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Effect of Melilotus Officinalis Oil on Knee Joint Pain

Objectives: Osteoarthritis is one of the most common diseases among older people which is one the most important causes of disability and heavy socio-economic burden on the elderly and society. This study aimed to investigate the effect of melilotus officinalis oil on knee joint pain and stiffness among older adults with mild to moderate primary knee osteoarthritis. Methods & Materials: This is a double-blind randomized controlled clinical trial (registration code: IRCT2016082129461N1). Participants were 61 eligible older adults (35 females and 26 males with a mean age of 78±7.79 years) residing in one of the nursing homes in Tehran, Iran who had mild to moderate knee osteoarthritis clinically diagnosed by an orthopedic physician. Then they were assigned randomly into two groups of intervention and control received melilotus officinalis oil and diclofenac gel, respectively, using a randomization table based on balance block randomization. The data were collected using a demographic form and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) for evaluating knee joint pain and stiffness at baseline, 2 weeks and 4 weeks after the intervention. Collected data were analyzed in SPSS V. 23 software.  Results: There was no statistically significant different between the intervention and control groups in terms of sociodemographic variables (age, education, marital status, occupation, smoking, physical activity, chronic illness, and medication) at baseline. Knee pain (F1,58=119.07, P<0.001) and joint stiffness (F 1,58=19.9, P<0.001) reduced significantly in both groups, where the effect size was higher in the intervention group. No considerable side effect reported during the study. Conclusion: Compared to diclofenac gel, melilotus officinalis oil can reduce knee joint pain and stiffness in older people with mild to moderate knee osteoarthritis. Therefore, it is suggested for treatment of people with knee osteoarthritis. Further studies are recommended to investigate the mechanism of melilotus oficinalis oil in reducing knee pain and stiffness and determine its effective dosage. 


Methods & Materials
This is a double-blind randomized controlled clinical trial (Registration Code: IRCT2016082129461N1) conducted on 62 older people aged <60 years living in a nursing home in Tehran with mild to moderate KO diagnosed by an orthopedic physician, who had signed a consent form. Demographic information and joint pain and stiffness were measured using the Western Ontario and McMaster Universities Arthritis Index (WOMAC). Participants were assigned to intervention and control groups using a randomization table based on balanced-block randomization receiving melilotus officinalis oil and diclofenac gel, respectively. The intervention group used 5 drops of melilotus officinalis oil in front of the knee, and the control group used diclofenac gel twice the day (morning and night).
Data were collected before the study and at the end of the 2 nd and 4 th weeks of intervention by a questioner who was not aware of the Objectives of the study, and then entered into SPSS V. 23 software for analysis. Frequency distribution, percentage, mean and standard deviation were used to describe the data, and inferential statistics (repeated measures ANOVA and Bonferroni post hoc test) were used to examine the research hypotheses regarding the effect of intervention on different pain intensities and WOMAC changes. Before performing statistical analyzes, the normality of data distribution was checked by calculating kurtosis and skewness, which due to the normal distribution, parametric tests were used. Significance level of all tests was considered as P<0.05. Effect size was calculated to measure the level of oil effect.

Results
The mean age of participants was 78±7.79 years (ranged 63-94 years). There were 19 women and 15 men in the intervention group and 16 women and 11 men in the control group. Most participants were illiterate or only able to read and write; had at least one chronic illness, and used at least one medication. There was no significant difference between the intervention and control groups at baseline in terms of age, education, marital status, employment status, smoking, level of physical activity, chronic illness, and medication use.
Right knee pain (F 1,58 =439.70, P<0.001) and left knee pain (F 1,58 =368.8, P<0.001) in both intervention and control groups significantly decreased from the first to the third stage of the study. Moreover, right knee pain intensity (F 2,58 =62.6, P<0.001) and left knee pain intensity (F 2,58 =85.1, P<0.001) in both groups significantly decreased from the first to the third stage of the study. Furthermore, the mean joint stiffness (F 2,58 =69.9, P<0.001) in both groups significantly decreased from the first to the third stage of the study. For all variables of pain, pain intensity and joint stiffness, considering the effect size, the amount of changes from the first to the third stage was higher in the intervention group. The results of Bonfrroni post hoc test showed that the difference between the first and second stages and between the first and third stages of the study were significant in both groups, while the difference between the second and third stages were significant only in the intervention group which may be due to the role of maintenance or the medication used in the intervention group.

Conclusion
The use of melilotus officinalis oil as a cheap, available and uncomplicated treatment on the extent and severity of knee pain and joint stiffness in the elderlies with mild to moderate KO is recommended. Further studies are recommended to investigate the mechanism of the effect of melilotus officinalis oil in reducing knee pain and joint stiffness in elderlies with mild to moderate KO and to determine the exact dose for its use.

Compliance with ethical guidelines
All ethical principles were considered in this article. The participants were informed about the purpose of the research and its implementation stages; they were also as-O sured about the confidentiality of their information; Moreover, They were allowed to leave the study whenever they wish, and if desired, the results of the research would be available to them.

Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-forprofit sectors.

Authors' contributions
All authors contributed equally in preparing all parts of the research.

Conflicts of interest
The authors declared no conflict of interest.