This multicenter, stratified, partially randomized clinical trial aims to compare autologous semitendinosus tendon graft and meniscal allograft transplantation (MAT) in young adults with post-meniscectomy syndrome. The meniscus plays a critical role in load distribution, shock absorption, and joint stability. After meniscectomy, insufficient meniscal tissue often leads to persistent pain, swelling, and functional decline, increasing the risk of early osteoarthritis.

Two reconstructive strategies are clinically available: MAT provides immediate biomechanical function but requires donor matching and carries higher costs, while autologous tendon graft offers stable supply and no immunologic risk but lacks long-term clinical validation.

In this study, 40 patients aged 18-45 years will be enrolled. Participants will be allocated into four groups (randomized MAT, randomized autograft, patient-preference MAT, patient-preference autograft). All procedures will use a two-tunnel fixation technique with additional internal brace support.

The primary endpoint is the improvement in KOOS (Knee Injury and Osteoarthritis Outcome Score) at 24 months postoperatively. Secondary endpoints include MRI-based assessment of graft morphology and extrusion, reoperation rate, complications, patient satisfaction, and return-to-sport time.

This trial will provide critical evidence regarding the comparative effectiveness and feasibility of tendon autograft versus meniscal allograft in real-world clinical settings, potentially informing surgical decision-making and future treatment guidelines for post-meniscectomy syndrome.

Post-meniscectomy syndrome represents a challenging condition in young adults, characterized by persistent pain, swelling, and functional impairment after partial or subtotal meniscectomy. The lack of sufficient meniscal tissue predisposes patients to abnormal tibiofemoral loading and early onset osteoarthritis. Current reconstructive options remain limited, and there is no consensus on the optimal surgical strategy.

Meniscal allograft transplantation (MAT) has been the most widely accepted method, offering immediate restoration of meniscal morphology and load-distributing capacity. However, MAT is constrained by donor availability, graft costs, and local regulations. In contrast, autologous tendon grafts-most commonly using semitendinosus-are readily available, carry no risk of rejection, and reduce cost barriers. Early biomechanical and translational studies suggest that autologous tendon grafts may adapt to meniscal-like properties, yet long-term clinical data remain scarce.

This trial employs a stratified, partially randomized design to balance methodological rigor with patient autonomy and ethical feasibility. Participants are assigned to autologous tendon graft or MAT either through randomization or patient preference, allowing assessment of outcomes under both controlled and real-world conditions. All procedures are standardized across participating centers, utilizing a two-tunnel fixation technique and augmented with an internal brace (Fibertape) to enhance graft stability.

Outcomes will be assessed over 24 months, including validated patient-reported measures (KOOS, IKDC, Tegner), MRI-based graft evaluation (volume, signal, extrusion, morphology), reoperation rates, complications, satisfaction, and return-to-sport. By integrating randomized comparison with pragmatic elements, this study aims to generate clinically applicable evidence on the relative benefits and limitations of autologous tendon graft versus MAT. The findings are expected to inform surgical decision-making, optimize patient outcomes, and guide future treatment recommendations for young patients suffering from post-meniscectomy syndrome.

Inclusion Criteria:

• Adults aged 18 to 45 years

History of partial meniscectomy > 6 months prior to enrollment

Symptomatic post-meniscectomy syndrome (knee pain, swelling, or functional decline)

MRI showing cartilage status ≤ Outerbridge grade 2

Knee joint stability (or stabilized during the index surgery)

Body mass index (BMI) < 30

Willingness to provide written informed consent

Exclusion Criteria:

Tibial slope > 16°

Radiographic or arthroscopic evidence of advanced cartilage degeneration (Outerbridge > 2 or ICRS ≥ 3)

Presence of inflammatory arthritis or systemic inflammatory joint disease

History of cartilage repair surgery

Malalignment > 5° not corrected

Untreated ligamentous instability

Any other condition judged by the investigator to compromise study participation or outcomes

1. Protection of participant privacy and confidentiality is paramount in this study involving sensitive medical data and procedures. Sharing identifiable IPD could breach the trust and privacy of these patients undergoing knee surgeries.
2. The informed consent process likely did not explicitly state or obtain approval from participants to share their individual-level data, including medical images, functional assessments, and clinical outcomes, with third parties outside the research team.

Postoperative MRI and patient-reported outcome measures (PROMs) will be evaluated by independent assessors blinded to treatment allocation. Participants, surgeons, and investigators will be aware of the intervention due to the surgical nature of the study.