Anterior cruciate ligament (ACL) sprains are one of the most common sports injuries of the knee, especially in “stop and go” sports. Athletes participating in high load activities like soccer, rugby, hockey or sprinting are more likely to injure their ACL, compared to the general population. The ACL is the strongest and most important ligament in the knee, yet tears of this ligament are quite common, traumatic and need attention straight away.

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ACL stands for anterior cruciate ligament. “Anterior” means front, “cruciate” means shaped like a cross and a “ligament” is a band of tissue connecting bones. It is one of the four ligaments in the knee that assist in stabilising the joint.

The ACL has two main functions: it is mainly responsible for providing stability in the knee joint by preventing forward movement of the shin bone (tibia) on the thigh bone (femur), thus hyperextension. It also helps to prevent excessive twisting.

The ACL originates on the back of the thigh bone and runs forwards and downwards to insert on the front of the shin bone. It is approximately 2 cm long and as thick as a pencil. Together with the posterior cruciate ligament, it forms an “X” inside the knee joint, thus preventing excessive movement.

Although ACL knee injuries are relatively common, most ACL tears happen when there is no impact or contact with another player. It usually occurs if the knee twists when landing from a jump. The pressure from your body weight and the angle of pull on the ligament pushes it beyond its normal limits causing a ligament sprain or tear.

For example, you play a rugby match and your teammate pass you the ball. The defender from the opposing team is approaching you from the front with extreme speed and within milliseconds you have to decide which direction you are going to turn in order to avoid the tackle. At the last moment you suddenly shift to the opposite side. Your foot is still on the ground while your body is already moving sideways with speed. You hear a pop and immediately feel pain in the knee. This is an example of a non-contact injury.

Non-contact injuries account for about 70% of all ACL sprains. Twisting your knee, pivoting with your foot planted or landing awkwardly from a jump are the prime mechanism of injuries. Hyperextension of the knee (bending the knee the wrong way by more than 10 degrees causing it to gap at the back) or sudden deceleration i.e. coming to an abrupt stop whilst the foot is firmly planted, are also possible mechanisms of an ACL sprain.

Contact Injuries account for about 30% of ACL injuries. Usually a blow to the side of the knee when the foot is firmly planted on the ground e.g. with studs or spikes which forces the shin bone too far inwards or backwards.

Women are more likely to sustain knee ligament injuries
Women are three times more likely to suffer an ACL injury or knee sprain. This is thought to be due to a combination of factors including hormone levels, ligament structure, pelvis angle, hamstring flexibility and size of the ligament itself.

A ligament sprain happens when the ligament is overstretched.  There are several classifications for ligament sprains depending on the severity (grade 1, 2 or 3). The fibrous band is like a pulley, which prevents the joint from moving into extreme ranges. When the force is too big for the ligament to resist, the fibers will tear. Overstretching the ACL may result in tears or a sprain of the ligament.  It is important to know and understand the difference and implications. In the case of a tear, you may hear a snap or tearing sound.

The collagen fibers tear like a tension cable when overloaded and the fibers unravel. On a cellular level, injury will cause a split along the sheath of the ligament (like a sleeve around the ligament). Inflammation develops in response to injury which causes swelling, pain and loss of function, this causes the knee to buckle forwards. The swelling contributes to loss of space around the ligament that restricts the normal movement of the ligament in its sheath. Mucoid degeneration and fibrinoid necrosis (a type of cell death) indicate ligament tears.

A small amount of fibers torn, you will have some discomfort and pain. The ligament only sustained a mild stretch injury. No swelling and minimal pain, but you may run into problems if the cycle repeats itself. Recurrence of micro tears in the ligament could lead to more severe tears. You will have no loss of function or range of movement of your knee, but may experience pain at some point during the movement. You will be able to continue playing.

Recovery time for a grade 1 ACL injury is anything between 2-4 weeks. However, the collagen fibers only align after 6 weeks (maximal ligament strength), so to limit the possibility of re-injury it is advisable not to return to sport too soon.

A partial ACL tear with some swelling and bruising. Pain level increases quite a bit from a grade I and moving your knee will cause pain. It may feel uncomfortable to bend or straighten your knee and it may feel unstable, as if the knee wants to “give way”.

In a grade 2 ACL injury between 20% to 80% of the fibers are torn. You will not be able to put weight on the leg, in other words; take a normal step. Even if you try to continue playing, you will have a considerable amount of pain and limping. The pain will not allow you to straighten your knee or lift your leg forward (knee to chest).

Recovery Time will be 6 to 8 weeks (With early treatment, we try to get you jogging at 6 weeks).  Expect return to activity to be no sooner than 6 weeks.

A complete ACL tear. Swelling and discoloration (bleeding under the skin) are visible. The knee feels as if it wants to give way completely. Putting your full weight on the leg is nearly impossible. Bleeding and swelling will definitely be present.

The main concern with a grade 3 tear is the ligament’s ability to stabilize the knee joint – if the ligament tears into two separate flaps, there is no way the ligament can ‘heal’ or reattach without surgery. A Sonar or Diagnostic Ultrasound will show the full extent of the damage. Surgery is the best option to reconnect the separated segments of the torn Anterior Cruciate Ligament.

Often there will be no pain, but the disfigurement is quite obvious, since all the fibers are torn. It is important to know that there could be other structures involved with such an injury, but we will discuss this in more detail with our differential diagnosis later.

Recovery Time will depend on whether the conservative or surgery option is chosen. Conservative treatment may involve more than 8 weeks of intensive rehabilitation.  Surgery is indicated if a complete rupture of the medial collateral ligament is present with ACL injury and full recovery may take 4-6 months and return to sport only from 9 months.

Physical Examination

After taking a thorough look at your history, physiotherapists can determine which parts of your knee may be injured by finding the root cause of the problem.  We do specific tests for each structure in the knee, so we can differentiate between what is injured and what isn’t. If you’re uncertain, let us have a look and give you our opinion.

To test the integrity of the ACL we use the Lachman- , Anterior Drawer- and Pivot Shift tests. Using these tests we can accurately determine if there is an instability or torn ACL in your knee. In our assessment we also test the ligaments on the inside, outside and the menisci (cartilage) in the knee.

X-rays

X-rays can be helpful to exclude fractures of the patella, femur, tibia or fibula, but will not show an ACL ligament tear. This is usually the test most emergency rooms opt for, but when there are no fractures diagnosed, they conclude that the ‘knee ligaments’ are torn.  However, this doesn’t tell us much. Get to your physiotherapist so that they can test each ligament individually and get a more conclusive diagnosis.

It is important to note that children have softer bones. The anchor of the ligament can tear away from the bone more easily resulting in an avulsion fracture, which may be visible on x-ray. It is essential to make sure there are no fractures if we suspect an ACL injury in a child before proceeding with further tests.

MRI

The gold standard (best in the industry) to diagnose an ACL tear would be via MRI, then a CT scan. MRI has the advantage of providing a clear image of all the anatomical structures of the knee. An MRI can diagnose ACL injuries with an accuracy of 95% and will also reveal any related meniscal tears, chondral injuries, or bone bruises. However, this is an expensive test and you will need to consult an orthopedic surgeon to be referred for an MRI.

Ultrasound

If you have limited funds and would like to confirm your diagnosis, then we advise you to have a sonar or diagnostic ultrasound done at a reputable musculoskeletal sonographer. In this case, the ACL itself won’t be visible on the scan, but injuries to the structures around the ACL may lead us to assume an injury to the ACL. If this is the case, we may refer you for further testing to confirm, such as MRI or CT scans.

Physiotherapy treatment of an injured or torn ACL will start with a detailed assessment. This enables us to plan the course and goals of treatment. For example, the treatment plan and goals of a rugby player may differ from a long distance runner.

Physio modalities used to treat knee ligament injuries may include joint mobilisation if stiffness of the knee is present, electrotherapy and strapping for swelling and pain relief, myofascial release for muscle spasm and specific rehabilitation exercises according to the degree of the injury. Exercises will also be progressed as the injury heals with the end goal of returning patients to their previous level of activity. Education is also a major part of physiotherapy and you are encouraged to ask questions and provide feedback during the course of treatment.

1st Phase: Protection & initial Healing

P

Protect.

A knee ranger brace may be necessary to protect the ACL and limit movement of the knee joint.  If you experience pain when putting your full weight on the knee, you should use crutches when walking until you can tolerate full weight-bearing.

R 

Rest.

Do not continue training/sporting activity at this stage.  A physiotherapist will be able to guide you in gentle, pain free exercises to start strengthening muscles around the knee without putting excessive strain on the injured ACL.

It is also important not to return to sports (even if the pain improves) without having the knee assessed.  No pain does not necessarily mean the injury has healed completely.

I

Ice.

An ice pack or ice cubes wrapped in a towel over the injured knee may reduce pain and inflammation.  Ice can be applied for about  20 minutes every 2 hours, but always have a towel between the skin and the ice to prevent an ice burn.

C

Compress.

Strapping or an elastic compression bandage can be used around the knee joint to help control swelling which may also help with pain relief.

E

Elevate.

Lying on your back with your foot on a chair (your knee must be higher than your heart).  Raise your leg for 15 minute intervals during the day.

2nd Phase: Regain Full Extension of the knee

One of the most important components of ACL rehabilitation is to regain full range of movement of the knee joint. We use massage, stretches, neurodynamic- and joint mobilizations to achieve full range of movement.

In this phase of rehabilitation physiotherapy will focus on knee extension (straightening) as the knee ranger limits flexion (bending) of the knee to protect the ACL.  We will guide you with static exercises, for example pressing the knee down into a rolled up towel, to start regaining muscle control around the knee.  It is important to decrease swelling if the knee is still swollen at this point.

Once you can tolerate full weight-bearing you will progress to the next phase of rehabilitation.

Getting back to sport too soon: Not completing the rehabilitation process can be detrimental to your ACL. If you load it too much, too soon, the ligament will not be able to withstand the forces being put on it and you could sustain a re-rupture, starting the whole process right from the beginning, only this time with even more scar tissue to begin with. This can become a recurrent problem and may weaken the ligament to such extent that your knee becomes completely unstable.

Generic braces provide a false sense of security and sometimes athletes will return to sport still using a brace. If the muscles around the knee joint are not strong the brace will not prevent re-injury of the knee.

Waiting too long to come for physiotherapy due to the false sense of support the swelling provides. Swelling makes it more difficult to assess and diagnose the knee completely. (See excerpt on swelling in the knee at general knee ligament injuries)

Not attending to your injury apart from physiotherapy: Your physiotherapist will give you a home program you need to follow. We only see you for an hour maybe twice a week. The rest of the time, it is your responsibility to do what is necessary in order for complete healing to occur.

Grade 1 or 2 ACL injuries do not usually need surgery.  Conservative management (bracing and physiotherapy) is generally the best option for these kinds of injuries.  However, surgery may be indicated if the rotational instability (instability with twisting movements) doesn’t improve.  If the medial collateral ligament and medial meniscus were also injured (also known as an “unhappy triad of the knee”) you may also need surgery to repair the other injured structures.

In a grade 3 ligament tear (complete rupture of the ligament) the torn sections cannot re-attach by itself. Surgery is your best option and arthroscopy is the way to go as it is a minimally invasive technique. An ACL can’t be sutured back together, so the surgeon uses a technique called tissue graft.

They may harvest the hamstrings, patella tendon or the adductors to create an artificial tendon attached to the femur, which is like a scaffolding for the ligament to grow on.

This allows the body’s natural form of healing to take place. In the case of a complete ACL rupture, there are usually other structures involved, like the medial meniscus, thus an arthroscopic procedure allows the surgeon to investigate and repair these structures at the same time.

• Knee or patellar dislocations – weakness and laxity of your knee joint.
• Meniscal injuries – catching during twisting of your knee.
• Collateral ligaments injury – pain mostly inside or outside of the knee rather than the front (inside or outside ligaments).
• Medial Collateral Ligament tear (MCL injury) – pain on the inner knee.
• Knee tendinitis – Patellar tendon pain in the front of your knee.
• Posterolateral corner of the knee – area of pain more at the back of the knee.
• Patellar dislocation or fracture – unable to walk and pain with full weight bearing.
• Femoral, tibial or fibular fractures – deep pain that throbs even when not walking.
• Bursitis – pain just above or below the kneecap, an irritated and swollen fluid filled sack.
• Fat pad impingement – pinching of adipose tissue.
• Other types of knee injuries.