Background: Osteoarthritis (OA) is a disabling condition that affects more than one-third of people older than 65 years. Currently, 80% of these patients report movement limitations, 20% are unable to perform major activities of daily living, and approximately 11% require personal care. In 2014, the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO) recommended, as the first step in the pharmacological treatment of knee osteoarthritis, a background therapy with chronic symptomatic slow-acting osteoarthritic drugs such as glucosamine sulfate, chondroitin sulfate, and hyaluronic acid. The latter has been extensively evaluated in clinical trials as intra-articular and oral administration. Recent reviews have shown that studies on oral hyaluronic acid generally measure symptoms using only subjective parameters, such as visual analog scales or quality of life questionnaires. As a result, objective measures are lacking, and data validity is generally impaired., Objective: The main goal of this pilot study with oral hyaluronic acid is to evaluate the feasibility of using objective tools as outcomes to evaluate improvements in knee mobility. We propose ultrasound and range of motion measurements with a goniometer that could objectively correlate changes in joint mobility with pain reduction, as assessed by the visual analog scale. The secondary objective is to collect data to estimate the time and budget for the main double-blind study randomized trial. These data may be quantitative (such as enrollment rate per month, number of screening failures, and new potential outcomes) and qualitative (such as site logistical issues, patient reluctance to enroll, and interpersonal difficulties for investigators)., Methods: This open-label pilot and feasibility study is conducted in an orthopedic clinic (Timisoara, Romania). The study includes male and female participants, aged 50-70 years, who have been diagnosed with symptomatic knee OA and have experienced mild joint discomfort for at least 6 months. Eight patients must be enrolled and treated with Syalox 300 Plus (River Pharma) for 8 weeks. It is a dietary supplement containing high-molecular-weight hyaluronic acid, which has already been marketed in several European countries. Assessments are made at the baseline and final visits., Results: Recruitment and treatment of the 8 patients began on February 15, 2018, and was completed on May 25, 2018. Data analysis was planned to be completed by the end of 2018. The study was funded in February 2019. We expect the results to be published in a peer-reviewed clinical journal in the last quarter of 2024., Conclusions: The data from this pilot study will be used to assess the feasibility of a future randomized clinical trial in OA. In particular, the planned outcomes (eg, ultrasound and range of motion), safety, and quantitative and qualitative data must be evaluated to estimate in advance the time and budget required for the future main study. Finally, the pilot study should provide preliminary information on the efficacy of the investigational product., Trial Registration: ClinicalTrials.gov NCT03421054; https://clinicaltrials.gov/study/NCT03421054., International Registered Report Identifier (irrid): RR1-10.2196/13642., (©Dumitru Emanuel Dogaru, Serban Rosu, Dionisio Franco Barattini, Simone Guadagna, Luca Barattini, Bogdan Andor. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 28.06.2024.)