Background: The impact of total knee arthroplasty (TKA) on patients' informal caregivers (eg, family members, friends) has gone largely ignored. The goals of this study are to measure the impact of TKA on the caregiver and identify factors contributing to higher burden.; Methods: One hundred fifty primary TKA patients and their designated caregivers were prospectively enrolled. The Caregiver Strain Index (CSI) was completed by caregivers preoperatively, at 4 weeks, and at 1 year after surgery. Additional outcomes included the Knee injury and Osteoarthritis Outcome Score for patients only and the Veterans Rand 12 Item Health Survey for both patients and caregivers. Univariate analysis and multivariate regression modeling were performed.; Results: Mean CSI scores at 1 year were significantly lower than preoperative values (P < .01), where lower scores indicate better results. Higher mean CSI values for younger caregivers were identified preoperatively (r = -0.21, P < .01) and at 4 weeks (r = -0.26, P < .01). There were higher mean CSI values for employed caregivers preoperatively (P = .01) and at 4 weeks (P < .01). A negative correlation was identified between CSI and the caregiver's Veterans Rand 12 Item Health Survey Mental Component Score preoperatively (r = -0.15, P = .03) and at 4 weeks (r = -1.5, P = .03).; Conclusion: Caregiver burden nearly doubled in the early postoperative period, which was related to several caregiver and patient factors. However, the burden was close to zero by 1 year postoperatively. Thus, TKA is a beneficial intervention for both patient and caregiver.