The goal of this clinical trial is to compare FSN with oral Nonsteroidal Antiinflammatory Drugs (NSAIDs) in pain relief and improvement in knee function among elder people, the main questions it aims to answer are: Q1: Compared with the positive drug (celecoxib), whether FSN is more or at least as effective for pain relief and improvement in knee function in elder people with knee arthritis. Q2: From the biomechanical point of view, what is the mechanism by which FSN plays a therapeutic role in knee osteoarthritis (KOA)? Participants will: 1. Will be randomly assigned to 2 groups. There will be 30 participants in each group. 2. A group of patients will receive FSN monotherapy, while the other group will receive oral celecoxib and pantoprazole. Each patient will receive a 2-week course of treatment. 3. Visual analogue scale (VAS), WOMAC, knee range of motion (ROM), gait analysis, and musculoskeletal ultrasonography (US) of lower extremity muscles will be assessed during treatment and in the follow-up. Researchers will compare FSN and celecoxib to see if FSN has better, or at least equivalent, efficacy than celecoxib, which is commonly used in clinical practice.