In the United States, the typical patient who ruptures his or her anterior cruciate ligament (ACL) undergoes surgical reconstruction within a few weeks. However, there is more than a decade of data to suggest that this is not always the optimal or necessary course of care. A lot of this research has come out of our department at the University of Delaware, although there have been several national and international articles in the past few years that support the notion that ACL reconstruction may not be needed for all individuals after injury.

Why surgery?

Surgery is performed to restore passive stability of the knee joint (passive being the key word here). Restoration of this stability serves two purposes:

1) Allow patients to return to high-level sports that involve cutting, twisting and pivoting (Read: Preventing short-term disability).

2) Reduce the risk of osteoarthritis by restoring normal arthrokinematics and preventing shear and compressive forces that load the articular cartilage in regions that should not be maximally loaded (Read: Preventing long-term disability).

So, now that we have decades of research on ACL reconstruction, does surgery serve to address these two functions? Yes and No.

How do we decide who will benefit from ACL reconstruction?

Two groups have emerged over the past several years – the Copers and the Non-Copers (See this article about Copers and Non-Copers). Essentially, Copers are individuals who do not have episodes of instability, have knee function and biomechanics similar to their non-operated knee and are able to use coordinate muscle strategies to overcome a lack of passive instability. Non-copers have a knee that is unstable, has abnormal biomechanics cannot use coordinated muscle strategies to develop dynamic stability that is sufficient to allow them to participate in higher level athletic activities. The general thought was that Copers would not require ACL reconstruction and Non-Copers would require surgery to resume normal participation.

What is interesting is that before surgery, Copers and Non-Copers look similar. Afterwards, there is no difference in laxity of the joint as measured by a KT1000 arthrometer (that is to say they both have similar amount of anterior tibial translation when tested in a passive manner). However, the Non-Copers complain of instability and poor knee function despite rehabilitation and Copers are able to return to higher levels of function without surgery.

The big question is: How do we determine who is potentially a Coper and would benefit from the non-operated treatment and rehabilitation. Several methods of identifying these subjects have been developed. At the University of Delaware we use the following criteria to identify who is a Potential Coper and may benefit from rehabilitation instead of surgery.

Potential Copers (Candidates for non-operative management)

  • Timed hop test score of 80% or more of the uninjured limb
  • Activities of Daily Living Scale score of 80% or more
  • Global rating of 60% or more during a 6-month post-injury follow-up period
  • No more than one episode of giving away

 Are Potential Copers really the ones who end up “Coping”?

Although we like to think that we can predict who will be Copers and who really are the “Motor Morons,” it turns out that people can change over time. In a prospective 1-year study of patients who did and did not undergo surgical reconstruction (see article here), it turns out that not all Potential Copers turn into True Copers, and not all Non-Copers stay Non-Copers one year after injury. This article was published in Moksnes, Snyder-Mackler and Risberg in JOSPT in 2009.

60% of those identified as Potential Copers turned out to be True Copers at 1 Year, 40% turned out to be Non-Copers at 1 Year.

30% of those identified as Non-Copers at Baseline turned out to be True Non-Copers at 1 Year, 70% of those identified as Non-Copers at baseline turned out to be True Copers at 1 Year follow-up.

The flow-chart below is taken from PubMed Central (

flow chart

What does this all mean? It means for the most part we are decent at picking out who the True Copers might be, but we are not so good at deciding who the True Non-Copers might be. Maybe some of those we recommend for surgery should try rehabilitation before undergoing ACL reconstruction because they may just become Copers over time. This begs the question: Does waiting to undergo surgery have a negative effect on outcomes. This was the question of a recent RCT by Frobell et al. published in British Medical Journal and turns out the answer is No. Waiting to undergo ACL reconstruction will NOT negatively affect long-term outcomes.

To wait or not to wait; To operate or not to operate?

There is much concern that waiting to undergo ACL reconstruction will negatively affect long-term outcomes. There is also concern that avoiding surgery all together will result in earlier onset of osteoarthritis. Turns out that both of these thoughts are not supported by two recent well-designed studies.

Frobell et al. recently published the 5 year results from their randomized controlled trial in which patients with ACL rupture were assigned to one of two groups: 1) Rehabilitation plus ACL reconstruction within 10 weeks of injury or 2) Rehabilitation with option for surgery 6 months or more later. Only about 50% of those in the second group ended up receiving ACL reconstruction. These results were very telling. There was no difference in osteoarthritis progression, need for meniscal surgery, or self-reported functional ability between patients who underwent early surgery, delayed surgery or did not undergo surgery at all.

In 2009, Meuffels et al. published their report of a matched-based analysis of high level athletes who did and did not undergo ACL reconstruction after ACL rupture. Their results showed no difference in osteoarthritis incidence, meniscal lesions, activity level, self-reported function and objective functional performance between subjects who did and did not undergo reconstruction. However, those who did undergo surgery had better joint stability, even though it seemed not to improve their functional performance.

How to treat patients electing Non-Operative Management?

So if your patient does not want to undergo surgery, what type of rehabilitation protocol should you employ? It appears that the ability to overcome the lack of passive stability provided by the ACL requires coordinated muscle activity. This dynamic stability should form the core of the rehabilitation protocol (not that addressing weakness, pain, inflammation, range of motion, etc. should be ignored). I won’t give all of the details, but a progressive perturbation training program has been developed at the University of Delaware that has been shown to reduce co-contraction, improve outcomes and improve dynamic joint stability. This program has been described in the Physical Therapy Journal (found here) and in the Journal of Orthopaedic and Sports Physical Therapy (found here).

Regardless of course of care, exceptionally high incidence of OA after injury.

Despite the course of care, the future incidence of developing osteoarthritis is exceptionally high. Incidence has been reported to range from 10% to more than 85% in patients who experienced an ACL injury. Some studies have compared the operated to the non-operated limbs and found a 6-fold increase in risk for developing knee OA in the knee that experienced an ACL rupture. Despite this exceptionally high incidence, we still truly do not know why this occurs. Biomechanical factors have been suggested to be a primary player in developing future disease. Andriacchi et al. have developed a computer-based model of how OA progression may occur and their results seem to align with clinical observation of cartilage degeneration (see article here). I am certain that this area of research will be exploding in the next several years as more and more older adults with a previous ACL injury develop signs and symptoms associated with OA. If we can identify which factors specifically lead to OA progression in this population so we can develop preventative strategies to reduce future disability.

— Written by Joseph Zeni

EDIT 2/3/13

There is one important consideration if you plan to do any pre-operative screening. Because the higher level hops may be more demanding than any other activities your patient has done since the rupture, preventing further injury is a concern. In our clinic all non-operative patients are braced when doing the hop testing. This limits the chance a patient will experience a buckling event during the testing and damage other articular structures.