Background: Osteoarthritis is a degenerative disease characterised by pain, stiffness and reduced ROM which results in difficulty in ADLs due to reduced functional performance and mobility. The purpose of this study is to evaluate and compare the effects of retro-walking on underwater treadmill along with conventional treatment and conventional treatment alone on pain, functional performance and mobility in patients with knee osteoarthritis (OA).Methods: In this experimental study, 30 subjects with knee osteoarthritis fulfilling the inclusion & exclusion criteria were selected and randomly allocated in two groups. Control group received conventional closed chain exercises for 2 weeks. Experimental group received retro-walking on underwater treadmill for 10 minutes along with the conventional exercises. Outcome measures like visual analogue scale (VAS), Western Ontario and McMaster Universities Arthritis Index (WOMAC) and timed up and go (TUG) were used for pain, functional performance and mobility respectively. Comparison of intra-group changes was made using Wilcoxon signedrank test or paired t-test for all the outcome measures. The inter-group comparison for all the outcome measures was done using Mann-Whitney U-test.Results: Inter-group analysis showed a significant reduction in pain levels and improvement in functional performance and mobility in the experimental group. (p < 0.005) Conclusion: This concludes that retro-walking on underwater treadmill group is effective in reducing the pain levels, improving functional performance and mobility in patients with knee OA than the conventional treatment alone. Hence it can be used in the protocol.