This randomized, assessor-blinded, parallel-group controlled trial will compare the effectiveness and safety of thread-embedding acupuncture versus electroacupuncture in patients with primary knee osteoarthritis. Eligible participants will be adults aged 38 years or older diagnosed with primary knee osteoarthritis according to the 1986 American College of Rheumatology criteria, with chronic knee pain lasting more than 6 months and baseline pain intensity of at least 5 points on the Visual Analog Scale.

A total of 60 participants will be randomly assigned in a 1:1 ratio to receive either thread-embedding acupuncture or electroacupuncture. Both groups will receive the same background standard care, including lifestyle advice and therapeutic ultrasound. The intervention period will last 4 weeks. The primary outcome will be change in total Western Ontario and McMaster Universities Osteoarthritis Index score. Secondary outcomes will include pain intensity measured by the Visual Analog Scale, WOMAC subscale scores, Patient Global Impression of Change, treatment satisfaction, rescue analgesic use, and adverse events.

Knee osteoarthritis is a common chronic degenerative joint disorder characterized by pain, stiffness, reduced mobility, and impaired physical function. Non-pharmacological interventions are important in the management of knee osteoarthritis, particularly for patients in whom long-term pharmacological treatment is limited by comorbidities or adverse effects.

Electroacupuncture is an acupuncture technique in which electrical stimulation is applied through inserted acupuncture needles. Thread-embedding acupuncture is a specialized acupuncture-related procedure in which absorbable catgut thread is inserted into acupuncture points to provide prolonged stimulation. Both interventions are used in traditional medicine practice for musculoskeletal pain, but direct comparative evidence between these two approaches in knee osteoarthritis remains limited.

This trial is designed as a randomized, controlled, assessor-blinded, two-arm parallel-group study with balanced allocation. Participants who meet eligibility criteria and provide written informed consent will be randomly allocated to either the thread-embedding acupuncture group or the electroacupuncture group. Outcome assessors will be blinded to treatment assignment. Due to the procedural characteristics of the interventions, blinding of participants and care providers is not feasible.

Participants in both groups will receive standard background care during the 4-week treatment period, consisting of lifestyle modification advice and therapeutic ultrasound. The thread-embedding acupuncture group will receive catgut thread embedding once every 2 weeks for a total of 2 sessions. The electroacupuncture group will receive electroacupuncture 5 sessions per week for 4 weeks, for a total of 20 sessions. Outcomes will be assessed at baseline, Week 2, and Week 4, with patient-reported global improvement and treatment satisfaction assessed at Week 4.

Inclusion Criteria:

• Age 38 years or older.
• Diagnosis of primary knee osteoarthritis according to the 1986 American - College of Rheumatology criteria.
• Chronic knee pain lasting more than 6 months.
• Baseline knee pain intensity of at least 5 points on the Visual Analog Scale.
• No use of nonsteroidal anti-inflammatory drugs within 1 week before study enrollment.
• Willingness to participate in the study and ability to provide written informed consent.

Exclusion Criteria:

• Systemic diseases, including rheumatoid arthritis, hematological disorders such as coagulation disorders or platelet dysfunction, severe cardiovascular disease such as heart failure or unstable angina, systemic infection, malignancy, immunodeficiency, or current use of immunosuppressive medication or anticoagulant medication.
• Acute knee arthritis with swelling or knee joint effusion.
• Peripheral platelet count less than 150,000/mm³.
• Pregnancy or breastfeeding.
• Alcohol abuse or substance dependence.
• Intra-articular corticosteroid or hyaluronic acid injection into the affected knee within 6 months before study enrollment.
• History of knee surgery or knee arthroscopy.
• Signs of knee joint infection, including swelling, heat, redness, and systemic inflammatory response.
• Severe radiographic knee osteoarthritis, Kellgren-Lawrence grade 4.
• History of allergy, anaphylaxis, or contraindication to thread-embedding acupuncture or electroacupuncture according to the Vietnamese Ministry of Health technical guidance for traditional medicine procedures, including acute illness, severe debility, pregnancy, inflammatory or dermatological lesions at the treatment site, or allergy to absorbable thread.

Participants and treating physicians cannot be blinded because the two procedures are visibly and technically different. Outcome assessment will be performed by research staff who do not perform the interventions and are not involved in randomization. The random allocation list will be maintained by an independent statistician and will not be disclosed to the blinded outcome assessors.