ACL Injury Guide – Causes, Diagnosis, and Treatment

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The Anterior Cruciate Ligament aka ACL is the major ligament that runs diagonally right in through the center of the knee. In addition to providing rotational stability to your knee, it plays a vital role in preventing the tibia (shinbone) from slipping out in front of the femur (thighbone). The ligament is a strong band of tissues that connect different bones. In case of ACL, it connects your femur to the tibia. A tearing of this ligament is known as ACL injury.

ACL injury usually occurs during intense sports, such as soccer, football, volleyball, basketball, skiing, and gymnastics, that involve frequent leg movements like jumping, sudden stops, or changes in direction. When the injury occurs, a popping sound can be heard in the knee. The knee may instantly start to swell or feel unstable, and it becomes painful to bear weight.

The treatment can range from rest and rehab exercises to surgery and replacement of the torn ligament followed by rehab, depending on the severity level of the injury. Proper warm up and a training program can be handy to minimize the risk of an ACL injury in future.

AAOS recommendation

Here are some of the recommendations by The American Academy of Orthopedic Surgeons for people who have a torn ACL or had it in the past

  1. To protect your knee joint, get reconstructive surgery within five months of the injury
  2. Get a musculoskeletal exam of your lower extremities
  3.   To diagnose any associated cartilage or joint issues, magnetic resonance imaging should be performed

What can cause ACL Injury?

As mentioned earlier, most injuries occur during intense physical activity or sports that put sudden stress on the knee. Several situations that can result in a torn ACL include sudden slowdown, changing direction, pivoting while your foot is planted firmly on the ground, incorrect landing from a jump, or receiving a blow to the knee. The tear can be partial or complete, and even a mild tear can overextend the ligament, however, it leaves it intact.

What are the symptoms of a torn ACL?

A loud popping sound or sensation in the knee, accompanied by severe pain, immobility, and loss of range motion are the instant symptoms that occur right after the injury. Moreover, the knee can gradually swell and result in a feeling of instability.

torn acl

What are the major risk factors?

Overweight people are at a greater risk of ACL injury. Moreover, women are also more susceptible as compared to men who play the same sports. There are two reasons behind this: firstly, women have a strength imbalance in their legs as their thighs are stronger than the hamstrings. Remember, hamstrings play the key role in preventing the shinbone from overextending the ACL. Secondly, studies have shown that women land from a jump in a way different from men, which results in a greater stress on the knee.

How to minimize the risk?

Researchers have shown that proper warm up before any intense physical activity, and regular exercises to strengthen lower torso, hips, and of course, legs can reduce the risks of an ACL injury.

When to seek medical help?

Rest, ice, compression, and elevation is a good starting point to relieve pain but here are the signs that tell you to see a doctor immediately:

  1. Severe pain and swelling
  2. Popping sound or sensation in the knee
  3. Painful to put weight on the affected leg
  4. Giving way, limping also raise red flags about a ligament damage

What type of specialist do you need to see?

You should see your primary care for initial assessment, although an orthopedic surgeon is a specialist who will eventually diagnose and treat your damaged ligament. If the injury occurred during a sporting event or training, a certified athletic trainer might first examine the player on the field. In case there’s a need for surgery, a physical therapist will be involved in ongoing treatment, before and after the surgery. A therapist might be involved for rehab even if the treatment doesn’t require surgery.

How is an ACL injury diagnosed?

The physician will ask you to go through a quick history of how the injury occurred and also any prior knee injuries. The diagnosis then begins with the physical examination of the knee, which can be hard with the swelling and pain. Anterior drawer test, pivot shift test, and the Lachman’s test are some of the maneuvers that the doctor can use to determine the nature of the injury. Plain X-rays can be done to detect any bone fracture that might have occurred along with an ACL tear, while MRI can evaluate the anatomy of the knee and detect any tears in ligaments or damage to the bone or meniscus.

What are the treatment options?

Treatment options include surgery or rehab through physical therapy. The type of treatment depends on your activity level. The International Knee Documentation Committee has defined four activity levels:

1. Includes extreme sporting activities such as jumping, hard cutting, and pivoting such as soccer, football, tennis, etc.

2. Side-to-side sports or continuous intense manual work

3. Light manual work, light sports such as cycling, running, etc.

4. Sedentary activity, no sports

People in level three and four are usually treated by rehabilitation and physical therapy, and surgery is hardly ever done. However, athletes who want to return to their original level of intense activity quickly will need surgery. In case of severe damage, the ligament might be replaced through the surgical process. Even if surgery is necessary, it’s not done immediately after the injury. There is a wait of about three to four weeks so that bleeding and swelling decrease and surgery can be planned.


A physical therapist plays a critical role in treatment and is involved in planning and pre-hab before surgery and rehab after surgery. Wearing an ACL tear knee brace can be a godsend during the rehab process to protect the ACL from any extra stress. The knee brace can be worn during sporting activities even after healing to minimize the risk of any future injuries. Recovery is usually measured in the number of months, and rehab can take up to nine months.

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