealed that 80.8% of patients were satisfied 3 years overall after primary TKA. HSS score change, NRS-Walking score change, age, and pre-mJSW showed significant difference between satisfied and dissatisfied group. The varus angle change revealed statistical significance according to the levels of satisfaction. Simple linear regression identified the MCID for HSS score to be 5.41 and for the NRS-Walking to be 1.24. The receiver operating characteristics (ROC) curve identified the MIC for HSS score to be 25.5 and for the NRS-Walking score to be 6.5. Conclusions In summary, we identified several factors that correlated with patients' satisfaction independently after TKA in a long term. In addition, we revealed the minimal clinically important difference (MCID) and minimum important change (MIC) for HSS and NRS score in these patients.