Health, Knee pain

ACL tear – Do you really need surgery?

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ACL tear non contact
When can I play again? Do I need surgery? These are the questions emotionally asked after anterior cruciate ligament injury. In this post i am going to answer these questions and more!

Torn your ACL and now wondering, do you really need surgery? The simple answer is: No – Only if you are a high level athlete, wish to return to pivoting/high demand sports OR have an unstable knee.

In this first post we will explore the difference in outcomes between surgery and conservative treatment and what that means for you: 

How do you know if you have an ACL tear?

If you heard a pop, snap or tear, the injury should be suspected as a ACL tear until proven otherwise. You may have felt something pop out or move  in the knee, this is sometimes confused for patella/knee cap dislocation but is most often an ACL tear.

You may or may not also feel clicking and locking which would indicate meniscal damage. Meniscal injury occurs in at least 40% of all meniscal tears(1).

Swelling will occur within an hour of injury, if swelling occurs a few hours later it points more towards meniscal tear.

But it is always best to get it thoroughly assessed by your local Sports Physiotherapist – It is not worth relying on Doctor Google or hoping it will go away!

Brief anatomy:

acl anatomuThe knee is formed by three bones, making up two joints. One joint is where the patella (knee cap) glides on the femur as you bend your knee. The other is formed by the tibia and the femur – This is the main joint that the ACL is in the middle of.

There are four main ligament that connect the femur and the tibia together and form this large hinge-like joint. These are the medial collateral(MCL), lateral collateral(LCL), anterior cruciate(ACL) and posterior cruciate(PCL) ligaments.

The ACL is right in the middle of the knee and prevents the tibia sliding forward on the femur and prevents excessive rotation.

Between the smooth articular surfaces of the tibia and femur and the menisci – the lateral and medial meniscus act as the shock absorber of the knee to prevent body injury, absorb shock and offer a smooth, rounded surface to move on.

Causes of ACL tear:

ACL injuries occur when the bones of the leg twist in opposite directions under full body weight, either during contact, or non-contact:

Non-contact ACL injury makes up about 70% of all ACL injuries, The two main mechanisms of non-contact injury are:

  • acl mechanismHigh impact jump-landing with a under-flexed (too straight) knee or valgus position (knee going laterally)







  • acl non contact 2Forceful rotation of the knee with the foot planted on the ground. This often happens when turning, side-stepping, pivoting etc.






acl tear contact

Contact ACL injuries:

The other 30% of ACL tears are due to contact and so are more random and due to a less preventable mechanism – There are often just plain unlucky.





Risk factors for ACL injury:

  • Poor sports specific conditioning
  • Muscle imbalance – The main one here is a low hamstrings-to-quadriceps strength ratio
  • Poor technique and awkward body movement
  • Poor neuromuscular coordination and balance

Risk factors that are hard to change:

  • Female gender
  • Joint laxity
  • Reduced ACL size and strength
  • Increased female sex hormones



In the USA alone, about 250 000 ACL injuries occur annually. This translates into a 1 in 3000 chance that a member of the general population will injure their ACL.(2)

And over half of these injuries are full ruptures of the ACL!

So that means an estimated 175 000 ACL reconstructions costing over US$2 billion each year.(3) That is a huge cost – especially if extrapolated world-wide! Unfortunately I can’t get a number on this but I’m sure you can appreciate that it is absolutely gargantuan.

This represents a huge financial cost for the health system AND for you with nearly half of ACL injuries undergoing surgery!

So imagine if it was found that there was no significant difference in outcome between surgery and conservative rehab?

Conservative rehab Vs Surgery – What are the outcomes? 

Re-Injury rate after reconstruction:

One of the big concerns following surgery is re-injuring the ACL or surrounding structures (e.g. meniscus or cartilage) upon returning to sport. This is because the re-injury rate IS HIGH – studies looking into this have found it can vary from 2.3% to 13%.(4) The reason for the reasonably large range here is because it does depend on the sport or activity that the player returns to.

The re-injury rate is in the higher spectrum if playing a pivoting sport. The re-injury rate is 12% when playing a pivoting sport such as rugby and football/soccer – This is an unacceptably high rate giving an almost 1 in 8 chance of re-injury!

Risk of Osteoarthritis:

Often patients are recommended surgery so that the risk of osteoarthritis (OA) is reduced, but this is simply not true.

The rate of return to sport, treatment method or how much loading the knee takes in the years after injury are not the main factors contributing to OA – The initial injury itself is the important factor contributing to OA. This is due to bleeding within and inflammation of the joint after injury that, although your symptoms resolve gradually (pain, limited range etc) and tears can be repaired surgically, trigger a remodeling process. This chronic remodeling triggered in the cartilage and other tissues in the joint leads to OA in the majority of cases.(7)

This results in roughly half of all ACL inured knees showing OA after 10 years and nearly 100% after 15-20 years.

Some studies have actually found that following re-construction there is more OA. Kessler et al 2008 found that although there was better knee stability after a re-con, there was significantly more OA when compared to conservative treatment (42% vs 25%).(6)

It is also worth mentioning that sports participation itself – without prior injury moderately increases the risk of hip or knee OA.

Conclusion: There is NO evidence to suggest that ACL repair prevents future arthritis.

So when is surgery called for?

People who SHOULD under-go reconstruction are those that:

  • Have on-going symptomatic instability, eg knee giving out
  • Are elite athletes


  • Wish to return to high-risk sports (pivoting sports)

The main reason for ACL reconstruction is to give an athlete a stable knee – So do not rush off to the surgeon if you do not have an unstable knee!

Follow this link for great information on:


Please Like, Share and Comment to let me know how you go and check out the below link to check your hip stability! Your hip controls the knee so this is very important!