Joint Knowledge: The ACL

ACL injuries are among the most common types of knee injuries, usually occurring during activities that require sharp turns, high-impact jumping and landing, physical force to the knee, and sudden stops and starts. These include sports such as basketball, soccer, football, tennis, skiing, and mixed martial arts.

In today’s post, we’re going to take a closer look at this little ligament.

What is the ACL?

Located in the middle of the knee, the anterior cruciate ligament (ACL) is a band of tissue that connects and helps stabilize the femur to the tibia. It prevents the tibia (that is, the lower leg bone) from sliding forward and out of place.

Wondering where the term “cruciate” fits into things?  It relates to the cross-like formation it takes within the knee along with the PCL (posterior cruciate ligament).  Take a look at the images below.  The image on the left is a view of the front of the knee; the image to the right a view of the back.

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How to Spot an ACL Injury

Most ACL injuries with a loud pop or cracking sensation in the knee. Soon afterward, the knee will swell and cause significant discomfort when attempting to bear weight. Walking, crouching, and standing up from a seated position may become difficult. You may feel as though your knee will give way. Flexing and extending the surrounding muscles may also cause discomfort. The degree of these indications varies depending on the severity of the ACL injury.

Depending on the severity of your ACL injury, treatment may include rest and rehabilitation exercises to help you regain strength and stability or surgery to replace the torn ligament followed by rehabilitation. A proper training program may help reduce the risk of an ACL injury.


Check out these two exercises to strengthen your knees.


ACL Injury Causes

ACL injuries usually occur during high-intensity movements that recruit the knee joint. Sudden movements that involve rotation such as cutting, pivoting, and abrupt stopping are the most common causes. Significant force to the knee, such as a tackle or leg kick can also damage the tissue. Depending on the nature of the injury, the ACL tissue may be partially or entirely torn.


What to Do If You Have an ACL Injury

If you experience any of the signs of an ACL injury, seek medical care ASAP. Failure to seek care and/or continued activity can worsen the damage to the ACL. Even if the injury is mild enough that you can still bear weight on the knee, it is vital to get a professional diagnosis to avoid complications. Depending on the severity of the ACL injury, a medical professional may recommend RICE (rest, ice, compression, and elevation), physical therapy, or surgery.


ACL Injury Risk Factors

The following risk factors may increase your likelihood of incurring an ACL injury:

  • Performing high-impact movements such as those in basketball, soccer, football, tennis, skiing, mixed martial arts, and gymnastics.
  • Wearing footwear that fits improperly and/or lacks support.
  • Lack of exercise and particularly weak glutes and quads
  • Using poorly maintained equipment or protective gear
  • Running or jumping on unfamiliar or unnatural surfaces


Due to differences in skeletal structure and hormone activity, women have a higher risk of ACL injury than men.


Long-Term Effects of an ACL Injury

Severe or recurring ACL injuries increase the risk of arthritis of the knee. The risk is higher for people with additional injuries in the ligaments of the knee such as the medial collateral ligament (MCL), lateral collateral ligament (LCL), and posterior cruciate ligament (PCL). Whether the treatment is physical therapy or surgery, it is vital to allow time for proper recovery before attempting high-impact movements.


How to Prevent ACL Injuries

Prevention is key to avoiding any injury. Taking the proper precautions can help minimize the risk of an ACL injury:

  • Warm-up before and cool down and stretch after high-impact exercise.
  • Strengthen the muscles around the knee, including the quadriceps, hamstrings, calves, and anterior tibialis. Effective strength exercises include squats, hamstring curls, leg extensions, and calf raises.
  • Strengthen the hips (i.e., glutes) and abdominal muscles to provide greater overall stability.
  • Practice proper jumping and landing techniques.
  • Practice proper pivoting and cutting techniques.
  • Perform regular conditioning exercises such as running, cycling, jump rope, interval training, and other exercises catered to your sport.
  • Avoid running or jumping on uneven or slippery surfaces.
  • Wear comfortable, proper-fitting shoes and other gear applicable to your sport. Inspect all gear regularly and replace damaged ones that are damaged or fail to give the proper protection/support.
  • Get adequate rest and allow your body to recover between intense training sessions.


In most cases, proper strengthening and conditioning can minimize the risk of injuring the ACL. Gauge your fitness level relative to the activity, and avoid taking unnecessary risks. For more information on injury prevention, talk to a trainer, physical therapist, or specialist in your sport.


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