ACL Injuries and Tears

What is an ACL Tear?

By: Ehren Allen, PT/Certified Manual Therapist

The anterior cruciate ligament is one of the main stabilizing ligaments of the knee. The ACL is a thick band of tissue that connects the femur (thigh bone) with the tibia (weight-bearing leg bone) and its main function is to prevent anterior translation (or forward movement) of the lower leg during functional movements. 

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Types of ACL Tears?

There are three main categories of ACL injuries: Grade I, Grade II, and Grade III.  

  • Grade I:  Slight stretch of ligament fibers 
  • Grade II:  Partial tearing of ligament fibers 
  • Grade III:  Complete tear or rupture of ligament fibers

Is an ACL Rupture the Same as a Tear?

 A tear of a ligament is when some of the fibers of the ligament are are disrupted.  A rupture of a ligament is when all of the fibers of the ligament are torn or it is classified as a complete grade III tear.  

Does a Grade II ACL Tear Require Surgery?

Choosing whether or not to get surgery due to a Grade II ACL Tear is typically decided between the physician and the patient. If a physician notices a lot of instability in the knee, then surgery will most likely be suggested. Usually ACL injuries where more than 50% of the ligaments in the knee are torn are surgically repaired. This also is dependent upon the patient's activity level, their age, and fitness level. 

What are the Causes of ACL Tears?

ACL injuries commonly occur during athletic participation due to in the increased force that occurs during sports-specific movement patterns.  

ComACL tears by JOIImage of ACL Tears and Injuries
mon mechanisms that result in ACL tears include: 

  • Forced hyperextension (forceful straightening of knee with planted foot)
  • Sudden twisting movements with planted foot
  • Abrupt stops during physical activity/athletic participation
  • Jumping 
  • Multi-directional pivoting activities 
  • Forceful contact at knee joint (collision) 

Other Risk Factors?

ACL injuries tend to occur frequently in the female athletic population due to differences in body structure. Female athletes frequently exhibit muscular imbalances in the lower body known as quad dominance.  

For those with this condition, there is an unequal quad to hamstring ratio that results in weaker posterior leg musculature. Such weakness in the hamstrings can put the female athlete at increased risk of an ACL injury, as the hamstrings are unable to fire efficiently to reduce hyperextension and strain on the ACL. 

In addition, female athletes are at greater risk for structural genu valgum (or knock-knees) positioning that can result in increased knee stress when landing during jumping activities. Preventative lower extremity screenings, core stabilization strengthening, and review of proper jumping/landing techniques can all help to reduce the risk of ACL injuries in the female athlete. 

How Do I Know if I Tore My ACL?

Image of the Knee Joint
Common symptoms of acute ACL injuries include:

  • Audible “pop” at time of injury.
  • Severe pain in the front of the knee. 
  • Decreased range of motion  (inability to bend or straighten knee)
  • Significant swelling in knee joint (due to bleeding from injured ligament)
  • Bruising 
  • Inability to weight-bear due to pain/feeling of instability or “giving-way”.

Acute vs. Chronic ACL Tears?

Immediate care for ACL tears include the use of anti-inflammatory medications and RICE:

  • Rest: Reduce knee joint inflammation (including use of crutches for non-weightbearing)
  • Ice:  Used to reduce inflammation/pain (20 min intervals)
  • Compression: Compression bandage used to reduce joint swelling. 
  • Elevation:  Elevate limb (preferably above heart level) to reduce joint swelling. 

ACL tears are typically treated via 2 methods: rehabilitation and surgical repair.  While all patients with ACL tears can benefit from general range of motion and lower extremity strengthening activities following injury, some severe tears require surgical intervention to restore the integrity of the knee joint.

Benefits of surgical repair with post-surgical rehab include: restoring the functional stabilization of the knee to decrease the chance of further injury and resume daily tasks. 

Individuals who decline surgical intervention are prone to chronic knee instability, buckling, and giving-way. Those who are ACL deficient are often unable to sufficiently stabilize the knee during functional movements, potentially causing damage to the articular cartilage or meniscus. Over time, this type of residual damage to the joint structures may lead to osteoarthritis.  

Can a Complete ACL Tear Heal Itself?

Grade III ACL tears almost always require surgery in order for them to heal correctly. This is because there is a complete tear in the fibers of the knee ligament causing extreme knee instability. 

ACL Rehabilitation

ACL rehabilitation programs are developed with the following treatment goals in mind: Restoring functional knee stability, restoring full knee range of motion, and improving quad strengthening to support the demands of activities of daily living.  

Some of the most important rehabilitation activities to promote lower extremity flexibility and strength include:

  • Quad sets: Used to promote functional stability by activating the VMO musculature of the knee.This activity consists of performing isometric quad contractions (tightening quad while pushing the back of knee against a towel roll). May be used in combination with Russian strengthening (e-stim) for quad activation/muscle re-education. 
  • Straight Leg Raise: Used to promote functional quad strengthening.  This activity is very important is determining functional weight-bearing status and bracing restrictions. Typically, the patient must be able to perform an active SLR with good form (no extension lag) in order to progress the PT program.
  • Heel Slides: Used to promote the return of knee flexion. It is very important to restore full functional range of motion so that the patient can resume daily functional tasks such as walking, stair-climbing, and squatting. This activity is best performed using a towel under the patient’s heel with a rope secured around the foot, the patient then pulls the rope causing the knee to bend into a tolerable about of knee flexion. Ideally, ROM is restored to match the non-affected limb – with a minimum of 120 degrees of knee flexion to perform ADL’s. 
  • Ankle Pumps: Used to promote lower extremity circulation and reduce swelling. This activity is particularly important because it promotes blood flow to the lower extremity, reducing the risk of DVT (blood clots). This activity is best performed by pushing the foot down like gas pedal pumps or performing circular ankle movements.
  • Hamstring Stretch: Used to promote HS flexibility and restore knee extension. This activity may be combined with the use of a heel prop to promote functional extension, as the ability to fully straighten knee is important in restoring normal gait pattern. This activity is most effective with a hold duration of at least 30 seconds to promote soft tissue mobility.  


If you want to learn more about orthopedic conditions, give us a call at JOI - 2000 or go to JOIONLINE.NET.

If you want to learn more about Football Injuries, go to: https://www.joionline.net/library/show/football-injuries/


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