Study aim: Investigating the Effect of a Topical Chamomile Preparation on Pain Reduction and Functional Improvement in Patients with Knee Osteoarthritis Compared with Diclofenac Gel Design: This study is a randomized, controlled, double-blind, parallel-group clinical trial involving 72 patients with primary knee osteoarthritis. Participants will be allocated at a 1:1 ratio to either the intervention group or the control group. Individual participants will be randomized using block randomization, and the allocation sequence will be generated using randomization software. Settings and conduct: This study will be conducted as a randomized, controlled, double-blind, parallel-group clinical trial involving 72 patients with primary knee osteoarthritis at the clinics affiliated with Babol University of Medical Sciences. Participants/Inclusion and exclusion criteria: Inclusion criteria: include a clinical diagnosis of primary knee osteoarthritis, knee pain, radiographic evidence of osteophytes, age ≥50 years, morning knee stiffness lasting less than 30 minutes, knee crepitus during movement, Participants with grade 1 to 3 osteophyte severity based on the Kellgren–Lawrence classification on knee radiographs, and participants with a pain intensity score of ≥3 and ≤8 on the Visual Analog Scale. Exclusion criteria: include severe osteoarthritis, limited mobility, and the absence evidence of osteoarthritis. Intervention groups: Participants in the intervention group will receive the topical chamomile preparation, while those in the control group will receive 1% diclofenac gel, with both treatments applied as one fingertip unit to the affected knee every 8 hours throughout the study period. Main outcome variables: The study outcomes will include joint pain, joint stiffness, physical activity, quality of life, osteophyte severity, and treatment duration.