Efficacy of Thread-Embedding Acupuncture Using the Longitudinal Oblique Technique From BL40 Toward BL57 on KOOS Scores and Joint Range of Motion in Knee Osteoarthritis

Knee osteoarthritis is a chronic degenerative joint disease associated with knee pain, stiffness, functional limitation, and reduced quality of life. Although pharmacological and non-pharmacological treatments are available, some patients may experience limitations related to treatment duration, adverse effects, or the need for repeated treatment.

Thread embedding acupuncture is an acupuncture modality in which an absorbable thread, such as polydioxanone (PDO), is inserted into selected acupuncture points to provide prolonged mechanical and biological stimulation. Previous studies have investigated thread embedding acupuncture for knee osteoarthritis using various local acupuncture points. However, the use of a longitudinal oblique technique from BL40 toward BL57 has been limited in previous clinical studies.

This study is designed to evaluate the efficacy of thread embedding acupuncture using a longitudinal oblique technique from BL40 toward BL57 in patients with knee osteoarthritis. The intervention is based on a proposed neurophysiological, neuromuscular, neurovascular, and myofascial rationale involving the posterior aspect of the lower extremity.

This study is a double-blind, randomized controlled trial with a parallel-group design. A total of 44 participants will be recruited and randomly allocated in a 1:1 ratio into two groups using permuted block randomization with a block size of four. The intervention group will receive thread embedding acupuncture, while the control group will receive sham thread embedding acupuncture.

Participants will be men and women aged 51 to 70 years with bilateral knee osteoarthritis diagnosed clinically and radiologically according to the American College of Rheumatology criteria and with Kellgren-Lawrence grade II or III osteoarthritis. Participants must have a Numeric Rating Scale pain score greater than 3 during activity and must be able to complete the KOOS questionnaire.

In the intervention group, polydioxanone (PDO) thread, 26G × 60 mm, will be inserted bilaterally at BL40 using a longitudinal oblique technique directed toward BL57 at an insertion angle of approximately 15 degrees to the skin surface. The procedure will be performed by a physician trainee in medical acupuncture with a minimum competency level of three. Anatomical landmarks in the popliteal region will be identified before insertion, and body mass index and individual anatomical characteristics will be considered as safety factors.

In the control group, a 0.25 × 25 mm acupuncture needle will be inserted bilaterally at BL40 using a similar longitudinal oblique approach at approximately 15 degrees to the skin surface and then immediately withdrawn without thread implantation.

Participants will be evaluated at baseline and at weeks 2, 4, and 8 after the intervention. KOOS will be assessed at baseline and at weeks 2, 4, and 8. Knee ROM, including flexion and extension, will be measured using a goniometer at baseline and at weeks 2 and 8.

The primary clinical outcomes of interest are changes in KOOS and knee ROM following the intervention. Safety will also be monitored, including local pain, bleeding, hematoma, swelling, infection, allergic or inflammatory reactions, and potential neurovascular complications associated with the procedure.

Participants in the control group will be offered actual thread embedding acupuncture after completion of the study.

Inclusion criteria

• Male and female patients aged 51 to 70 years.
• Clinically and radiologically diagnosed with bilateral knee osteoarthritis according to ACR (American College of Rheumatology) criteria.
• Kellgren-Lawrence grade II or III knee osteoarthritis.
• NRS (Numeric Rating Scale) score >3 during activity (activities of daily living or light exercise).
• Body Mass Index (BMI) ≥18.5 kg/m².
• Knee functional limitations assessable via the KOOS.
• Ability to understand and complete the KOOS questionnaire. MMSE score >23 (normal or no significant cognitive impairment).
• Willingness to complete the study and sign the informed consent form.

Exclusion criteria

• History of knee surgery such as total knee replacement, arthroscopy, or ligament reconstruction.
• Inflammatory joint disease or autoimmune conditions (e.g., rheumatoid arthritis, gouty arthritis, spondyloarthritis, or lupus arthritis) assessed via clinical symptoms and/or radiological findings.
• Presence of a tumor, wound, or local infection at the injection site.
• History of peripheral vascular disease, DVT/thromboembolism, aneurysm or pseudoaneurysm, or coagulation/bleeding disorders.
• Presence of a blood disorder or use of blood thinners (combination antiplatelet or anticoagulant therapy) with an INR ≤ 2.0; history of spontaneous bleeding, thrombocytopenia, or coagulation disorders.
• Uncontrolled diabetes mellitus or severe systemic disease with a random blood glucose (RBG) level ≥200 mg/dL (measured via capillary blood using a glucometer).

Random blood glucose (RBG) level ≥200 mg/dL in non-diabetic patients (measured via capillary blood using a glucometer for all study participants).

• History of keloids.
• Routine use of steroids or NSAIDs, or use of topical analgesics prior to therapy and during the study period.
• Not currently receiving intra-articular knee injections (corticosteroids or hyaluronic acid) and has not received them in the last 3 months.
• Presence of a Baker's cyst in the popliteal fossa, identified during physical examination.
• Patients currently undergoing physiotherapy or who have undergone it within the last month.
• Prior receipt of thread-embedding acupuncture therapy in the knee area or at acupuncture points BL40-BL57 within the last 6 months, or other forms of acupuncture within the last 2 weeks.
• History of hypersensitivity or allergic reactions to polydioxanone (PDO) threads or procedure needle materials (e.g., stainless steel).