The Effect of Single-leg 20-degree Squats Combined With Conventional Training on the Biomechanical Characteristics of Gait After Anterior Cruciate Ligament Reconstruction Surgery

The Effect of Single-leg 20-degree Squats Combined With Conventional Training on the Biomechanical Characteristics of Gait After Anterior Cruciate Ligament Reconstruction Surgery

Anterior cruciate ligament (ACL) tears are one of the most common sports injuries, with an ACL injury rate as high as 20.9% in the general population . Currently, the primary treatment for ACL tears is arthroscopic reconstruction surgery to restore knee stability and function . Following ACL injury, abnormal gait biomechanical characteristics persist, even after ACL reconstruction surgery (ACLR) and evidence-based rehabilitation therapy. These abnormal gait biomechanical characteristics remain unresolved, with the lower limbs exhibiting insufficient loading and stiffness, which are associated with quadriceps muscle dysfunction. Interventions for quadriceps atrophy following ACLR should be initiated early to prevent worsening of early knee pain, swelling, and abnormal gait. Additionally, since ACL reconstruction results in different biomechanical characteristics at various stages and gait phases, it is important to adopt more targeted and precise rehabilitation measures to correct biomechanical abnormalities and improve gait function in patients.

Research Background: The anterior cruciate ligament (ACL) is one of the important anatomical structures in the knee joint, maintaining knee stability and preventing anterior displacement of the tibia. Following ACL injury, abnormal gait biomechanical characteristics persist, even after ACL reconstruction surgery (ACLR) and evidence-based rehabilitation therapy, with abnormal gait biomechanics failing to fully recover. Quadriceps atrophy is a common cause of abnormal gait biomechanics and persists long-term postoperatively. The quadriceps are closely related to knee joint function and contribute most significantly to knee joint stability and movement control. Therefore, intervention for quadriceps atrophy following ACLR should be initiated early to prevent worsening of early knee pain, swelling, and abnormal gait. Post-ACLR rehabilitation aims to protect the graft, promote its biological remodeling, and limit the extent of muscle atrophy while facilitating muscle strength recovery. Additionally, since ACL injury and reconstruction exhibit different biomechanical characteristics at various stages and gait phases, it is essential to adopt more targeted and precise rehabilitation measures to correct biomechanical abnormalities and improve gait function. Research methods: This study plans to recruit 48 patients 12 weeks post-ACL reconstruction surgery, divided into an experimental group and a control group. The experimental group will undergo single-leg mini squat (SLMS) training in addition to conventional training, with kinematic and dynamic data collected simultaneously using a three-dimensional motion capture system and force plate system; electromyographic signals will be collected from patients during gait testing. Additionally, three-dimensional finite element modeling will be used to calculate the stress distribution and peak stress on the ACL graft during SLMS. Expected Study Outcomes: This study anticipates that after 8 weeks of SLMS training, the knee flexion angle during the stance phase of walking, knee extension torque, and activity of the medial femoral muscle during walking will increase. Additionally, the study aims to confirm that SLMS training keeps stress on the ACL graft within a safe range.

Inclusion Criteria:

• Clinical diagnosis of unilateral Anterior Cruciate Ligament (ACL) rupture.
• Aged between 18 and 45 years.
• Scheduled for primary unilateral ACL reconstruction at our hospital.
• Presence of quadriceps atrophy, defined as the bilateral difference in quadriceps strength is >10% of the contralateral unaffected limb.
• The operated knee has no significant redness, swelling, pain, inflammation, or limitations in range of motion and has essentially restored basic joint mobility.
• No or only minor (Grade I) injury to the posterior cruciate ligament, medial collateral ligament, or lateral collateral ligament.

Exclusion Criteria:

• Severe injury (Grade II or III) to the posterior cruciate ligament, medial collateral ligament, or lateral collateral ligament in the affected knee.
• Concomitant severe meniscal tear(s) in the affected knee.
• History of significant prior trauma or surgery to the affected knee.
• Presence of other knee joint diseases (e.g., osteoarthritis, tumors, rheumatoid arthritis, tuberculosis).
• Poor subject compliance or anticipated inability to complete the entire study protocol.Subject withdrawal of informed consent.
• Any reason the subject proposes to terminate the study or is unable to complete the trial.
• In the investigator's judgment, continued participation would adversely affect the subject's physical condition.
• Decision by the Ethics Review Committee to terminate the study.