Introduction: Fu's Subcutaneous Needling (FSN) is a new type of acupuncture treatment method based on the subcutaneous tissue sweeping technique, and it has been proven to have a good therapeutic effect on ankle sprain. However, at present, the difference between its curative effect and the ankle joint orthosis and exercise therapy recommended by the Guidelines remains unclear. Therefore, this study aims to explore the improvement effects of FSN on pain relief, joint function improvement, and ankle balance ability by comparing with ankle orthosis combined with exercise therapy. Verify whether it is more helpful in preventing the progression of lateral ankle sprain (LAS) to chronic ankle instability (CAI) and provide evidence-based basis for clinical decision-making.

Methods and analysis: This study is a randomized, parallel - controlled, single - center prospective clinical study. This study will include 60 subjects with postacute lateral ankle sprain and divide them into the FSN group and the combined treatment group. There are 30 cases in each group. The FSN group will be treated with Fu's subcutaneous needling three times a week for a total of two weeks. The Combined treatment group will wear ankle orthotics from 9:00 to 20:00, and complete resistance exercise training every day for a total of two weeks.Patients will be followed up for 6 months after the treatment. The main efficacy index is the change value of the Visual Analog Scale (VAS) compared to the baseline after 2 weeks of treatment. The secondary indicators include active range of motion (ROM) of the ankle joint, Star Excursion Balance Test (SEBT), and the Foot and Ankle Ability Measure (FAAM) to prove the clinical efficacy.

Ethics and dissemination: This study strictly adheres to the ethical guidelines of the Declaration of Helsinki.This study has passed the review of the Ethics Committee of Guangdong Provincial Hospital of Chinese Medicine. Approval No.: YF 2025 - 158 - 01. All subjects will sign a written informed consent form. The research results will be publicly published in journals indexed by SCI.

Keywords: Fu's subcutaneous needling, Ankle sprain, Postacute lateral ankle sprain, Chronic ankle instability, Functional rehabilitation, Balance, Non-surgical therapy

Inclusion Criteria:

1. Patients with first-time lateral ankle sprains
2. The patient presents with symptoms of swelling and aching and weakness in the ankle joint. There may be a feeling of friction during joint movement, and the symptoms are aggravated after long - distance walking or on rainy and overcast days.
3. The patient presents with swelling and tenderness in the anteroinferior aspect of the lateral malleolus and the anterolateral aspect of the medial malleolus, and has limited mobility during inversion and flexion-extension.
4. Auxiliary examinations: No fracture or dislocation was found in the patient during the examination, and no fracture was detected by X-ray examination.
5. The patient's sprain time is more than 3 weeks and within 6 months.
6. Those who have not received surgical treatment at other medical institutions before coming to our hospital for treatment, can complete the treatment and accept follow - up.
7. The patients' ages range from 18 to 60 years old.
8. The patient voluntarily and is capable of signing the Informed Consent Form.

Exclusion Criteria:

1. Those with complete rupture of fractures or soft tissues such as muscles, tendons, and ligaments
2. Patients with severe primary diseases such as heart, liver, kidney, hematopoietic system diseases and mental diseases
3. Patients with tumors or tuberculosis in the ankle joint
4. Patients with rheumatic and rheumatoid arthritis, or gout.
5. Patients with acute inflammatory reactions such as redness, swelling, heat and pain and signs of infection in the ankle joint, or those accompanied by severe osteoarthritis.
6. Patients with abnormal coagulation function or bleeding tendency, such as those with thrombocytopenia and severe diabetes.
7. Patients during pregnancy and lactation
8. Patients with damaged skin at the necessary needle insertion sites.

To maximally reduce other potential sources of bias, the intervention operators, outcome assessors, data collectors, and data analysts act as independent researchers. Except for the intervention operators, the researchers should not be aware of the participants' group assignments.