Sports Medicine Research: In the Lab & In the Field: Quadriceps Function in Braced ACL Reconstructed Patients (Sports Med Res)


Wednesday, September 12, 2012

Quadriceps Function in Braced ACL Reconstructed Patients

Quadriceps function after exercise in patients with anterior cruciate ligament-reconstructed knees wearing knee braces

Davis AG, Pietrosimone BG, Ingersoll CD, Pugh K, and Hart JM. J Athl Train. 2011 46 (6). 615-620. (Full text available for free online)

Following anterior cruciate ligament (ACL) reconstruction surgeries many patients wear a variety of knee braces with the intent to increase joint stability and prevent further injury. However, little is known about the neuromuscular effects of these braces during exercise among patients with ACL reconstructions. Therefore, Davis and colleagues completed a crossover study to compare quadriceps muscle activation (maximal contraction and central activation ratio [CAR]) among 14 patients with ACL reconstructions (9 women, 5 men) while they exercised wearing an off-the-shelf ACL functional brace, neoprene sleeve, or nothing on the knee. Patients were included if they had undergone a primary ACL reconstruction at least 2 years prior to all sessions. The patients attended a preliminary session to become familiar with the 20-minute aerobic exercise program (on a treadmill). After that session, the patients attended three sessions and performed the exercise protocol while wearing one of three bracing conditions: a knee brace, neoprene sleeve, or nothing (the order was randomized). The patients performed the quadriceps muscle testing (peak torque during maximal voluntary isometric contraction) 4 times: 1) baseline [before bracing condition or exercise], 2) before exercise but with bracing condition, 3) after exercise with bracing condition, and 4) after exercises with bracing condition removed. To measure the CAR, the patients performed a maximal isometric quadriceps contraction and when the examiner observed a plateau in the torque they triggered an electric stimulation of the quadriceps through electrodes placed on the thigh. This caused an increase in torque by activating the unrecruited portions of the quadriceps muscle. This was performed twice, separated by 30 seconds of rest. CAR is calculated as the maximal torque from the manual contraction divided by the maximal torque generated with the electrical stimulation. The authors found a reduction in maximal voluntary quadriceps contraction force but not CAR when comparing pre-exercise with bracing condition to baseline (braces showed the same pattern as not wearing a brace). The authors also reported a reduction in maximal voluntary quadriceps contraction and CAR during the post-exercise with bracing condition compared to the pre-exercise with bracing condition (once again, braces showed the same pattern as not wearing a brace). Finally, the authors noted that the maximal voluntary quadriceps contraction and CAR were lower during the post-exercise without the bracing condition compared to baseline; during which no one wore a brace. Overall, these findings demonstrated a decrease in quadriceps muscle function and activation following aerobic exercise. However, this finding was not influenced by the application of either a rigid knee brace or neoprene sleeve.

This study provides clinicians with an interesting look at quadriceps muscle recruitment when using various knee braces. While the findings suggest that wearing either a rigid knee brace or neoprene sleeve does not greatly diminish or promote quadriceps recruitment and activation, it is important to keep in mind that none of the data directly addressed knee stability or the perception of knee stability. This is something which would have been interesting to observe; especially since recent research has suggested that a fear of re-injury may be a barrier for some athletes to returning to previous levels of play. Wearing one of the braces may have led some participants to subjectively feel more stable with a brace. If this were true then perhaps bracing ACL-reconstruction patients would be greatly beneficial as it posed no further threat to quadriceps muscle function. If the opposite were true and patients felt no more stable than without a brace then this may lead clinicians to not recommend either type of brace as it would not benefit the patient. Tell us what you think. Do you recommend a brace following ACL reconstruction? What type of brace do you typically recommend?

Written by: Kyle Harris
Reviewed by: Jeffrey Driban

Related Posts:
Davis AG, Pietrosimone BG, Ingersoll CD, Pugh K, & Hart JM (2011). Quadriceps function after exercise in patients with anterior cruciate ligament-reconstructed knees wearing knee braces. Journal of Athletic Training, 46 (6), 615-20 PMID: 22488186


Kathleen White said...

I think this is an interesting study that unfortunately does not end the debate "To brace or Not to brace". In most cases it appears to be surgeon preference to either prescribe the brace or not and patient choice to wear it.

I agree that a further study that looks at knee stability, particularly during more dynamic tasks, may give us a better answer to the brace debate.

Kyle said...


Thanks for the comment. I believe that more dynamic tasks will unlock a much better understanding of this issue. I think another question that should be asked (and are seperate issues altogether) is why are those surgeons prescribing that specific brace and what factors affect the patient's decision to wear (or not wear) the brace. For now though I believe that the first step is understanding exactly how effective the brace itself is during dynamic activity.

William T. said...

As being a graduate assistant AT working with a D-I football program I’ve seen and dealt with a number of functional knee braces. I’ve actually been able to work closely with the offensive line that are all required to wear the DonJoy Defiance functional/prophylactic ACL knee brace. The braces are customized and fit by a DonJoy rep theoretically designed to fit and respond to the contours of each individual person. This past season there were no ACL or major ligament injuries experienced by those wearing said brace. There were a number of players who were ACL-R. I think this is a different situation given that the players were required to wear the braces however I’ve seen their effectiveness first hand; there have been times where there was a collision or we heard a loud crack or pop and once the pile and dust had cleared the athlete was fine however the brace was not. In other words the impact was so great that the brace had cracked or bent but the athlete’s knee was not damaged. I think given that there is enough funding at the University I have no issue against the requirement of wearing the braces. Obviously at other venues with less funding I think you run into more of an issue about recommending the DonJoy brace (typically runs $900).

I’ve read other research regarding the DonJoy Defiance brace and those studies addressed gastrocnemius musculature; I believe the results indicated a decrease in girth having worn the brace for a season however I’m not sure about MVIC and central activation results pre- and post-bracing. I’ve also talked to our team docs about other sports outside of football and the recommendation for the DonJoy Defiance brace or any functional knee brace following ACL-R and they’ve gone away from recommending any brace. I think due to the surgical technique and the current concepts of ACL rehabilitation have improved that the theory is that there is not a need for a brace as long as protocol is followed and the PT/ATC does a good enough job at restoring strength, stability and neuromuscular control. I think patient preference comes into play as well as sport since it’s a different situation with football offensive linemen who are all required to wear the brace, regardless of injury, as compared to lacrosse or basketball players in which they may be the only person wearing a brace out there. I think the requirement aspect as well as the type of motion required by a particular position in sport makes a difference as well. With offensive linemen who aren’t performing as dynamic change of direction movements as seen with lacrosse or basketball that require more explosive, quick, agile movements. It is my understanding that across the board with athletes the main concern with wearing a knee brace is that they feel they move slower or that their performance decreased as a result.

I agree with the points made by previous posts in that more research is needed with focus on dynamic tasks. I think I would be interesting to see how much movement actually occurs with bracing compared to no brace in functional tasks like pass blocking or rushing the passer or stopping on a dime. I think that will shed more light as to how effective the brace is. However I think that there won’t be a definitive solution that can be allocated across all athletics given that there are specific movement patterns associated with each sport as well as position.

Kyle said...


Thank you for the comment! You bring up some excellent points and I think from the points being raised we can say that those conducting future research in this area have a lot to consider. Firstly, I found your experience with the DonJoy Defiance brace fascinating. I would however, consider myself as one of the athletic trainers out there practicing at a institution (NJCAA; Jr. college)where I do not have the funding to mandate brace wearing but at the very least it is something that I can use when counseling my athletes.

Secondly, when thinking about future research, I agree with your points and suggestions as to where future research should look to explore. I think looking at the difference between sports and positions within a particular sport would be very beneficial. I also wonder if there would be a difference between athletes in different competition levels. For example is there a difference between injury prevalence in football centers at the division 1, 2, 3 or jr college level? Perhaps the caliber of athlete is also something to consider. Have you had experiences at other institutions that might shed some light on this question?

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