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.
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.
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).
Parallel
single-leg 20° squat training
BehavioralBoth 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.
regular training
BehavioralIn 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.
Knee joint kinetics during walking
The moment generated at the knee joint during walking.
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.
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.
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.
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.
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).
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