Knee Ligament Injury: Anterior Cruciate Ligament (ACL)

on June 30, 2020


Anterior Cruciate Ligament (ACL) is one of four ligaments that are critical to the stability of the knee joint. An ACL injury is a tear or sprain of the anterior cruciate (KROO-she-ate) ligament. Of the four ligaments of the knee, an ACL injury or rupture is one of the more debilitating knee ligament injuries. See figure 1. ACL injuries most commonly involve sudden stops or changes in direction, jumping and landing such as:    

  • Landing from a jump with foot plant outwards and the knee caving inward
  • Landing on the buttocks with knee caved in (valgus position)
  • Contact ACL: Occurs mostly when you’re being hit, touched by an opponent or teammate. e.g.: when a football striker gets tackled in the knee (from outwards in) by a defender of an opponent team.

Many people hear or feel a “pop” in the knee when an ACL injury occurs. Most of the common symptoms are swelling on your knee, loss of motion, anterior translation of the tibia, feeling unstable and pain upon weight bearing if the tear is serious. Depending on the severity of your ACL injury, treatment may range from rest and rehabilitation exercises to help you regain strength and stability, to surgery to replace the torn ligament followed by rehabilitation.

We, at Rehamed Therapy, are able to provide physiotherapy and rehabilitation services if you have suffered an ACL injury with our state-of-the-art facilities and world class physios. We also have injury prevention programs that help lower the risk of an ACL injury or re-injury. We are more than confident to assist you with your rehabilitation and road to recovery should you have suffered an ACL Injury.

Figure 1


Function of ACL

 The Anterior Cruciate Ligament (ACL) is to restrict the anterior translation of the shin bone (tibia). The femur (thigh bone) sits on top of the tibia, and the knee joint allows movement at the junction of these bones. During rotation of the knee joint, the ACL also plays a role in providing stability.

The mechanisms of injury are typically a sudden deceleration or rotational maneuver with a force that sends the tibia one way and femur another (for example, because the foot is planted and the body spins; see Figure 2).

Not all such forces that exceed the strength of the ligament lead to a tear: often, the secondary restraints (such as the hamstrings) can help resist a tear. When the secondary restraints are overwhelmed, the ligament can be exposed to forces it cannot bear.

Why would the hamstrings be overwhelmed? Well, for one thing, the knee may be extending at the very second of injury, a phase of motion where the hamstrings do not fire; alternatively, they could be too tired. For example, at the start of an exercise session or sport, your still-powerful hamstrings protect the ACL. Toward the end of said strenuous exercise session or sport, the hamstrings experience neuromuscular fatigue. Once that occurs, the recruitment of neuromuscular units of the hamstring is compromised, thus the hamstring may be unable to protect the ACL.

An ACL tear is suspected first by history. A “pop” heard by the patient, immediate pain and swelling after a twist are typical features. To test for an ACL tear on a physical exam, one can use the anterior drawer and Lachman tests. The Lachman test is more preferred because the angle at which it is done (20°-30°) inhibits the hamstrings from contracting, thus minimizing the risk of a false negative.

The Lachman test is performed by attempting to produce an anterior translation of the tibia. An intact ACL limits anterior translation and provides a distinct endpoint. Increased translation compared to the uninjured knee and a vague endpoint suggest an ACL injury.

Figure 2


What happens to a Partial Tear ACL?

A partial tear can be tested through a physical examination by a doctor or physiotherapist, with an MRI to confirm the findings. If the ACL is partially torn, and the other structures are still intact, surgery is not needed but physiotherapy and rehabilitation are essential to provide stability of the knee. The primary focus will be strengthening the hamstring as this muscle will prevent the shin bone (tibia) to move anteriorly. Typically, when working with patients with this injury, the process of rehabilitation is not long provided the patient is consistent. However, upon discharge, the patient is still advised to maintain the exercises prescribed as a home program.

What happens if you choose to do Nothing?

A partial tear of the ACL is not always a serious matter, but if you choose to ignore and continue playing sports, then the tear can worsen and start to affect the other structures in the knee joint, primarily the meniscus. As the tear gets worse and potentially ruptures, knee surgery is needed to reconstruct the torn ACL. Below are a few steps that can be treated without a surgery by visiting a our center:

  • First, physiotherapy needs to reduce pain and swelling if present on the knee (thermal application)
  • Sometimes fluid accumulation surrounds the knee joint, and manual work such as effleurage is required to help flush out the fluid
  • Electrotherapeutic modalities like ultrasound
  • Range of motion exercises to improve range at joint
  • Active assisted/passive knee flexion and extension
  • Progressive strengthening exercises
  • Active rehabilitation program based on sports therapy principles


What happens to a Ruptured(total tear) ACL?

A ruptured ACL is a total tear creating instability of the knee. This causes the shin bone to move forward and the patient feels the knee is loose. A rupture of the ACL will usually affect the knee to rely on the meniscus for additional support (see figure 3); this may end up causing damage to the meniscus due to excessive load-bearing.

 Figure 3

What happens if you choose to ignore a ruptured ACL injury?

When the ACL is ruptured, if treated through surgery, the rehab is straightforward and return to sport can be successfully treated within 6-8 months for professional athletes. However, if the injury is not treated, the ACL will (as mentioned above) depend on the meniscus for additional support which causes the meniscus to injure. This may significantly increase the eventual medical bill as repairing an injured meniscus can be an expensive procedure. Additionally, if continued to be left untreated, there will be further damage to the cartilage which will then lead to osteoarthritis.

After Surgery of ACL Reconstruction:

Should surgery be required, immediate physiotherapy and rehabilitation is the most important process for recovery. This is when both physiotherapists and sports therapists need to work hand in hand to achieve the best post-surgery result.

Outlined below is a timeline for a post-surgery ACL rehabilitation program:

Week 1-4 (focus on physiotherapy)

  • Regular icing and elevation are used to reduce swelling. The goal is full extension and 70 degrees (this may depend on the recommendation of the operating doctor’s recommendation) of flexion by the end of the first week. The use of a knee brace and crutches are imperative.
  • Multidirectional mobilizations of the patella should be included for at least 8 weeks. Other mobilization exercises in the first 4 weeks are a passive extension of the knee (no hyperextension) and passive and active mobilization towards flexion. Strengthening exercises for the calf muscle, hamstring, and quadriceps (vastus medialis) can be performed.

Week 3-4 (initial sports therapy)

  • The patient must learn to walk with partial weight-bearing, assisted by a crutch, in order to avoid the loss of gait muscle memory. With good hamstring/quadriceps control, the use of crutches can be reduced sooner.

Week 5 (physiotherapy and sports therapy)

  • The use of the knee brace is progressively reduced. Passive mobilization for knee flexion closed chain exercises should be built from less responsible positions (bike, leg presses, step). The progress of the exercise depends on pain, swelling and quadriceps control.
  • Proprioception and coordination exercises can start if the general strength is good. This includes balance exercises on balance/wobble boards, SRT, mats, etc.

Week 10 (sports therapy accompanied by physiotherapy)

  • Forward, backward, and lateral dynamic movements can be included on top of strengthening exercises.

 Week 10 – 15 (focus on sports therapy)

  • After 3 months, patients can move on to functional exercises (confidently, being the keyword) such as running and jumping. As proprioceptive and coordination exercises become more taxing and complex, quicker changes in direction are possible.
  • To stimulate coordination and control through afferent and efferent information processing, exercises should be enhanced by variation in visible input, surface stability (g., trampoline), speed of exercise performance, the complexity of the task, resistance, one or two-legged performance.

Week 16 – 25 (focus on sports therapy)

  • The final goal is to maximize endurance and strength of the knee stabilizers, optimize neuromuscular control with plyometric exercises, and to add the sport-specific exercises. Acceleration and deceleration, variations in running and turning and cutting manoeuvers improve autokinetic reflexes to prevent new trauma during competition.

However, it should be noted that the above all will depend on the individual’s condition throughout and close coordination with the treating doctor regarding the patient’s capabilities and their treatment program will be undertaken.


Take home message:

The idea behind treatment for a partial or total ACL tear is to treat the injury as soon as possible. Leaving the injury for a prolonged period of time will cause other structures of the knee to be damaged, worsening the overall condition of the knee.

If you want to know more about the types of exercises and stretches that can be done, feel free to give us a call at 03-50315946 or send us a Whatsapp or Make an Appointment. We at Rehamed Therapy are always here to help!



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