Functional Bracing After Anterior Cruciate Ligament Reconstructions: A Review of the Current Literature

Abstract

Anterior cruciate ligament (ACL) injuries are increasingly common in pediatric and adolescent athletes, driven by rising participation in high-risk sports. Functional knee bracing (FKB) has been proposed as a strategy to reduce both initial injuries and reinjuries following ACL reconstruction (ACLR). The current review examines biomechanical and clinical evidence related to the use of FKB status post-ACLR, focusing on its potential in preventing ACL re-injury. Biomechanical studies suggest that FKB may reduce abnormal knee movements in controlled conditions, specifically anterior tibial translation. However, results are inconsistent on preventing injury-inducing movements or mechanisms in the knee when assessed as part of dynamic testing. Clinically, the small number of relevant comparative studies analyzing braced versus nonbraced cohorts show heterogeneous results, with mixed conclusions on whether FKB effectively reduces ACL re-tear rates. There are several understudied aspects associated with FKB, leaving surgeons without definitive recommendations regarding key factors, such as the optimal brace type, the impact of graft type, appropriate timing and duration of brace wear, compliance challenges, and the psychological and proprioceptive effects of bracing on patients. Given the conflicting evidence and lack of definitive existing guidelines, the role of FKB for patients returning to high-risk activities after ACLR currently remains uncertain, underscoring the need for higher-quality research to guide clinical practice, particularly for the highest risk sub-populations of pediatric and adolescent athletes.

Key Concepts

• (1)Functional knee braces have been shown to reduce anterior tibial translation in controlled conditions but show inconsistent effects on rotational forces and valgus stability during dynamic activities.
• (2)Clinical studies offer conflicting evidence on the effectiveness of functional bracing in reducing ACL re-tear rates, with no consensus on routine use.
• (3)Patient-specific factors, including graft type, compliance, and baseline knee stability, may influence the effectiveness of functional bracing.
• (4)Psychological benefits, such as reduced fear of reinjury, may contribute to the value of bracing, though effects on proprioception and muscle strength are mixed.
• (5)Further research is needed, particularly with dynamic, sport-specific testing, to determine the true efficacy of functional bracing in ACL reconstruction recovery.

Introduction

The anterior cruciate ligament (ACL) is the most frequently injured ligament in the knee, responsible for nearly half of all knee injuries requiring surgery [1]. In the United States, approximately 1 in 3,500 people sustains an ACL injury each year, resulting in about 400,000 ACL reconstructions (ACLR) annually [1,2]. Children and adolescents are especially prone to ACL injures, with an incidence of up to 51 in 100,000 [[3], [4], [5]]. Rates in this population are likely higher than those of their adult counterparts due to higher baseline activity levels, as well as increasing participation in intensive sports training and specialization at increasingly younger ages. Rates of ACL tears are also increasing more quickly in pediatric and adolescent cohorts compared to adult cohorts, at a rate of 2%–3% per year [3,4,6]. Additionally, this vulnerable patient population is at higher risk for ACL graft rupture (ie, ACL retear) postoperatively, with recent studies showing rates as high as 35% [[7], [8], [9]]. The normal reinjury rate is amplified 4-fold when patients are re-exposed to level I sports—activities involving cutting, pivoting, and jumping [10]. As a result, athletes, their families, and sports surgeons— as well as coaches, physical therapists, athletic trainers, sports psychologists and many others— have a common interest in reducing index ACL tears and retears, especially in young, active children, and adolescents.

Bracing has been proposed as a potential intervention to lower ACL injury rates, both index tears and retears, while allowing patients to participate in high-risk sports. Theoretically, bracing guards against excessive varus-valgus forces and prevents supraphysiologic anterior-posterior translation and/or rotation at the knee joint. Numerous types, makes, and models of braces exist. Braces are most often categorized by their intended use as: (1) prophylactic, (2) rehabilitative and (3) functional. Prophylactic braces are those designed to prevent or reduce the severity of knee injuries in athletes and are often worn before an index injury has occurred. Rehabilitative braces are utilized in the early postoperative period. They tend to be simple hinged knee braces designed for extra support or protection, particularly in the setting of a concomitant meniscus repair. While more commonly used, rehabilitative braces likely have little impact on ACL retear rates as they are used during a time of relatively low risk of reinjury. Thus, rehabilitative braces will also not be discussed in this review, which will instead focus on functional braces.

Functional bracing aims to more specifically safeguard an injured knee or a reconstructed knee with an ACL graft and are worn for higher-level functions, ie, cutting and pivoting sports. They are specifically rigid and hinged, with both off-the-shelf and custom-fitted models available (Fig. 1). These braces are designed to minimize excessive forces which may contribute to ACL tears and graft failures, as outlined in Fig. 2. More recently, some braces have been designed to provide increasing resistance with increasing extension, thus restricting hyperextension. Others use a dynamic tensioning cable to exert directional forces on the femur and tibia to reduce translation (Fig. 1D) [11]. In addition to variation in the type of functional brace used, there is also significant variability in the practices of surgeons as it relates to the timing or duration of bracing. Furthermore, not all surgeons recommend functional braces for returning to high-risk sports after ACLR. In a recent survey study of orthopaedic surgeon-members in the American Orthopaedic Society for Sports Medicine, 63% of surgeons who perform ACLR routinely recommend the use of functional braces when retuning to sport, whereas 13% of responders never brace ACL-reconstructed patients [12]. Among members of the Pediatric Research in Sports Medicine (PRiSM) Society caring for pediatric and adolescent patients with ALC tears, only 50% recommended functional bracing upon resumption of unrestricted sports participation after ACLR [13].

Figure 1.

A variety of functional anterior cruciate ligament braces are available, including off-the-shelf models such as the CTi3 brace (A) and custom models such as the A22® (B) and Rebound® (C) braces. Some braces, such as the Rebound©, include dynamic tensioning cables (D), which further accentuate anterior forces applied to the femur and posterior forces applied to the tibia. Photos courtesy of Össur (A, C, and D) and Donjoy (B). Photos courtesy of the brace manufacturers-- Össur (images A, C and D) (Irvine, CA, USA) and Donjoy (image B) (Carlsbad, CA, USA).

Figure 2.

Functional anterior cruciate ligament (ACL) braces are designed to resist excessive forces which put a native or reconstructed ACL at risk of injury, including anterior tibial translation (points A-D), knee valgus (1), and hyperextension (2). Figure by Aimee Son, MS, CMI. Copyright ©2025 COSF.

Despite the prevalence of bracing, there is limited and conflicting evidence regarding its effectiveness in preventing injury when used for return to sport after ALCR. This lack of a clear scientific consensus presents a significant challenge, leaving both patients and healthcare providers without definitive guidance in this very common clinical scenario. Given conflicting practice patterns and the high stakes involved, the current review aims to more deeply and comprehensively explore the existing literature surrounding functional bracing after ACLR. Biomechanical and clinical studies were reviewed, along with additional psychological, social, and treatment variable considerations, to provide a comprehensive overview of our current understanding regarding the role of functional bracing in return to sport and reinjury prevention.

Biomechanical studies of functional bracing

The modern rigid functional ACL brace is theoretically designed to prevent extreme movement patterns typically associated with an acute ACL injury. Specifically, ACL ruptures occur when there is excessive translational force across the knee in the sagittal plane, in which the tibia moves anteriorly relative to the femur, or excessive rotational force in the transverse or axial plane, in which the tibia rotates externally relative to the femur (or, more pointedly, the femur rotates internally relative to the fixed tibia). Finally, there may also be a component of biomechanical alteration in the coronal plane, in which the knee moves into excessive valgus. The degree to which different biomechanical studies, both kinematic and kinetic in nature, have elucidated the effects of braces on preventing such injury-related movements is quite variable. Of note, while the majority of studies have investigated rigid hinged knee braces typically prescribed for sports, there are also a number of studies investigating the effects of soft braces or simple hinged knee braces. A systematic review covering the biomechanical effects of prophylactic bracing inclusive of these less rigid braces has been previously published by Tuang et al. [14] However, as these braces are typically prescribed during rehabilitation rather than during return to sports following ACL reconstruction, the biomechanical results related to these soft or simple hinged braces will not be included in the current review. Biomechanical studies have also varied between cadaveric and in vivo studies, with patient-based studies including subjects who are status post-ACLR, ACL deficient, or uninjured patients. Investigations with all three types of subjects are presented here.

Rotational forces

Several studies have demonstrated that functional ACL braces may be protective against excessive rotational forces. Beynnon et al. found that functional bracing notably reduced strain values on the ACL in response to internal-external torque (6 N∗m) of the tibia in non-weight bearing conditions [15]. Additionally, Yeow et al. found that a brace prototype with an anterior-sloped joint significantly reduces axial tibial rotation during landing [16].

Other studies, however, presented contrasting findings. Fleming et al. assessed forces up to a 9 N moment and found that bracing reduced strain only during internal torque (relative to the femur) in non-weight bearing knees, but not during external torque or in any weight bearing conditions [17]. Paradoxically, in a study by Focke, rigid knee braces were shown to actually increase transverse plane range of motion and increase the peak internal rotation angle [18]. Additionally, a cadaveric study by Hacker et al. found that functional bracing did not significantly affect ACL strain or kinematics during internal or external moments [19].

The variability in outcomes across studies suggests that while functional knee braces may hold promise in mitigating rotational forces, their effectiveness, if present, likely depends on patient-specific factors and design-specific features. Future studies should focus on multiplanar assessments that include real-world rotational demands, such as rapid changes in direction during cutting in soccer or pivoting in basketball, to clarify whether braces can effectively reduce ACL retear risk in high-intensity rotational scenarios.

Translational forces

The effectiveness of functional braces in reducing forces in the sagittal plane has been more extensively studied. Significant evidence indicates that functional knee braces effectively reduce anterior tibial translation, with Wojtys et al. specifically reporting reductions of approximately 30%–40% without muscle activation and 70%–85% with muscle activation [16,20,21]. Additionally, DeVita et al. demonstrated that one brace model provided a decrease in translational loads protective of the ACL graft in a series of patients after reconstruction, as well as findings that suggest functional bracing causes unique power patterns (altered extensor torques and muscle activation) that lead to knee protection [[22], [23], [24]]. However, because these findings were limited to changes detected in walking patients, most of the benefits may be due to neuromuscular adaptations associated with walking. Notably, when the same testing was applied to running patients, the results were not replicated. DeVita similarly found no significant differences in braced vs. nonbraced conditions in joint moments of force in an earlier study that also included running patients [25].

Two studies by Hangalur et al. and Rishiraj et al. investigating landing mechanics found that braces lower ground reaction force (GRF), while studies by Yeow and Ewing showed no effect of bracing on GRF [16,[26], [27], [28], [29]]. Importantly, Beynnon et al. found that while bracing does decrease abnormal anterior tibial translation during both non-weight bearing and weight bearing conditions independently, it failed to normalize such movements during the transition from non-weight bearing to weight bearing. Such findings may explain why braced ACL-deficient patients may continue to experience abnormal knee translations during dynamic activities, such as jumping and landing [20]. While functional knee braces demonstrate significant reductions in anterior tibial translation, particularly in controlled settings, their effectiveness in managing high-translational force scenarios like jumping, landing, and sprinting remains uncertain, underscoring the necessity for more sport-specific testing.

Varus/valgus forces

Preventing transient excessive genu valgus during cutting, pivoting, and landing may be critical to reducing strain on the ACL graft and minimizing the risk of retear. Lu et al. demonstrated reductions in varus/valgus bilateral kinetic asymmetry between the reconstructed and contralateral normal knees when ACLR subjects wore functional braces postoperatively [30]. Additionally, Beynnon et al. demonstrated that rigid braces reduce the maximum valgus angle when compared to no brace [15]. Conversely, studies by Butler and Dai found that knee varus/valgus asymmetry was not influenced by the use of functional bracing [31,32]. Moreover, Flemming et al. found that bracing did not affect strain in varus and valgus moments (10 N∗M) [17]. The series of conflicting findings in studies investigating coronal plane forces are particularly confusing, given the high rates of football linemen that wear functional braces specifically to avoid injuries secondary to excessive varus/valgus forces. However, because the included studies were more focused on the limit of forces relevant to the ACL, rather than the extreme forces needed to generate collateral ligament injury, the clinical relevance or takeaways of such studies may not extend to all of their clinical uses.

Summary of biomechanical studies

In the somewhat limited series of biomechanical studies available, heterogeneous studies on functional ACL bracing show at times potential benefits and at other times a lack of benefits, limiting the ability to draw definitive conclusions on its efficacy. The variability in outcomes suggest that while functional knee braces may hold promise in mitigating forces across the ACL, their effectiveness, if present, likely depends on patient-specific, brace design-specific, and activity-specific features. Out of the 17 studies reviewed, 16 reported some form of positive effect from functional bracing, primarily in limiting abnormal movements within the knee. However, nearly all of these studies either did not involve dynamic testing (instead focusing on low-level forces more representative of activities of daily living), had negative findings in terms of the effectiveness of the brace, or observed a decrease or disappearance of the positive effects when higher level functional testing was investigated. The current body of research lacks dynamic testing which replicates or represents the full physical and mechanical demands of many sports to which patients, especially young athletes, aspire to return. This approach is particularly important, as some studies suggest ACL tears are more likely to occur during multiplanar rather than uniplanar mechanisms of injury [33]. These findings highlight the need for future studies to incorporate multiplanar assessments and complex movement patterns to better simulate real-world stopping/starting, cutting/pivoting, and jumping/landing scenarios that more accurately replicate sports activity. With ever-improving testing technology and analytical tools, such as 3D motion analysis and computer simulation, many opportunities exist to better investigate the independent effect of functional braces and patients’ accommodations to them. Future research, therefore, should include standardized study protocols agreed upon by the community of biomechanical researchers, incorporate larger sample sizes, and consider more diverse activities and patient demographics to better understand the nuanced effects of functional knee braces.

Other biomechanical considerations

There are several other important influences that functional braces may have on patients returning to sport after ACL reconstruction, including proprioception, muscle strength, and limb symmetry. Studies investigating whether bracing may enhance knee or limb proprioception are mostly negative. For instance, Birmingham et al. found that while bracing provided small improvements in proprioception and postural control during tasks with limited somatosensory demands, these benefits did not extend to tasks with increased somatosensory demands [34]. Additionally, two studies found that bracing did not improve functional performance and may even slow reaction times in ACLR patients [35,36]. Similar results are illustrated with muscle strength, where long-term studies show unchanged or negative results in braced vs nonbraced patients [37]. For example, Risberg et al. found significant weakness in the quadriceps for patients wearing their braces for a period greater than one year [38]. On the other hand, both positive and negative results have been reported for the role of functional bracing in improving limb symmetry with functional testing in ACLR patients. In a study by Peebles el al, symmetry improved with functional knee bracing (FKB) during early return-to-sport hop testing, while Goodstadt et al. found better performance without the brace one year status post-ACLR [39,40]. Dai et al. also noted that limb asymmetries persisted during cutting activities with FKB, suggesting short-term hop test improvements may not translate to functional movements [32].

An additional factor worthy of mention, but even more difficult to study, is the potential influence of a psychological benefit of bracing. One study that indirectly explored this effect found that knee bracing and kinesio-taping may improve function after ACLR, but knee bracing offered greater benefits in reducing kinesiophobia [41]. A separate study by Wu et al. tested the sensorimotor performance of ACLR subjects with a normal brace, a placebo brace, and no brace, where both the normal and placebo brace preformed similarly better than the nonbraced group [42]. Furthermore, one study found that functional braces could reduce ACL strain during dynamic activities in high-risk subjects, primary due to enhanced muscle firing patterns associated with brace wear [28]. These suggest that both physiological and psychological effects of bracing may have an impact, with ALCR patients having an enhanced perception of their knee function or safety with bracing, which may encourage more typical and less injury-prone movements.

Clinical studies of functional bracing

A wide range of clinical measures are important to consider when evaluating the efficacy of functional bracing. Graft retear rates and (re)injury of the menisci and/or cartilage are typically of utmost concern. Stability metrics (such as the Lachman test, pivot-shift test, and KT1000 knee arthrometer values), performance metrics (such a single-leg hop tests and isokinetic strength testing), and finally patient-reported outcomes (PROs) (such as the International Knee Documentation Committee (IKDC-2000) and Lysholm scores) are also important to consider. However, not only do few studies utilize this wide a range of outcome measures, but there are remarkably few studies overall that have addressed the clinical efficacy of functional bracing in a methodologically rigorous fashion. Four studies worthy of detailed review are summarized in Table 1 and will be discussed in detail.

Table 1.

Summary of clinical evidence on functional bracing after ACL reconstruction.

Study	Population	Bracing Protocol	Key Findings
Sterett et al.	820 ski resort employees	Self-selected brace use during ski season	Braced skiers had lower reinjury rates (4% vs 9%, P = .009). No significant difference in ACL revision (0% vs 2%).
McDevitt et al.	95 military cadets	6 months of functional bracing for activity	No significant difference in reinjury rates or functional outcomes.
Perrone et al.	275 adolescent athletes	Braced vs nonbraced return to sport as standard of care in 2 geographic cohorts	Lower graft reinjury (10% vs 21%, P = .028) but also lower return-to-sport rate (63% vs 88%) in the in braced vs nonbraced group
MARS study group	695 revision ACLR patients	30% prescribed functional brace	No statistically significant difference in graft failure (20% vs 30%, P = .23). Braced group had better KOOS scores.

ACL, anterior cruciate ligament; ACLR, ACL reconstruction; KOOS, Knee Injury and Osteoarthritis Outcomes Score.

The most often cited study, by Sterett et al. evaluated the use of ACL functional braces by employees at a major ski destination from 1991 to 1997 [43]. Eight hundred and twenty employees with prior ACL reconstructions were identified and referred to the staff physician to discuss functional bracing. Thirty-six percent of subjects then self-selected to use a brace for the ski season. Interestingly, this cohort had more laxity at baseline, with 29% having a >1+ Lachman as compared to 11% in the cohort who chose not to brace, perhaps suggesting some perceived stability from bracing. Workers’compensation claims were used to track reinjury rates over the 6-year period. The braced skiers had a reinjury rate of 4%, which was statistically significantly lower than the 9% reinjury rate in nonbraced skiers (P = .009). Operative injuries occurred in 1% of braced and 4% of nonbraced skiers, while revision ACLR occurred in 0% and 2%, respectively (P = .11). Overall, injured skiers had more baseline ACL graft laxity than their noninjured counterparts, though this only reached statistical significance in the nonbraced cohort. Because of the increased risk of subsequent injury in the nonbraced cohort, the authors recommended bracing for skiers after ACLR. However, this was not a randomized nor a controlled trial. A skier's choice to brace may have been influenced by perceived (in)stability, and indeed this baseline stability may confound or contribute to retear rates.

Thus far, only one randomized controlled trial has evaluated functional bracing [37]. This study by McDevitt et al. randomized 95 cadets and midshipmen with ACL tears enrolled in 3 US service academies with ACL tears into braced vs nonbraced groups after bone-tendon-bone ACLR. All subjects wore a rehabilitative brace for 3 weeks postoperatively, and the braced group continued to wear the rehabilitative brace for an additional 3 weeks. The braced group then transitioned to a functional knee brace, which they wore daily for 6 months and for all rigorous activity up to 1 year after surgery. Both cohorts followed the same postoperative rehabilitation protocol and were followed for a minimum of 2 years. Results showed that 2 (4%) braced and 3 (6%) nonbraced subjects experienced significant injuries to their knees, although only 1 (2%) braced and 2 (4%) nonbraced subjects had full or partial ACL tears. There was no statistically significant difference in injury rates, range of motion, prone heel height, isokinetic testing, single-leg hop for distance, Lysholm score, KT1000 arthrometer measurements, IKDC-2000 scores, Lachman test, pivot-shift test, radiographic findings, or brace-related questionnaire responses between the braced vs non-braced groups. In this homogenous, athletic population, functional bracing after ACLR did not significantly improve any of the studied clinical measures, though with relatively short-term bracing of 1 year and short-term follow-up of 2 years.

Another critical study evaluated the effectiveness of functional bracing specifically in the most at-risk patient population for retears—athletic adolescents. Perrone et al. compared a single-surgeon cohort of 135 adolescents in the United States who used a functional brace for postoperative return to sport to a historical control cohort of 140 adolescents in Australia who had not used a functional brace for return to sport [44]. At an average follow-up of around 5 years in both groups, 10% of patients in the braced cohort experienced a graft injury, compared to 21% in the nonbraced cohort. Contralateral ACL injury occurred in 13% of braced patients, compared to 12% of nonbraced patients. However, it should be noted that only 63% of braced patients returned to cutting and pivoting sports, as compared to 88% of unbraced patients. While this study supports functional bracing in this high-risk population, there were significant differences between the cohorts regarding patient demographics, specific surgical techniques, and rehabilitation protocols.

Finally, a multicenter study performed by the Multicenter ACL Revision Study (MARS) revision ACLR study group examined the utility of functional bracing for patients who underwent revision ACL reconstruction. Six-hundred ninety-five patients were followed for 2 years postoperatively, and 30% of these patients were prescribed functional braces for return to sports. Patients who were prescribed an ACL functional brace had better scores on the Knee Injury and Osteoarthritis Outcomes Score (KOOS) sports/recreation subscale at 2-year follow-up, with similar Marx activity levels between braced and nonbraced patients. Patients who were prescribed a functional brace for return to sports had a lower-than-expected frequency of graft failure (20% vs. 30%), but this difference was not statistically significant (P = .23). Thus, the authors concluded functional bracing had no effect on graft failure rates after revision ACLR [45].

Other clinical considerations

There is a myriad of additional factors that may influence the heterogeneity between clinical results of different studies and must be considered when evaluating conclusions or recommendations related to the efficacy of functional bracing. First, there are important differences in the types of braces used across clinical studies. Some studies, such as McDevitt et al., prescribed only off-the-shelf braces, while other research does not differentiate between off-the-shelf and custom-fitted braces. Dynamic bracing is a newer option, though much of the research remains industry-driven [11].

The type of graft used in ACL reconstruction may also play a role. Studies such as those by McDevitt et al. and Perrone et al. have focused on specific graft types to ensure comparability. However, this does not elucidate whether patients with certain graft types might benefit more than others from functional bracing. For example, bone-patellar tendon-bone (BTB) grafts have been shown in several studies to have lower retear rates than hamstring grafts; it is unclear if benefits of functional bracing are more pronounced after hamstring ACLR in the study by Perrone et al. as compared to after bone-tendon-bone ACLR in the study by McDevitt et al., because of the graft choice or because of other study design factors. Studies with mixed grafts may provide more generalizable results but must be adequately powered. Timing and duration of bracing may be another influential factor in its effectiveness. McDevitt et al. braced patients for only one year postoperatively, though graft maturation can continue for up to 2 or 3 years [46,47]. Most patients aren't cleared for high-risk sports until 9–12 months postoperatively, making it unclear whether bracing for just one year offers optimal protection. Similarly, Perrone et al. found that retears commonly occurred after the two-year postoperative mark, when bracing was no longer mandatory [44]. Overall, there remains no definitive recommendation for when and for how long functional braces should be prescribed.

Compliance with brace use represents yet another challenge. In the study by Perrone et al. only 54% of patients were wearing their braces at the time of reinjury, though again, some patient may have been past the recommended length of postoperative brace use. In the study by McDevitt et al., even within the more structured environment of a military academy, 21% of patients were noncompliant with brace wear. Some patients reported a sense of security while wearing the brace, while others had complaints concerning the fit, slippage, and negative effects on sport performance, stating that they felt the brace wasn't needed. When considering adolescents, compliance may vary widely. In some populations or environments, it might be higher, due to increased oversight from parents and coaches, who may enforce brace use during activities. However, lower compliance may instead stem from a lack of understanding of the long-term benefit among adolescents, who may perceive bracing as uncomfortable or unnecessary. Patient and family preferences may also play a role in decision-making. Although large studies may show minimal benefit, individual patients may perceive any potential reduction in retear risk as worthwhile. Many patients see the brace as a reminder of their injury and as an essential part of their recovery process, even if the statistical benefit is thus far less clear.

Finally, functional bracing for ACL injuries imposes a substantial financial burden on healthcare systems, averaging $592 USD per case. Off-the-shelf braces can cost several hundreds of dollars. However, may patients complain of fit and comfort issues with off-the-shelf braces, electing for custom versions which can cost over $1,000, often paid out-of-pocket. This price can be difficult for families to afford on top of surgery and rehabilitation costs. The study by McDevitt et al. cited an estimated $90,000 spent annually on functional bracing for service academies, highlighting the potential economic impact of routine brace use [37]. In the USA and Scandinavia alone, this translates to an estimated annual cost exceeding $65,000,000 USD [48]. The critical question remains whether functional bracing can provide positive effects in lowering rates of reinjury, particularly ACL graft rupture. Even a marginal statistical benefit would likely justify the costs and effort associated with bracing if it avoided subsequent surgeries. Conversely, if functional bracing were shown to have absolutely no benefit, eliminating this common clinical practice could result in cost savings, minimize unnecessary variation in care, and allow athletes to focus on other aspects of their rehabilitation such as neuromuscular programs, proprioception, and psychological recovery.

Summary

Despite the prevalence of functional bracing, there is limited and conflicting evidence regarding its effectiveness when used after ACL reconstruction. There are additional arguments for and against widespread functional bracing as outlined in Table 2. While functional braces are designed to mitigate excessive forces that may contribute to ACL reinjury, specifically excessive anterior tibial translation, rotation, and valgus angulation, there is incomplete kinematic and kinetic evidence to support whether they perform all aspects, or the key aspects, of this intended biomechanical function. Studies do suggest that braces limit anterior tibial translation, particularly in low impact, controlled conditions. However, their effectiveness in dynamic activities and multiplanar movements is less supported. Furthermore, some studies note deleterious effects of functional bracing on proprioception and reaction times. Clinical evidence supporting the efficacy of functional bracing is similarly heterogenous. Only four studies have compared braced versus unbraced cohorts returning to sports and activities. The only randomized controlled trial showed no difference in retear rates with FKB [37,48]. However, this study is somewhat limited in sample size, length of brace wear, and length of follow-up. Two larger though less controlled studies did show reductions in reinjury rates but had significant differences in baseline characteristics between the braced and nonbraced groups [43, 44]. It is highly possible that higher risk populations, including children and adolescents returning to high-risk sports, and those with more knee laxity postoperatively–benefit the most from functional bracing after ACLR. However, the current evidence does not provide enough support to make definitive recommendation for or against routine functional bracing---not in specific patient populations nor in all patients after ACLR. Unequivocally, the subject has been incompletely explored. The sparse and heterogeneous nature of current evidence highlights the necessity for renewed high-quality research on if, how, and when functional bracing can benefit patients as they return to sports after ACL reconstruction, particularly the youngest patients at greatest risk of re-injury.

Table 2.

Pros and cons of functional bracing after ACL reconstruction.

Potential pros	Potential cons
May reduce anterior tibial translation in controlled conditions	No strong evidence that bracing prevents ACL re-tear in dynamic, high-risk activities
Provides psychological confidence, potentially reducing fear of reinjury	May impair proprioception and reaction times, affecting neuromuscular control
May help improve limb symmetry during early functional testing	No consistent benefit in functional performance tests, eg, hop tests or agility drills
Some studies suggest lower re-injury rates in adolescents and skiers	Compliance issues—athletes may stop wearing brace, due to discomfort, fit, or performance concerns
May promote altered muscle activation patterns that could reduce strain on the ACL	High cost of item and orthotist charges, especially for custom braces, with inadequately investigated cost-benefit ratio

ACL, anterior cruciate ligament.

Additional links

• •Clinical Journal of Sport Medicine:Biomechanical Effects of Prophylactic Knee Bracing on Anterior Cruciate Ligament Injury Risk: A Systematic Review.
• •The American Journal of Sports Medicine:Functional Bracing after Anterior Cruciate Ligament Reconstruction: A Prospective, Randomized, Multicenter Study.
• •Orthopaedic Journal of Sports Medicine:Risk of Secondary ACL Injury in Adolescents Prescribed Functional Bracing After ACL Reconstruction.

Consent for publication

The author(s) declare that no patient consent was necessary as no images or identifying information are included in the article.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author contributions

Charles R. Heyworth: Writing – original draft, Methodology, Investigation, Conceptualization. Lauren E. Berube: Writing – review & editing, Supervision, Investigation, Conceptualization. Emma C. Gossman: Writing – review & editing, Supervision, Resources, Project administration. Matthew D. Milewski: Writing – review & editing, Supervision, Conceptualization. Elise C. Bixby: Writing – review & editing, Writing – original draft, Supervision, Methodology, Investigation, Conceptualization.

Declaration of competing interests

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Elise C. Bixby, MD received educational payments from Arthrex Inc. and Smith and Nephew Inc. Matthew D. Milewski, MD receives royalties from Elsevier and is on the Board of Directors for PRiSM. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.