Knee osteoarthritis is a prevalent degenerative joint disorder characterized by chronic knee pain, stiffness, reduced range of motion, and limitations in daily functional activities. Exercise therapy is widely recommended as a first-line conservative approach to reduce symptoms and improve physical performance; however, a substantial proportion of patients continue to experience persistent pain and functional impairment despite adherence to exercise-based rehabilitation.

Carbon dioxide (CO2) infrared laser moxibustion is a non-invasive far-infrared thermal stimulation modality intended to reproduce the localized heating effects of traditional moxibustion without smoke or odor. It is hypothesized to enhance local microcirculation, support tissue oxygenation, and modulate inflammatory activity, thereby contributing to symptom relief and improved joint function. This double-blind, parallel-group randomized controlled trial will evaluate whether adding carbon dioxide (CO2) infrared laser moxibustion to a standardized knee osteoarthritis exercise program provides greater improvement than exercise alone. Eligible participants with radiographic knee osteoarthritis will be randomly allocated to either (1) an exercise-only program or (2) the same exercise program plus carbon dioxide (CO2) infrared laser moxibustion delivered over an 8-week treatment phase (24 sessions). Outcomes will be measured at baseline and at follow-up visits at Month 3 and Month 6 to determine changes in pain intensity measured by the Numerical Pain Rating Scale (NPRS), knee range of motion measured by goniometry, articular cartilage thickness measured by magnetic resonance imaging (MRI), and biochemical markers including bone alkaline phosphatase (BAP) and serum calcium.

This study is a double-blind, parallel-group randomized controlled trial examining the effectiveness of carbon dioxide (CO2) infrared laser moxibustion as an adjunct to exercise therapy in individuals with knee osteoarthritis. Knee osteoarthritis is a multifactorial degenerative condition involving mechanical stress, low-grade inflammation, and progressive joint tissue changes that contribute to pain, restricted movement, and functional limitations. Exercise therapy represents a core component of conservative management; however, residual symptoms are frequently reported, supporting the evaluation of additional non-pharmacological approaches.

Carbon dioxide (CO2) infrared laser moxibustion is a non-invasive modality that delivers far-infrared thermal stimulation to predefined knee-related treatment points, intended to reproduce the therapeutic effects of traditional moxibustion without smoke exposure. Proposed mechanisms include enhancement of local microcirculation, modulation of inflammatory activity, neuromodulatory analgesic effects, and potential support of local tissue metabolism. Participants with radiographic knee osteoarthritis will be allocated to either a standardized exercise program alone or the same exercise program combined with carbon dioxide (CO2) infrared laser moxibustion delivered during an 8-week treatment period.

Participants will be assessed at baseline, at the end of the 8-week intervention period, and during follow-up visits at Month 3 and Month 6 to evaluate short-term and medium-term changes in pain and knee-related outcomes. The findings of this study will contribute to the evidence base for rehabilitation strategies in knee osteoarthritis and inform the potential role of carbon dioxide (CO2) infrared laser moxibustion as an adjunct conservative intervention.

Inclusion Criteria

Adults aged 55 to 65 years, male or female. Diagnosis of knee osteoarthritis with radiographic evidence (Kellgren-Lawrence grade 2 or higher).

Knee osteoarthritis grade II or III according to the American Rheumatism Association (ARA) classification criteria.

History of moderate to severe knee pain on most days during the past month. Able and willing to provide written informed consent and comply with study procedures.

Exclusion Criteria

Other diseases affecting the knee, such as rheumatoid arthritis, ankylosing spondylitis, fibromyalgia syndrome, or chronic fatigue syndrome.

Use of steroid medication or acupuncture or moxibustion treatment within the previous 3 months.

Intra-articular hyaluronate injection within the previous 6 months. Arthrocentesis or arthroscopy within the previous 1 year. Knee or hip replacement surgery, or planned joint replacement surgery during the trial period.

Use of other external treatments during the trial (e.g., topical medication for knee pain).

Body mass index (BMI) greater than 30 kg/m². Lower-limb fracture or injury affecting function. Neurological disorders or nerve root compression affecting the lower limb.

IPD will not be shared because the study involves identifiable clinical and imaging data collected at local hospital sites, and there is currently no institutional infrastructure or approved data-sharing agreement for external distribution. De-identified data may be made available upon reasonable request to the corresponding investigator, subject to ethics approval and institutional policies.

Participants and outcome assessors will be blinded to group assignment throughout the study. Allocation will be concealed from the assessor responsible for baseline and follow-up measurements. Due to the nature of the intervention, the treating personnel delivering carbon dioxide (CO2) infrared laser moxibustion cannot be blinded. Data entry and statistical analysis will be performed using coded group labels to minimize bias.