Background: Osteoarthritis is a chronic degenerative joint disease. Evidence on the combined efficacy of acupuncture and electrotherapy in routine practice is insufficient. Objective: This study aimed to retrospectively evaluate the impact of combining acupuncture and electrotherapy versus acupuncture alone on pain and function in osteoarthritis patients. Method: This study was a single-center retrospective observational study. Data of patients diagnosed with knee osteoarthritis and who completed at least one course of treatment from January 2020 to December 2023 were extracted from the hospital's electronic medical record system. The patients were divided into the combined treatment group (receiving acupuncture combined with electrotherapy) and the single treatment group (receiving acupuncture only). Through propensity score matching (PSM), a 1:1 ratio was used for matching, and a total of 200 patients (100 in each group) were included in the final analysis. Outcomes included changes in pain visual analog scale (VAS) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), range of motion (ROM), 12-item Short Form Health Survey (SF-12) score, efficacy rate, and adverse events. Result: The combined therapy group showed a decrease in pain VAS scores from 6.5 ± 1.2 at baseline to 4.2 ± 1.4 after treatment, representing an average reduction of 2.3 ± 1.1 points, and from 6.4 ± 1.3 to 5.0 ± 1.5 in the acupuncture-only group, with an average reduction of 1.5 ± 1.2 points. The difference between the two groups was 0.8 points (95% CI: 0.5–1.1, p < 0.001), indicating significantly greater pain relief in the combined therapy group and improvement in WOMAC (especially pain and function subscales), knee ROM, and SF-12 physical health score (all p < 0.05). The efficacy rate was higher in the combined group (94% vs. 79%, p < 0.01), with no significant difference in adverse events (p > 0.05). Multivariate regression confirmed combined treatment as an independent factor for greater pain relief (B = −0.688, p < 0.001). Conclusion: In real-world practice, combined acupuncture and electrotherapy were associated with superior pain relief and functional improvement in osteoarthritis patients without increasing risk, supporting integrated non-pharmacological management.