BACKGROUND Patients experience severe pain in early postoperative rehabilitation after total knee arthroplasty (TKA). This study aimed to compare the effect of femoral nerve block with different concentrations of chloroprocaine on postoperative rehabilitation in patients with TKA. MATERIAL AND METHODS Ninety patients who only received unilateral TKA were randomly and equally divided into C1 (1% chloroprocaine 0.2 ml/kg), C2 (2% chloroprocaine 0.2 ml/kg), or NS (0.9% sodium chloride solution 0.2 ml/kg) groups. The patients received rehabilitation 3 times a day on days 3-6 after surgery, and femoral nerve block was performed with corresponding solution 10 min before each training session. We recorded the maximum knee flexion angles (MKFA) and maximum knee extension angles (MKEA) during active exercise on day 7 after surgery, as well as the incidence of MKFA ³100°, American knee society (AKS) scores, and postoperative rehabilitation satisfaction. Adverse effects after administration in each group were also recorded. RESULTS Compared with group NS, patients in group C1 and C2 had larger MKFA during active exercise on day 7 after TKA, and had better rehabilitation satisfaction (P<0.05). MKEA, the incidence of MKFA ≥100°, and AKS scores showed no significant differences in the 3 groups. There were more patients with decline of muscle strength in group C2 (P<0.05), and no other adverse reactions were recorded. CONCLUSIONS Chloroprocaine for femoral nerve block can be safely used in rehabilitation after TKA and to improve the knee flexion angle in the early postoperative period. Because they may have fewer adverse effects, 1% chloroprocaine 0.2 ml/kg may be preferred.