Effects of Nigella sativa oil on pain intensity and physical functions in patients with knee osteoarthritis: a comparative randomized controlled trial

Knee osteoarthritis (OA) is a degenerative joint disease characterized by pain, stiffness, and reduced mobility, which significantly impairs quality of life. Nigella sativa oil has anti-inflammatory and analgesic properties; however, clinical evidence regarding its topical use in knee OA remains limited. This study aimed to evaluate the effects of Nigella sativa oil massage, as an adjunct to standard medical treatment, on pain intensity, physical function, and knee joint range of motion (KJROM) in patients with knee OA. A randomized controlled trial was conducted with 75 patients diagnosed with knee OA. Participants were randomly assigned to three groups: Nigella sativa oil, naproxen and lidocaine gel, and vaseline. Each treatment (1 ml) was applied topically with a 2-minute massage to both knees three times daily for 21 days. Randomization was computer-generated, and sample size was determined using G*Power. Outcome measures included the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and KJROM. Effect sizes were reported as mean differences with 95% confidence intervals. Compared with the vaseline group, the Nigella sativa oil group showed greater reductions from baseline to Day 21 in WOMAC pain (between-group mean difference, − 4.56; 95% CI, − 7.99 to − 1.13; p = 0.010), stiffness (− 2.12; 95% CI, − 3.58 to − 0.66; p = 0.005), and physical function scores (− 17.32; 95% CI, − 28.61 to − 6.03; p = 0.003). After adjustment for the corresponding baseline measurements, final KJROM values were also greater in the Nigella sativa oil group than in the vaseline group for the right knee (adjusted mean difference, 4.10°; 95% CI, 1.83 to 6.36; p < 0.001) and left knee (5.84°; 95% CI, 3.73 to 7.94; p < 0.001). No adverse events were reported. Topical application of Nigella sativa oil, as an adjunct to standard treatment, may be a promising complementary approach for improving symptoms in patients with knee OA. However, given the relatively small sample size and other methodological limitations, these findings should be interpreted with caution. Larger, adequately powered, multicenter randomized controlled trials are needed to confirm these results. This study was retrospectively registered under the Clinical Trials protocol registration system (NCT05541185) on August 28th, 2022.