7–20 % of the patients with a total knee arthroplasty (TKA) are dissatisfied without an indication for revision. Therapeutic options for this patient population with mostly a lack of quadriceps strength are limited. The purpose of this study is to evaluate the effect of six weeks low load resistance training with blood flow restriction (BFR) on the clinical outcome in these unhappy TKA patients. Thirty-one unhappy TKA patients (of the scheduled fifty patients) without mechanical failure were included in this prospective study since 2022. The patients participate in a supervised resistance training combined with BFR, two times a week during nine weeks. Patients were evaluated by the Knee Osteoarthritis Outcome Score (KOOS), Knee Society Score: satisfaction (KSSs) and the Pain Catastrophizing Scale (PCS). Functionality was tested using the Six Minute Walk Test (6MWT) and the 30-Second Chair Stand Test (30CST). Follow-up took place at six weeks, three months and six months after the start. Six weeks training with BFR provided statistically significant improvements in all the KOOS subscales compared to the baseline, especially for symptoms (55.1 (±15.4) versus 48.0 (±16.5); p<0.001), activities in daily living (50.3 (±21.1) versus 43.7 (±17.2); p<0.00) and quality of life (24.6 (±18.5) versus 17.3 (±13.0); p<0.001). The PCS reduced from 27.4 (±11.0) to 23.2 (±11.4) at six weeks (p<0.01), whereas the KSSs increased from 11.8 (±6.5) to 14.9 (±7.6) (p=0.021). Both the 6MWT and the 30CST improved statistically significant from respectively 319.7 (±15.0) to 341.6m (±106.5) (p<0.01) and 8.6 (±3.9) to 9.3 times (±4.5) (p<0.01). Blood flow restriction appears to enhance the quality of life and functional performance of unhappy TKA patients. Based on these preliminary results, BFR seems to be a promising and valuable alternative for these TKA patients with limited therapeutic options