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Knee pain can stop you in your tracks, and a common cause of knee pain and instability is an ACL tear.  What is an ACL?  What causes an ACL to tear?  How to tell if you tore your ACL?  What are the signs and symptoms of an ACL tear? Can you still walk if you have a torn ACL?  What should I do if I think I tore my ACL?  Let’s dig in.

What is the ACL? 

The anterior cruciate ligament (ACL) is a key stabilizer of the knee.   The ligament extends from the thigh bone (femur) to the shin bone (tibia) and limits forward and rotational movement of the knee.  Tears in the ACL can occur as a result of trauma, and rapid pivoting and cutting movements.  ACL tears account for 64% of athletic knee injuries in pivoting sports resulting in 120,000- 200,000 ACL reconstructions annually in the United States (1).

Causes of ACL Tear

There are three principal causes of ACL tears.

Direct Contact

A person or object directly strikes the knee.  This is common in many sports especially football and soccer.

Indirect Contact

A person or object strikes a part of the body other than the knee itself causing excessive forces to be transferred to the knee.  Examples include basketball and martial arts.

Noncontact

Examples include hyperextension of the knee, incorrect landing, abrupt stop, and pivoting with the foot firmly planted.  Noncontact mechanisms account for 60-70% of ACL injuries (2).

What are the Signs and Symptoms of an ACL tear?

How to tell if you tore your ACL?  There are numerous signs and symptoms of an ACL tear.  Symptoms may vary from patient to patient.  The most common ones are:

  • A loud pop
  • Severe pain
  • Rapid swelling
  • Reduced range of motion
  • Knee  “gives away”  when bearing weight
  • Difficulty or inability to  walk or stand

Abnormal Physical Examination

Your doctor will assess your knee for swelling, range of motion and strength.  There are specific tests for the knee.  The two most common tests to determine if you tore your ACL include (3).

Lachman Test how to tell if you tore your ACL

The exam is performed with the knee slightly flexed.  One hand is placed on the thigh bone and the other on the shin bone.  The thigh bone is then pulled forward to assess the integrity of the ACL.

Anterior Drawer Test

The knee is flexed to 90 degrees and the shin one is pulled forward with both hands.  Excessive forward motion in relation to the thigh bone is suggestive of an ACL injury.

Can You Still Walk if You Have a Torn ACL?

There are three principal types of  ACL injuries.  A partial-thickness tear is where only a portion of the ligament is torn.  A full-thickness tear occurs when the tear extends across the entire ligament.  A complete tear with retraction occurs when the ligament fibers physically pull away from one another, similar to when a rubber band breaks.   Symptoms vary but most ACL tears cause pain, swelling and limited ability to walk or bear weight.

Can X-ray Show Torn ACL?

No!  X-rays can only visualize boney structures such as the thigh bone (femur) or shin (bone).  Ligaments, tendons, and muscles can not be seen on x-rays which is why if your question is how to tell if you tore your ACL, the answer is x-ray is not the appropriate test.  MRI is the best study to diagnose an ACL injury.

What Should I Do if I Think I Tore my ACL?

If you have severe knee pain, swelling, limited range of motion and heard a pop during an activity you most likely have torn your ACL.  Your next steps are important and should include

Immobilize

Elevate

Safe Anti-inflammatory Medications

Medical Consultation

Treatment options will vary depending upon the severity of the injury.   Most patients will be referred to an orthopedic doctor who in the majority of the cases is an orthopedic surgeon.  Orthopedic surgeons by training have an inherent bias toward surgery

What Is ACL Surgery?

A surgical procedure that involves cutting out the torn ACL and replacing it with either a cadaveric graft or the patient’s own patellar or hamstring tendon. The graft or ligament is then secured by anchors that are placed in the thigh and shin bones.   The procedure is performed in a hospital or ambulatory surgical suite lasting one to two hours. ACL surgery is major surgery and requires extensive rehabilitation.  There are multiple issues associated with surgery aside from the traditional risks of surgery which include bleeding, infection, and escalation in pain.

Failure:  Retear of ACL

  • At 5 years follow up after ACL reconstruction 12% of patients sustained second ACL injury (4)
  • At 15 years follow up after ACL surgery 29-34% of patients suffered a second ACL injury. (5)
  • Patients under 25 years of age are four times more likely to retear their ACL after reconstruction surgery than those over 25 years of age (6)

Knee Instability

A person’s native ACL has two bundles that are critical to the stability of the knee.  Surgical reconstruction removes the two native bundles which are then replaced with a single bundle graft.  This single graft can lead to knee instability which in turn can create excessive wear and tear on the cartilage, meniscus, tendons, and ligaments.

Diminished Performance

Muscle control and performance is compromised after surgery which accounts for many professional athletes inabilities to return to their pre-surgery performance (7)

Increased Risk for Knee Arthritis

A recent study that followed 164 patients at a mean of 14 years after ACL reconstruction demonstrated a 3 fold increase in osteoarthritis when compared to the opposite healthy knee (8).

Are There Nonsurgical Regenerative Options?

Absolutely!  The Centeno-Schultz Clinic pioneered the use of bone marrow-derived stem cells in the treatment of ACL tears. The procedure which is termed the Perc-ACLR (percutaneous ACL reconstruction) was developed in 2011. Two studies have been published to date in peer-reviewed journals (9) (10).  The 2018 study demonstrated that 77% of patients showed significant improvement in objective integrity in the ACL at 8 months (10). These patients also went back to full sports activity at a very high rate and low re-tear rates.  The injection is not easy and can not be performed by your family doctor or orthopedic surgeon.  Click below to see my Centeno-Schultz Clinic ACL injection.

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In Conclusion

The ACL is a key stabilizer in the knee.  It is susceptible to injury due to direct contact, indirect contact, and other causes.  How to tell if you tore your ACL?  The signs and symptoms of an ACL tear include a loud pop, severe pain, rapid swelling, instability,  and difficulty with walking or standing. MRI is the best study to diagnose an ACL injury.  Surgery is not the best option as it has multiple complications which include re-tears, knee instability, diminished performance and risk for arthritis.  A novel nonsurgical procedure called Perc-ACLR (percutaneous ACL reconstruction) uses a patient’s own bone marrow concentrate to repair ACL injuries.  Two peer-reviewed studies have demonstrated its success allowing patients to avoid the risks of surgery and viral contamination.  If your ACL surgery was canceled due to the COVID-19 pandemic now is a great time to reconsider your options.  Telemedicine consults are available from the comfort of your home.


1. Kim S, Bosque J, Meehan JP, Jamali A, Marder R. Increase in outpatient knee arthroscopy in the United States: a comparison of National Surveys of Ambulatory Surgery, 1996 and 2006. J Bone Joint Surg Am. 2011;93(11):994-1000.DOI: 10.2106/JBJS.I.01618.

2.Cimino F, Volk BS, Setter D. Anterior Cruciate Ligament Injury: Diagnosis, Management, and Prevention. Am Fam Physician. 2010;82(8):917-922

3.. Raines BT, Naclerio E, Sherman SL. Management of Anterior Cruciate Ligament Injury: What’s In and What’s Out. Indian J Orthop. 2017;51(5):563-75.

4.. Salmon L, Russell V, Musgrove T, Pinczewski L, Refshauge K. Incidence and risk factors for graft rupture and contralateral rupture after anterior cruciate ligament reconstruction. Arthroscopy. 2005;21(8):948-57.DOI: 10.1016/j.arthro.2005.04.110.

5.Leys T, Salmon L, Waller A, Linklater J, Pinczewski L. Clinical results and risk factors for reinjury 15 years after anterior cruciate ligament reconstruction: a prospective study of hamstring and patellar tendon grafts. Am J Sports Med. 2012;40(3):595-605.DOI: 10.1177/0363546511430375.

6. Kamien PM, Hydrick JM, Replogle WH, Go LT, Barrett GR. Age, graft size, and Tegner activity level as predictors of failure in anterior cruciate ligament reconstruction with hamstring autograft. Am J Sports Med. 2013;41(8):1808-12.DOI: 10.1177/0363546513493896.

7.Patterson MR, Delahunt E. A diagonal landing task to assess dynamic postural stability in ACL reconstructed females. Knee. 2013;20(6):532-6. DOI: 10.1016/j.knee.2013.07.008.

8. Barenius B, Ponzer S, Shalabi A, Bujak R, Norlén L, Eriksson K. Increased risk of osteoarthritis after anterior cruciate ligament reconstruction: a 14-year follow-up study of a randomized controlled trial. Am J Sports Med. 2014;42(5):1049-57. DOI: 10.1177/0363546514526139.

9. Centeno C, Markle J, Dodson E, et al. Symptomatic anterior cruciate ligament tears treated with percutaneous injection of autologous bone marrow concentrate and platelet products: a non-controlled registry study. J Transl Med. 2018;16(1):246. doi: 10.1186/s12967-018-1623-3.

10. Centeno CJ, Pitts J, Al-Sayegh H, Freeman MD. Anterior cruciate ligament tears treated with percutaneous injection of autologous bone marrow nucleated cells: a case series. J Pain Res. 2015;8:437-47. doi: 10.2147/JPR.S86244.