Accelerated versus standard rehabilitation after anterior cruciate ligament reconstruction: A systematic review and meta-analysis of randomized controlled trials

INTRODUCTION

Anterior cruciate ligament (ACL) rupture is a debilitating injury with an incidence of approximately 68/100,000 person-years in the United States.^[1,2] While ACL reconstruction (ACLR) remains the gold standard for restoring mechanical stability, the post-operative rehabilitation protocol is a critical determinant of successful graft integration and return to sport (RTS).^[3,4] Despite surgical advancements, re-injury rates remain concerning, necessitating a rigorous evaluation of post-operative management strategies.^[5]

Historically, “standard” rehabilitation prioritized graft protection through immobilization and delayed weight-bearing (WB). This conservative approach was driven by biomechanical concerns that aggressive mobilization would compromise graft integrity during the early phases of ligamentization.^[6] However, prolonged restriction has been linked to muscle atrophy and persistent range of motion (ROM) deficits.^[7] Consequently, “accelerated” protocols were introduced, characterized by immediate WB and early restoration of full extension. Pioneered largely by Shelbourne and Nitz, this paradigm hypothesizes that earlier mobilization reduces anterior knee pain and increases patient satisfaction without sacrificing stability.^[8]

The debate between these protocols centers on the tradeoff between knee laxity and functional recovery. Critics of accelerated rehabilitation cite concerns regarding increased anterior tibial translation; however, recent randomized trials suggest that early open kinetic chain (OKC) exercises do not result in significant differences in instrumented laxity compared to restrictive protocols.^[9,10] Conversely, standard rehabilitation is frequently criticized for resulting in extension deficits, which are strongly correlated with the development of arthrofibrosis and poorer long-term subjective outcomes.^[11,12]

Regarding patient-reported outcome measures (PROMs), evidence suggests that patients undergoing accelerated rehabilitation may achieve higher scores earlier in the recovery timeline due to reduced kinesiophobia and faster restoration of gait mechanics.^[13] Furthermore, achieving symmetrical ROM early in the post-operative period is a strong predictor of long-term knee health and patient satisfaction.^[14] Despite these findings, current literature often fails to comprehensively analyze the simultaneous interaction between PROMs and objective laxity, using meta-analytical methods. Therefore, this study evaluates the efficacy of accelerated versus standard rehabilitation following ACLR. We hypothesize that accelerated rehabilitation results in superior PROMs without a statistically significant increase in pathological knee laxity.

MATERIALS AND METHODS

RESULTS

Bibliometric search results

A total of 894 studies were identified based on the predefined search criteria. After the removal of 364 duplicates, 549 unique records remained for screening. During the initial screening phase, 526 records were excluded as they did not meet the inclusion criteria. The remaining 23 articles were assessed for eligibility through full-text screening, after which 12 studies were excluded for the following reasons: In three studies, the full text was not available; in nine studies, the patients were younger than 16 years. One study was identified through the Umeå University website. Ultimately, 12 RCTs were included in this SR.^[18-29] A detailed overview of the study selection process is presented in the PRISMA flow diagram [Figure 1], and the baseline characteristics of the included population are summarized in Table 1. The rehabilitation characteristics of each group are presented in Supplementary Materials Table 1. Across the included trials, accelerated protocols consistently allowed earlier full WB, more rapid progression of ROM, and earlier introduction of quadriceps strengthening (including OKC exercises where used), whereas standard protocols generally delayed these elements and followed more time-based progression criteria.

Supplementary Materials Table 1

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Figure 1:

Preferred Reporting Items for Systematic Reviews and Meta-analyses. Flow diagram of study selection. RCT: Randomized controlled trial.

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Table 1: Patient characteristics of the included studies.

Author	Publication Year	Origin	Journal	Group	Patient (n)	Age range	Mean age±SD	Male (n)	Female (n)	BMI±SD
Beynnon et al.[18]	2005	United States	The American Journal of Sports Medicine	Accelerated	10	18–44	30.4	5	5	23.5
				Standard	12	19–44	34.7	6	6	26.3
Beynnon et al.[19]	2011	United States	The American Journal of Sports Medicine	Accelerated	19	16–48	29.7	13	6	NR
				Standard	17	16–46	30.2	9	8	NR
Christensen et al.[20]	2013	United States	Journal of Sport Rehabilitation	Accelerated	15	NR	33.1±10.9	14	1	25.94±3.32
				Standard	15	NR	33.1±10.9	8	7	25.45±3.82
Ebert et al.[21]	2022	Australia	Physical Therapy in Sport	Accelerated	22	16–41	24.9±7.1	12	18	25.3±2.4
				Standard	22	16–42	25.7±7.9	19	21	25.1±3.3
Gupta et al.[22]	2017	India	Journal of Arthroscopy and Joint Surgery	Accelerated	20	NR	26.45±4.7	20	0	NR
				Standard	20	NR	28.90±6.3	18	2	NR
Jin et al.[23]	2022	China	Disease Markers	Accelerated	33	NR	29.06±6.96	19	14	22.67±2.51
				Standard	32	NR	29.90±6.48	20	12	22.88±1.96
Luo et al.[24]	2016	China	The Journal of Physical Therapy Science	Accelerated	20	NR	39.6±13.3	13	7	22.2±2.2
				Standard	20	NR	45.7±13.9	14	6	23.1±1.8
Mardani- Kivi et al.[25]	2024	Iran	Archives of Rehabilitation	Accelerated	42	NR	36	34	8	23.5
				Standard	43	NR	34	36	6	26.3
Patra et al.[26]	2022	India	Revista Brasileira de Ortopedia	Accelerated	40	18–60	34	37	3	24
				Standard	40	18–60	33	36	4	26
Svensson et al.[27]	2024	Sweden	Not published	Accelerated	78	NR	28.5±5.86	59	19	NR
				Standard	73	NR	28.9±6.41	49	24	NR
Yang et al.[28]	2025	China	The Journal of Sports Medicine and Physical Fitness	Accelerated	45	NR	35.4±9.6	21	24	24.2±5.6
				Standard	45	NR	32.7±9.8	18	27	24.2±5.2
Zhu et al.[29]	2013	China	European Journal of Orthopaedic Surgery and Traumatology	Accelerated	15	19–39	NR	NR	NR	NR
				Standard	15	19–39	NR	NR	NR	NR

BMI: Body mass index, NR: Not reported, SD: Standard deviation

Methodological appraisal of included studies

According to the current recommendations, the methodological quality of the included studies was assessed using the JBI Critical Appraisal Checklist for RCTs.^[30,31] The results of the critical appraisal are presented in Table 2. The assessment was conducted independently by two reviewers (M.H. and J.L.), and all extracted data and quality scores were subsequently verified by a third reviewer (R.P.) to resolve any discrepancies. Overall, the risk of bias was considered moderate across the included studies, with the most common limitation being the lack of blinding of participants and therapists, which is inherent to rehabilitation trials. This lack of blinding is particularly relevant for subjective, patient-reported outcomes because expectations regarding faster recovery in the accelerated groups and therapist–patient interactions may have influenced PROM responses.

Table 2: Quality assessment of all the included studies using the revised JBI critical appraisal tool for randomized controlled trials.

Meta-analysis

Knee laxity

The pooled analysis of anterior knee laxity, as measured by the KT-1000 arthrometer, included data from three studies at various post-operative time points. At 3 months postoperatively [Figure 2], there was no significant difference in knee laxity between the accelerated and standard rehabilitation groups. The pooled MD was 0.00 (95% CI −0.10 to 0.10, p = 0.97), with no evidence of heterogeneity (I² = 0%, p = 0.88). At 6 months [Figure 3], the analysis continued to show no significant difference between groups. The MD was 0.26 (95% CI −0.41 to 0.93, p = 0.44), with moderate heterogeneity observed (I² = 57%, p = 0.10). At the final follow-up of 12 months [Figure 4], the results remained consistent, with no significant difference in anterior knee laxity between the accelerated and standard rehabilitation protocols. The pooled MD was 0.06 mm (95% CI −0.31 to 0.42, p = 0.76), with low heterogeneity (I² = 39%, p = 0.18).

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Figure 2:

Forest plot of Anterior Tibial translation measured by the KT-1000 at 3-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 3:

Forest plot of Anterior Tibial translation measured by the KT-1000 at 6-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 4:

Forest plot of anterior tibial translation measured by the KT-100 at 12-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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PROMs

Functional outcomes were assessed using the International Knee Documentation Committee (IKDC) Subjective Knee Form, the Knee Injury and Osteoarthritis Outcome Score (KOOS), Lysholm Knee Scoring Scale, and the Tegner activity scale.

The pooled analysis of the IKDC subjective knee form included data from six studies at baseline and up to eight studies at various post-operative time points. The baseline (0 months), presented in Figure 5, shows no significant difference between the accelerated and standard rehabilitation groups. The pooled MD was 0.85 points (95% CI −0.19 to 1.89, p = 0.11), with no evidence of heterogeneity across studies (I² = 0%, p = 0.41). At 3 months [Figure 6] postoperatively, the accelerated rehabilitation group demonstrated numerically higher IKDC scores compared to the standard group. The pooled MD was 5.24 points (95% CI −1.09 to 11.57, p = 0.10), but this difference did not reach statistical significance and was accompanied by very high heterogeneity (I² = 98%, p < 0.00001), limiting the robustness of this finding. At 6 months [Figure 7], a similar non-significant trend was observed (MD 4.21 points, 95% CI −3.53 to 11.96, p = 0.29; I² = 99%, P < 0.00001). By the final follow-up at 12 months [Figure 8], there was no difference between the two rehabilitation protocols (MD −0.24 points, 95% CI −9.09 to 8.61, p = 0.96; I² = 99%, p < 0.00001), indicating that IKDC scores converged over time. By the final follow-up at 12 months [Figure 8], the difference between the two rehabilitation protocols was no longer in favor of the accelerated rehabilitation protocol. The pooled MD was −0.24 points (95% CI −9.09 to 8.61, p = 0.96), suggesting that while accelerated rehabilitation may facilitate earlier recovery, both groups achieve comparable functional outcomes at 1 year. Heterogeneity was also high at the final time point (I² = 99%, p < 0.00001).

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Figure 5:

Forrest plot of the International Knee Documentation Committee score at baseline. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 6:

Forrest plot of the International Knee Documentation Committee score at 3-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 7:

Forrest plot of the International Knee Documentation Committee score at 6-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 8:

Forrest plot of the International Knee Documentation Committee score at 12-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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The pooled analysis of the KOOS included data from three to four studies at various post-operative time points. Immediately following the surgical intervention [Figure 9], there was no significant difference between the accelerated and standard rehabilitation groups. The pooled MD was −0.51 points (95% CI −2.35 to 1.34, p = 0.59), with no evidence of heterogeneity (I² = 0%, p = 0.68). At 3 months postoperatively [Figure 10], the accelerated rehabilitation group demonstrated statistically significantly higher KOOS scores compared to the standard group, with a small pooled MD of 1.61 points (95% CI 0.90 to 2.31, p < 0.00001) and low heterogeneity (I² = 0%, p = 0.54). A statistically significant but similarly small MD of 0.78 points (95% CI 0.09 to 1.40, p = 0.03) was observed at 6 months [Figure 11], again with low heterogeneity (I² = 0%, p = 0.90) and at 12 months [Figure 12]. At the final follow-up of 24 months [Figure 13], a statistically significant difference in KOOS scores re-emerged in favor of the accelerated rehabilitation group (MD 1.18 points, 95% CI 0.39 to 1.97, p = 0.003; I² = 0%, p = 0.94), although the absolute magnitude of this difference was small.

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Figure 9:

Forrest plot of the Knee Injury and Osteoarthritis Outcome Score at baseline. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 10:

Forrest plot of the Knee Injury and Osteoarthritis Outcome Score at 3-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 11:

Forrest plot of the Knee Injury and Osteoarthritis Outcome Score at 6-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 12:

Forrest plot of the Knee Injury and Osteoarthritis Outcome Score at 12-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 13:

Forrest plot of the Knee Injury and Osteoarthritis Outcome Score at 24-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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The pooled analysis of the Lysholm knee scoring scale included data from four studies at various post-operative time points. At the pre-operative baseline [Figure 14], there was no significant difference between the accelerated and standard rehabilitation groups. The pooled MD was −0.26 points (95% CI −1.91 to 1.39, p = 0.76), with no evidence of heterogeneity (I² = 0%, p = 0.64). At 3 months [Figure 15] postoperatively, the accelerated rehabilitation group demonstrated higher Lysholm scores compared to the standard group, although this difference did not reach statistical significance. The pooled MD was 7.32 points (95% CI −5.04 to 19.67, p = 0.25). The heterogeneity was observed with I² = 100% (p < 0.00001). At 6 months [Figure 16], the accelerated group continued to show higher scores, but the difference was not statistically significant. The pooled MD was 8.81 points (95% CI −1.04 to 18.66, p = 0.08), with high heterogeneity (I² = 99%, p < 0.00001). By 12 months [Figure 17], the difference between groups narrowed and was not statistically significant. The pooled MD was 2.55 points (95% CI −3.96 to 9.06, p = 0.44), with persistent high heterogeneity (I² = 99%, p < 0.00001).

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Figure 14:

Forrest plot of the Lysholm score at baseline. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 15:

Forrest plot of the Lysholm score at 3-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 16:

Forrest plot of the Lysholm score at 6-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 17:

Forrest plot of the Lysholm score at 12-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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The meta-analysis of the Tegner activity scale included data from three to four studies at various post-operative time points. At the pre-operative baseline [Figure 18], there was no significant difference between the accelerated and standard rehabilitation groups. The MD was 0.09 points (95% CI −0.62 to 0.79, p = 0.81). High heterogeneity was observed (I² = 92%, p < 0.00001). At 3 months postoperatively [Figure 19], the analysis showed no significant difference in activity levels between groups. The MD was 0.04 points (95% CI −0.06 to 0.14, p = 0.44), with low heterogeneity (I² = 11%, p = 0.34). At 6 months [Figure 20], the accelerated group demonstrated slightly higher Tegner scores, although this difference did not reach statistical significance. The MD was 0.15 points (95% CI −0.03 to 0.33, p = 0.11), with no evidence of heterogeneity (I² = 0%, p = 0.49). At the final follow-up of 12 months [Figure 21], the accelerated rehabilitation group demonstrated significantly higher activity levels compared to the standard group. The MD was 0.76 points (95% CI 0.51 to 1.02, p < 0.00001), with no evidence of heterogeneity (I² = 0%, p = 0.62).

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Figure 18:

Forrest plot of the Tegner activity scale at baseline. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 19:

Forrest plot of the Tegner activity scale at 3-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 20:

Forrest plot of the Tegner activity scale at 6-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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Figure 21:

Forrest plot of the Tegner activity scale at 12-month post-operative. SD: Standard deviation, CI: Confidence interval. IV: Independent variable

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DISCUSSION

The most important finding of this SR and meta-analysis is that accelerated rehabilitation protocols following ACLR do not increase instrumented knee laxity compared with standard rehabilitation, supporting the safety of earlier WB and ROM exercises. PROMs showed small, and often statistically non-significant, early between-group differences favoring accelerated rehabilitation, with convergence of scores over time and substantial heterogeneity for several outcomes. Taken together, these data support the use of functional, criterion-based accelerated protocols as a safe alternative to traditional time-based regimens, while cautioning against overinterpreting modest group-level differences as definitive clinical superiority.

The primary hesitation regarding accelerated rehabilitation has historically been the risk of graft elongation due to early mechanical loading. However, our meta-analysis revealed no significant difference in anterior tibial translation between the accelerated and standard groups. The pooled analysis of KT-1000 arthrometer data confirmed no significant differences at any time point (3, 6, and 12 months), with the difference at final follow-up being negligible. This aligns with foundational biomechanical research. For instance, Fleming et al. demonstrated in vivo that anterior tibial translation strains the ACL graft significantly less during moderate WB activities compared to non-WB shear forces.^[32] This suggests that the physiological load applied during early full WB, when performed with proper gait mechanics, is well within the safety limits of modern fixation methods. Furthermore, McDevitt et al. showed early on that patients treated without bracing and with immediate WB did not exhibit increased laxity compared to braced, restricted controls, suggesting that the graft is protected by joint compression forces during WB.^[33] Consequently, the restriction of WB appears to offer no protective benefit to the graft while promoting muscle atrophy. As WB and other decisions can be influenced by concomitant injuries, the recently published meniscus rehabilitation consensus may help guide more precise recommendations.^[34,35]

One of the most significant advantages of accelerated rehabilitation identified in this study is the rapid restoration of function. Standard protocols that enforce immobilization or restrict extension frequently lead to anterior knee pain and extension deficits. By encouraging immediate full extension, accelerated protocols mitigate these risks. Jin et al. compared aggressive versus conservative rehabilitation and found that patients in the aggressive group not only maintained stability but also significantly outperformed the conservative group in isokinetic quadriceps strength at 3 and 6 months postoperatively.^[23] This early strength recovery is crucial, as quadriceps inhibition is a primary driver of altered gait mechanics and long-term joint degeneration. In addition, recent evidence regarding OKC exercises supports the safety of early loading. Heijne and Werner demonstrated in an RCT that starting OKC exercises as early as 4-week post-operative did not result in increased knee laxity compared to a late start (12 weeks) but significantly improved early quadriceps torque.^[36] This supports our finding that “accelerated” interventions, including early intensive muscle activation, are safe.

To fully understand the clinical relevance of these findings, a detailed examination of the specific domains captured by each PROM is necessary. The IKDC captures the domains of symptoms, sports activities, and daily function, serving as a global measure of knee-specific health. Our analysis showed that accelerated rehabilitation led to better scores in this instrument during the early post-operative period, indicating that patients achieve superior overall function and fewer symptoms in both daily and sports activities sooner than those following standard rehabilitation protocols. The Lysholm Knee Scoring Scale focuses primarily on symptom severity and functional status, specifically on instability and pain, which together account for half of the total score. The early improvements observed in the accelerated group within this domain suggest that these patients experience a greater subjective feeling of knee stability and less pain during activity at an early stage, which is critical because the sensation of giving way is a primary driver of activity limitations. The KOOS provides a broader picture by differentiating into five separate domains: Pain, symptoms, activities of daily living, sport and recreation function, and knee-related quality of life. The accelerated group demonstrated robust early benefits across nearly all of these domains, with the pain domain benefiting from the avoidance of immobilization-related consequences, the activities of daily living domain showing improvements in basic mobility, and improving athletic function through early loading. Remarkably, a significant advantage for the accelerated group reemerged at the 24-month follow-up, particularly within the quality-of-life domain, suggesting that the early normalization of the knee has a greater impact on long-term well-being. Finally, the Tegner Activity Scale, which exclusively measures the domain of activity level, revealed a distinct pattern. While early activity levels were similar between groups, by 12 months, the accelerated patients were participating in significantly higher-level sporting and occupational activities. This superior rate of RTS underscores that accelerated patients are not only feeling better but are also doing more, transitioning from basic activities to more demanding tasks like running on uneven ground or engaging in moderate labor. Nevertheless, when interpreted against published minimal clinically important difference thresholds for IKDC, KOOS, and Lysholm scores (typically around 8–11 points for IKDC and 8–10 points for several KOOS subscales, and approximately 5–6 points for Lysholm), many of the observed between-group MDs in our meta-analysis fall below or close to these cut-offs, suggesting that the clinical impact of statistically significant findings at the group level may be modest for individual patients. This pattern of early functional superiority and higher eventual activity levels is likely attributable to the psychological benefit of normalizing the knee early, which reduces kinesiophobia and reinforces a positive feedback loop of recovery where confidence and function build upon one another.

While our review focused on short- to mid-term outcomes, the safety of this approach is supported by long-term data in the broader literature. The Moon Knee Group reported on the 10-year outcomes of the accelerated protocol, noting that patients maintained normal stability and high subjective scores over a decade, without increased graft failure rates.^[37] This corroborates our conclusion that the early benefits in PROMs do not come at the cost of long-term joint integrity. The clinical implication is substantial: Preventing extension deficits and encouraging early mobilization are arguably the most critical factors in achieving long-term patient satisfaction and preventing osteoarthritis, rather than “protecting” the graft through immobilization.

This review is not without limitations. First, there was significant heterogeneity among the “standard” and “accelerated” protocols defined in the included studies. Although the core principles of accelerated rehabilitation consistently included earlier full WB, earlier restoration of full extension, and faster introduction of strengthening exercises, the exact timing and progression criteria varied across trials, which likely contributed to the clinical heterogeneity observed in the pooled PROM analyses and limits the generalizability of a single, uniform “accelerated” protocol. Second, the follow-up duration in many included RCTs was limited to 1 or 2 years. Finally, the lack of blinding in rehabilitation RCTs introduces a potential performance bias. While objective measures like KT-1000 laxity are less susceptible to such bias, patient-reported outcomes are particularly vulnerable, and some of the apparent advantages of accelerated rehabilitation in PROMs may reflect expectation and interaction effects rather than purely biological differences. Furthermore, clinicians should tailor these protocols based on concomitant injuries, which were excluded from most trials in this review.

CONCLUSION

Accelerated rehabilitation following ACLR does not result in increased instrumented knee laxity compared to standard rehabilitation, supporting the safety of earlier WB and ROM exercises. PROMs demonstrate small early between-group differences that generally diminish over time, and several comparisons did not reach statistical significance in the context of substantial heterogeneity. The current evidence therefore primarily supports accelerated rehabilitation as a safe alternative to standard protocols, with possible but not definitively established early functional advantages.