Background: This study aimed to assess the efficacy of the adductor canal block (ACB) in comparison to intra-articular steroid-lidocaine injection (IASLI) to control chronic knee osteoarthritis (KOA) pain. Methods: A randomized, single-blinded trial in an outpatient rehabilitation clinic re-cruiting chronic KOA with pain ≥ 6 months over one year. Following randomization,subjects received either a single ACB or IASLI under ultrasound guidance. Numerical rating scale (NRS) scores for pain, and Knee Injury and Osteoarthritis Outcome Scores (KOOS) were recorded at baseline, 1 hour, 1 month, and 3 months postinjection. Results: Sixty-six knees were recruited; 2 were lost to follow-up. Age was normally distributed (P = 0.463), with more female subjects in both arms (P = 0.564). NRS scores improved significantly for both arms at 1 hour, with better pain scores for the IASLI arm (P = 0.416) at 1st month and ACB arm at 3rd month (P = 0.077) with larger effect size (Cohen’s d = 1.085). Lower limb function improved significantly in the IASLI arm at 1 month; the ACB subjects showed greater functional improvement at 3 months (Cohen’s d = 0.3, P = 0.346). Quality of life (QoL) improvement mirrored the functional scores whereby the IASLI group fared better at the 1st month (P = 0.071) but at the 3rd month the ACB group scored better (Cohen’s d = 0.08, P = 0.710). Conclusions ACB provides longer lasting analgesia which improves function and QoL in chronic KOA patients up to 3 months without any significant side effects.