Efficacy of Extracts of Oleogum Resin of Boswellia in the Treatment of Knee Osteoarthritis: A Systematic Review and Meta-Analysis

Abstract

Knee osteoarthritis (OA) has recently been ranked as the 11th highest contributor to global disability. More than 40% of patients use complementary and alternative medicine including supplements containing phytoextracts with anti-inflammatory properties as those from the Boswellia genus. The aim of this meta-analysis was to evaluate the efficacy of phytoextracts from the oleogum resin of the Boswellia genus as supplementation for patients affected by knee OA. Four electronic databases were used for the research and PRISMA statements were followed throughout the study. The following inclusion criteria were used: (a) the subjects of the study were humans with a diagnosis of knee OA reported by medical staff; (b) randomization and the presence of control (placebo, negative or positive control), and (c) outcomes reported with WOMAC and/or visual analog scale (VAS) score. Publication bias was assessed with a funnel plot and through the Egger test. The Jadad scale was used in order to assess the quality of the studies included. The statistical heterogeneity was assessed using I² statistics. Results of meta-analysis and subgroup analysis were reported using a forest plot. A total of 13 studies involving 850 (WOMAC) and 1185 (VAS) patients met the inclusion criteria. The meta-analysis did not detect a significant effect of the use of Boswellia extracts between the control and the treatment groups due to the high heterogeneity of the studies (p = 0.0865 for WOMAC) and (p = 0.3966 VAS). However, the subsequent subgroup analysis demonstrated the significant beneficial effect of Boswellia extracts in the treatment of knee OA with respect to a placebo (lower WOMAC score in the treatment groups). This was also confirmed in the meta-regression applied to the WOMAC scores. This is an important finding as people exposed to NSAID-related adverse effects could benefit from the use of Boswellia extracts. However, further high-quality studies are needed to establish the clinical efficacy of extracts from the genus Boswellia.

Keywords: Boswellia extract; anti‐inflammatory phytoextracts; complementary and alternative medicine; frankincense; knee; osteoarthritis.

FIGURE 1

Rob 2 analysis of the WOMAC score.

FIGURE 2

Rob 2 analysis of the VAS score.

FIGURE 3

PRISMA flowchart of the study selection process.

FIGURE 4

Funnel plot for the WOMAC score (Egger test p = 0.0603). The numbers refer to the respective references.

FIGURE 5

Funnel plot for the VAS score (Egger test p = 0.0589). The numbers refer to the respective references.

FIGURE 6

Efficacy of Boswellia extracts in the management of knee OA: A forest plot of the outcome of the meta‐analysis for WOMAC score between control and treatment groups in a standardized mean difference meta‐analysis (SMD = −0.24, 95% CI = −0.51 to 0.03).

FIGURE 7

Efficacy of Boswellia extracts in the management of knee OA: A forest plot of the WOMAC score subgroup analysis based on the control type.

FIGURE 8

Efficacy of Boswellia extracts in the management of knee OA: A forest plot of the WOMAC score subgroup analysis based on the treatment type.

FIGURE 9

Efficacy of Boswellia extracts in the management of knee OA: A forest plot of the WOMAC score subgroup analysis based on the duration of the studies including different time points.

FIGURE 10

Efficacy of Boswellia extracts in the management of knee OA: A forest plot of the VAS score between the control and the treatment groups in an SMD meta‐analysis.

FIGURE 11

Efficacy of Boswellia extracts in the management of knee OA: A forest plot of the VAS score subgroup analysis based on control type.

FIGURE 12

Efficacy of Boswellia extracts in the management of knee OA: A forest plot of the VAS score subgroup analysis based on the treatment type.

FIGURE 13

Efficacy of Boswellia extracts in the management of knee OA: A forest plot of the VAS score subgroup analysis based on the duration of the studies.