Anterior Cruciate Ligament Reconstruction (ACLR) is one of the most common surgeries performed due to a sports injury. ACLR rehab and ACL prevention training is one of the hottest topics in the sports medicine world. The reality is while 80% of ACL reconstruction (ACLR) patients return to some form of sport, only 65% return to the same sporting level and 55% return to sport at a competitive level within 1-2 years post ACLR (reference).
The Return To Sport Journey
Unfortunately for those who are not professional athletes, the return to sport (RTS) path after ACLR is very unpredictable. There are so many ebbs and flows, and twists and turns, that it is almost impossible to predict. The main reasons for this is that the rehab program is bloody hard work and life gets in the road.
For the professional athlete however, the RTS path is a little bit more predictable, and you’ll find that a high percentage of them will be back training and playing sport within 8-12 months. There are many reasons for this, with the main reasons being they get paid to do their rehab, they have a large team of medical services at their disposal, there are external pressures from a number of different stakeholders to RTS as soon as possible, and they are more likely to be much fitter and stronger than most of the age-matched general population.
RTS Performance Testing Research
What is becoming clear however, in regards to predicting a safe and successful RTS, is that recent research is indicating that the decision to RTS should be based on meeting key performance criteria, rather than allowing the player to RTS based on time-frames alone, or getting cleared to play from the orthopedic surgeon based on a series of static clinical tests.
The results of two recent studies looking at ACL re-injury rates have been summarized below…
Grindem et al (2016)
- They looked at 106 competitive athletes who recently had ACLR surgery and they had 5 key performance criteria they wanted the player to achieve before clearing the player to RTS. They were;
- Quads strength within 10% of the uninjured side
- 4 single leg hop tests; with no more than 10% difference between sides
- 38% of athletes who RTS despite not passing RTS criteria re-injured their ACL
- Only 5% of athletes who did meet all 5 RTS criteria re-injured their ACL
- Of the players who re-injured their ACL, 39% of them did so when they RTS earlier than 9 months, whereas 19% reinjured their ACL when they waited to RTS after 9 months
- This lead the authors to conclude that for every 1 month delay in RTS, the re-injury rate was reduced by 51%
- Lastly, and is in fact no surprise, 4 of the subjects in this trial who RTS within 5 months of their ACLR (against medical advice), all subsequently re-injured their ACL within 2 months of playing sport.
Krytsis et al (2016)
- These authors looked at 158 athletes and used the same key RTS performance criteria as mentioned above, with the addition of an agility drill (T-Test)
- All of the 158 athletes in this group returned to previous competitive level of sport at an average of 229 days (approximately 8 months) post-op.
- 26 players (16.5%) re-injured their graft at some point with 17 (65%) of them re-injuring their ACL within 6 months after RTS.
- Furthermore, 11 (7%) injured their other ACL.
- In regards to meeting performance criteria prior to RTS, 33% chose to RTS despite not meeting all 6 key criteria and subsequently reinjured their ACL,
- Only 10% of the players who did met all 6 criteria, and were passed fit to RTS, subsequently reinjured their ACL.
How To Assess Performance Prior to RTS
Single Leg Hop Test
The goal of this test is to jump as far as possible on each leg, aiming to “stick” the landing. The performance goal is to have the recently injured limb within 10% of the uninjured limb. Poor performance on this hop test (>10% difference between limbs) can identify those at risk of re-injury.
Using technology from force plates, we can appreciate the ground reaction force (GRF) vector during the landing phase of the task. In the top left box of the first video, the vector is medial to the knee. If the vector were to move laterally outside the knee due to compensatory trunk lean or the knee collapsing in, there would be an increased valgus moment on the knee. The position of knee valgus places an increased load on the ACL. Uncontrolled, excessive dynamic knee valgus with a high acceleration rate is what ultimately can tear the ACL. What is dynamic knee valgus? Learn more
Triple Hop Test
The goal of this test is to consecutively hop three times as far as possible on the same leg, aiming to “stick” the final landing. The performance goal is to have the recently injured limb within 10% of the uninjured limb. Poor performance on this hop test (>10% difference between limbs) can identify those at risk of re-injury. This test is especially important to assess prior to RTS as it puts a very high demand and impact on one leg. It is a great movement test to look at strength, stability, and motor control.
Not only should you assess the final landing, but also the initiation and landing of each hop! You can appreciate more dynamic knee valgus during the second hop landing compared to the final hop landing.
Crossover Triple Hop Test
The goal of this test is to consecutively hop three times as far as possible on the same leg while alternatively crossing over a line, aiming to “stick” the final landing. The performance goal is to have the recently injured limb within 10% of the uninjured limb. Poor performance on this hop test (>10% difference between limbs) can identify those at risk of re-injury.
This test is unique from the others as it adds a lateral component to the movement. With this addition, there is an increase in frontal and transverse plane forces directed at the knee. In this video, jumping from right to left in the medial direction is more challenging as it increases the valgus moment placed on the knee as compared to jumping the other direction. This requires the athlete to work harder to decelerate the knee from moving through excessive dynamic knee valgus. You can appreciate the differences between the second and final landing!
Six Meter Timed Hop Test
The goal of this test is to consecutively hop as fast as possible on the same leg for six meters, aiming to “stick” the final landing. The performance goal is to have the recently injured limb within 10% of the uninjured limb. Poor performance on this hop test (>10% difference between limbs) can identify those at risk of re-injury.
This test is unique from the others as it adds a time component goal to the movement. With this addition, the athlete’s focus could shift from quality of the movement to the quantity (time) spent performing the test. It is important to remind the athlete not to sacrifice the quality of their movement for a better time.
One thing to take away from these trials is that you can still re-injure your ACL graft despite meeting the key RTS performance criteria, but your risk is much much lower if you do.
One thing to also note is that from the second trial I summarized, the average time for the players to RTS was only 8 months, whereas the first trial recommended that RTS be delayed to at least 9 months. It would very interesting to see if the re-injury rates of the second trial would be lower if the players were given an extra month, at least, to continue with further strength and conditioning and neuro-muscular retraining. If you believe hip weakness is potential factor limiting the player from returning to sport, be sure to check out this article for hip stability ideas.
In summary, we should be educating our patients and athletes that they can return to training and RTS with a reduced risk of ACL re-injury, anytime after the 9 month mark. However, before they even contemplate stepping on to the field for a competitive game, they should also be cleared clinically by their orthopedic surgeon and they absolutely must meet ALL the following key RTS criteria before doing so:
- Quads strength: no more than 10% difference between sides
- 4 single leg hop tests: no more than 10% difference between limbs
- T-Test agility drill performed in under 11 seconds.
- Note: The last study also mentioned that an abnormal hamstring to quad ratio was found during testing that was a contributing factor to future ACL injury. This testing was performed on a laboratory machine (isokinetic) which is difficult to translate clinically. For those who have access to hand-held dynamometry; As a general rule the player should also have a Quad:Hamstring ratio of <1.5:1 before RTS
One very important thing to remember is that these key performance criteria should also be tested in a fatigued state at the end of a training session, as it is well established that fatigue has been shown to be a contributing factor to ACL injury. Remember, we need to be training and testing our players for the worst-case scenario of their sport, not just the average demands! If your athlete’s sport is soccer, be sure to incorporate these soccer prehab exercises in their training program!
As always please feel free to share this post with colleagues, patients, family and friends, and please comment if you have other RTS tests that you like to do with your patients/athletes. As I have said many times before, I have a passion for injury prevention, so the more this research can be spread far and wide, the more health professionals will be on board with this information, then the better outcomes we’ll see in all of our patients long into the future! So there you have it, a pretty solid evidence-based approach to determining an athlete’s or patient’s readiness to RTS after ACLR.
A big thank you to MovementF1rst located in Newport Beach, CA for hosting us to film the videos for this article!
Grindem H, Snyder-Mackler L, Moksnes H, et al. Simple decision rules can reduce reinjury risk by 84 % after ACL reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med. 2016;50(13):804–8.
Kyritsis P, Bahr R, Landreau P, Miladi R, Witvrouw E (2016) Likelihood of ACL graft rupture: not meeting six clinical discharge criteria before return to sport is associated with a four times greater risk of rupture. Br J Sports Med 50(15):946–951
About The Author
Mick Hughes is the Head Physiotherapist and High Performance Manager for the Collingwood Magpies Netball Team in the Suncorp Super Netball League. He also consults part-time at The Melbourne Sports Medicine Centre. Clinically his area of interest is the lower limb, specifically the knee and ankle.