The relationship between mental health and outcomes of unicompartmental knee arthroplasty (UKA) remains unclear. Poor preoperative mental health may be caused by pain and functional limitations associated with knee arthritis. We aimed at (1) investigating the effect of preoperative mental health on early outcomes and (2) assessing whether mental health improves after UKA.
Prospectively collected registry data of 1473 medial UKAs performed at a single institution in 2007-2014 were reviewed. Linear regression was used to determine improvement in mental health up to 2 years according to preoperative Short-Form 36 Mental Component Summary (MCS). Patients were stratified into low MCS (<50, n = 579) and high MCS (≥50, n = 894). The Knee Society Knee Score (KSKS), Function Score (KSFS), Oxford Knee Score (OKS), Short-Form 36, satisfaction, and expectation fulfilment were compared at 6 months and 2 years.
The mean preoperative MCS was 41.2 in low MCS group and 58.6 in high MCS group (P < .001). The high MCS group had higher KSKS, KSFS, OKS, and Physical Component Summary, and a greater proportion of patients were satisfied and had expectations fulfilled at 6 months and 2 years (P < .05). However, the low MCS group demonstrated greater improvement in KSKS, KSFS, and OKS (P < .05). Lower preoperative MCS score was predictive of greater improvement in MCS (coefficient = -0.662, R = -0.602, P < .001).
Patients with poor mental health benefit from greater improvements in their mental health and knee function after UKA, but also have a greater dissatisfaction.