Medhi 2009.

Methods	Randomised, double‐blind, active control, 2 parallel groups. Duration 4 weeks
Participants	Randomised n=110; intervention n=55, control n=55. Completed n=100; intervention n=50, control n=50. Age 40+ years. OA knee (not ACR criteria), knee pain, knee swelling
Interventions	Tradename not provided. Ricinus officinalis. Castor oil, 2.7ml (3 x 0.9ml), capsule Active control: diclofenac sodium, 150mg (3 x 50mg), capsule Concurrent intervention permitted: all participants encouraged to have physiotherapy
Outcomes	Pain VAS 0‐100
Notes	Exploratory study design; power, effect, and sample size not determined a priori. Reported ethics committee approval. Results favour diclofenac over castor oil for improvement in osteoarthritic knee pain. Pain improved in both intervention and active control groups, but improvement was greater in the diclofenac group.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Described as randomised, method not reported
Allocation concealment (selection bias)	Unclear risk	Allocation concealment not reported. Participants "selected from outpatients" may imply that allocation was unconcealed, or that participation in the study was not voluntary (unclear risk)
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Described as double‐blind, method incompletely reported. Assume active intervention and placebo not distinguished by look, taste, smell or packaging
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Reported withdrawals (low risk) Per‐protocol analysis only (unclear risk) Five participants withdrew due to "efficacy failure", which may confound results
Selective reporting (reporting bias)	Unclear risk	Clinical outcome data reported as percentages and P values only, insufficient for extraction (unclear risk) Reported adverse events (low risk)
Other bias	Unclear risk	Diagnosis / assessment not consistent with ACR criteria (unclear risk)