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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
48
Both groups underwent conventional training. In addition, the experimental group underwent single-leg 20° squat training. Participants were required to stand for the exercise and hold onto a stable surface with their hands, while the unaffected lower limb hip joint was extended and the knee joint flexed to 90°. Participants were then instructed to bend the affected knee to 20° and hold this position for 10 seconds. They then fully extended the knee and rested in that position for 3-4 seconds. The load form can be dumbbells.
In the 1-8 week rehabilitation program, the goal is to strengthen the muscle strength of the affected knee joint and gradually introduce functional movement exercises, while avoiding forceful flexion and extension of the knee. The specific rehabilitation program includes: prone leg curl exercises, quadriceps resistance band training, hamstring progressive resistance exercises, backward lunge exercises, in-place small jumps, knee joint flexion with appropriate cushioning, in-place squat jumps, landing and immediately squatting for stability, repeated 15 times, each lasting 2-3 seconds, performed 2-3 sets per week, totaling 3 sessions; Wall-supported static squat exercises, repeated 5 times, performed 2-3 sets per week, totaling 3 sessions.
Knee joint kinematics during walking
Kinematic angles (flexion, rotation, and adduction) of the knee joint in the sagittal, frontal, and horizontal planes during walking.
Time frame: Assessed at 12 weeks post-operation and again after 8 weeks of intervention (total assessment period of 2 months）
Knee joint kinetics during walking
The moment generated at the knee joint during walking.
Time frame: Assessed at 12 weeks post-operation and again after 8 weeks of intervention (total assessment period of 2 months)]
Gait-Synchronized Electromyographic Signals
Outcome Measure 1: Raw electromyographic (EMG) activity Raw EMG signals of the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, and semitendinosus muscles during specified movements. Outcome Measure 2: Integrated electromyographic (IEMG) activity The integrated EMG (IEMG) of the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, and semitendinosus muscles during specified movements. Outcome Measure 3: Average electromyographic (AEMG) amplitude The average EMG amplitude (AEMG) of the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, and semitendinosus muscles during specified movements.
Time frame: Assessed at 12 weeks post-operation and again after 8 weeks of intervention (total assessment period of 2 months)]
Isokinetic muscle strength
Quadriceps isokinetic strength test: Isokinetic biomechanical test and trainer (CON-TREX, MJ; Germany), conducted by the same tester on a constant velocity device. Three complete movements need to be collected, with an interval of 90 seconds between each test to avoid fatigue. The quadriceps muscle was tested for isokinetic and eccentric peak torque (PT) at 60°/s.
Time frame: Assessed at 12 weeks post-operation and again after 8 weeks of intervention (total assessment period of 2 months)
Anterior cruciate ligament stress distribution and peak.
* Joint flexion, rotation and adduction angles of the knee joint in the sagittal, frontal and horizontal planes during walking and squatting at 20°. * measured during squatting at 12 weeks post-anterior cruciate ligament reconstruction surgery. Stress and strain distribution in the anterior cruciate ligament at a 20-degree squat angle were calculated using ANSYS.
Time frame: Completed through study, averaging 3 months.
Anterior cruciate ligament stress distribution and peak.
* the moment generated during movement, and the tibial displacement during squats at 20°. * measured during squatting at 12 weeks post-anterior cruciate ligament reconstruction surgery. Stress and strain distribution in the anterior cruciate ligament at a 20-degree squat angle were calculated using ANSYS.
Time frame: "through study completion, an average of 3 month".
Lysholm Knee Scoring Scale
The Lysholm Knee Scoring Scale, a patient-reported outcome measure assessing knee function. Scores range from 0 to 100, where higher scores indicate a better outcome.
Time frame: Assessed at 12 weeks post-operation and again after 8 weeks of intervention (total assessment period of 2 months)]
International Knee Documentation Committee Subjective Knee Form
The International Knee Documentation Committee Subjective Knee Form, a patient-reported outcome measure assessing symptoms, function, and sports activity. Scores range from 0 to 100, where higher scores indicate a better outcome.
Time frame: Assessed at 12 weeks post-operation and again after 8 weeks of intervention (total assessment period of 2 months）
Thigh circumference measurement
The circumference of the thigh, measured at a standardized anatomical location, to assess muscle atrophy or swelling. A smaller circumference indicates a worse outcome (greater atrophy or reduced swelling).
Time frame: Assessed at 12 weeks post-operation and again after 8 weeks of intervention (total assessment period of 2 months)
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