To investigate the clinical outcomes of arthroscopic anatomical repair of the posterolateral bundle (PLB) of the anterior cruciate ligament (ACL) combined with cosmetic portal suturing for the treatment of mild anterior knee instability.

Twenty-one patients with mild anterior knee instability underwent arthroscopic anatomical repair of the PLB of ACL. Cosmetic suturing was simultaneously performed for the anteromedial and anterolateral portals. The patients underwent a standard rehabilitation protocol and were followed up for one to six months after surgery. Knee stability was evaluated by Lachman test, anterior drawer test (ADT), and pivot-shift test. MRI findings, and functional assessments—including the International Knee Documentation Committee (IKDC) subjective evaluation form, Lysholm knee scoring scale, and Tegner activity score—were compared between the data before surgery and data during the follow-up. Incision healing and complications were also recorded. The data were analysed by repeated variation analysis and rank sum test.

Among the 21 patients, 19 achieved full range of knee motion eight weeks after surgery, while two experienced restricted knee flexion at 90°. Knee stability: compared with preoperative grade Ⅱ positive Lachman tests, all the patients demonstrated negative Lachman tests postoperatively. The ADT and pivot-shift test remained negative. Postoperative MRI revealed uniform and continuous ACL signals across two consecutive slices, indicating significantly improved ligament tension. Functional assessment: IKDC, Lysholm, and Tegner scores after surgery were significantly higher than the preoperative values (F=55.99, 105.84, Z=37.86, all P<0.001). Incision healing: no infections or other adverse events occurred in any of the patients. One patient with a scar diathesis developed scar induration, hyperpigmentation, and localized pain during extreme knee flexion. The remaining patients achieved excellent incision healing.

Arthroscopic anatomical repair of the ACL PLB combined with cosmetic portal suturing for mild anterior knee instability can effectively minimize incision-related irritation and facilitate the early rehabilitation of knee function. Long-term outcomes warrant a further follow-up observation.