Anterior Cruciate Ligament (ACL) is the main stabilizing structure in the knee for preventing the anterior translation of the tibia.

It works in conjunction with the posterior cruciate ligament (PCL) which cross-connects the femur and tibia to stabilize the knee.

Excessive rotation or anterior translation of tibia creates high stress which may injure or even completely tear the ACL. Over 50% of ACL injury is combined with a meniscal injury.

Self File | 前十字韌帶創傷 Anterior Cruciate Ligament Injury (ACL injury)_膝痛成因物理治療



The common injury mechanism is sudden twisting in the knee slightly bent and weight-bearing position or being collided in front of the thigh or the back of the lower leg.


Furthermore, sudden stop or jumping from high distances may also cause ACL injury as the lower leg need to slightly bend to disperse external force. If the quadriceps use large force at this moment, there will be an excessive anterior translation of the tibia, causing ACL injury.

Self File | Anterior Cruciate Ligament Injury (ACL injury) 前十字韌帶創傷_Knee Pain Causes, Physiotherapy Treatment1



Risk Factors

Sports like rugby, basketball, or football, which require a lot of lower limb turning may increase the injury risk.



Common Symptoms
  • “POP” sound of ligament tear will be heard during injury
  • Injured site will have pain and increase in temperature while swelling and redness usually occur after a few hours of injury
  • Knee instability when quick turning or sudden stop
  • May experience limited knee movement in end range

Self File | Anterior Cruciate Ligament Injury (ACL injury) 前十字韌帶創傷_Knee Pain Causes, Physiotherapy Treatment2




Whether ACL reconstruction is needed depends on the severity of the injury and the need for work and sports. If the knee instability severely affects the patient daily life, or if the patient is a professional athlete in contact sports, ACL reconstruction may help to improve knee stability.

However, a very detailed rehabilitation plan after the surgery is essential for returning to sports.


Apart from electrophysical modalities, acupuncture, and scar management, post-surgical rehabilitation can be divided into four stages:


The first stage ( 1-2 weeks post-operation)

  • Patient can do RICE: Rest, Ice, Compression and Elevation
  • Practice walking normally with less support from walking aids
  • Light Hamstrings strengthening exercise
  • Restrict active knee pain-free range from 40-90 degree


The Second Stage (2-6 weeks post-operation)

  • Walk unaided normally
  • Gradually progress the hamstring and quadriceps active stretching in full range
  • Start Close Kinetic Chain (CKC) strengthening exercise, but need to restrict the knee flexion angle according to the progress


The Third Stage (6-10 weeks post-operation)

  • Gradually progress the strengthening exercise in a weight-bearing position, especially for hamstrings
  • Involve knee stability and balance training on unstable surfaces (eg: wobble disc/trampoline)
  • Incorporates cycling, stairs, or aquatic exercise


The Fourth Stage (10 weeks post-operation)

  • Running training in a straight line and multi-angle, for endurance training first followed by speed
  • Progressively includes agility training, such as quick turning, sideways hopping, shuttle run, trampoline, and figure of eight exercise

Self File | 前十字韌帶創傷 Anterior Cruciate Ligament Injury (ACL injury)_膝痛成因物理治療運動1

Self File | 前十字韌帶創傷 Anterior Cruciate Ligament Injury (ACL injury)_膝痛成因物理治療運動2

Self File | 前十字韌帶創傷 Anterior Cruciate Ligament Injury (ACL injury)_膝痛成因物理治療運動3



Preventive Measures

Motor control training and posture correction aiming to improve lower limb biomechanics are important. Sports taping, knee strengthening, and agility training can improve knee stability and reduce injury rates.





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