Research Review By Dr. Joshua Plener©


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Date Posted:

January 2023

Study Title:

Rehabilitation after anterior cruciate ligament and meniscal injuries: a best-evidence synthesis of systematic reviews for the OPTIKNEE consensus


Culvenor A, Girdwood M, Juhl C, et al.

Author's Affiliations:

La Trobe Sport and Exercise Medicine Research Centre, School of Allied Health, Human Services and Sport; La Trobe University, Australia; Department of Sports Science and Clinical Biomechanics, University of Southern Denmark; Department of Physiotherapy and Occupational Therapy, Copenhagen University Hospital, Denmark

Publication Information:

British Journal of Sports Medicine 2022; 56(24): 1445-1453. doi: 10.1136/bjsports-2022-105495.

Background Information:

ACL and meniscal tears are the most common traumatic knee injuries in athletes (1, 2). Often, surgery is performed to repair the tear in order to restore mechanical stability, facilitate return to competitive sport and prevent secondary injury (3). However, two-thirds of patients don’t return to pre-injury level within the following year post ACL reconstruction and approximately 25% sustain a second ACL injury (4). In the long term, patients commonly report knee symptoms, as well as functional deficits and impaired quality of life (5, 6). Furthermore, half of injured individuals will subsequently develop symptomatic knee osteoarthritis within 10 years, regardless of undergoing operative or non-operative treatment (7, 8).

Clinical practice guidelines emphasize the importance of active rehabilitation following an ACL injury and reconstruction in order to restore muscle strength and lower limb function, reduce pain and symptoms, and safely return to competitive sport without reinjury (9). However, there is little consensus on the optimal components of ACL rehabilitation, reflecting a lack of evidence and substantial heterogeneity in rehabilitation protocols (9, 10). The aim of this systematic review was to critically appraise and synthesize systematic review evidence of RCTs evaluating rehabilitation interventions following ACL or meniscal injury to improve symptomatic, functional, clinical, psychosocial or quality of life outcomes and prevent reinjury.

Pertinent Results:

Literature Search and Study Characteristics:
Twenty-two systematic reviews including 142 RCTs were included in this review. The reviews were published between 2004 and 2021 and focused mainly on ACL injury and reconstruction populations. The number of individual trials evaluating the same intervention ranged from 3 to 13, with a total number of participants randomized ranging from 98 to 789.

The most common interventions evaluated in the reviews were neuromuscular electrical stimulation, open versus closed kinetic chain exercises, cryotherapy, structured in-person versus structured home-based rehabilitation, whole body vibration, and neuromuscular control exercises. Single reviews evaluated the effect of preoperative rehabilitation, psychological interventions, blood flow restrictive training, knee braces, dietary supplements and continuous passive motion. Six of the 22 reviews were rated as high or unclear risk of bias across all four domains and were subsequently excluded from data synthesis.

Neuromuscular Electrical Stimulation (NMES):
Four reviews assessed this intervention and moderate certainty evidence indicated a large effect size for the addition of neuromuscular electrical stimulation at 2 to 6 sessions per week compared to standard rehabilitation for improvements in quadriceps strength in the first 4-12 weeks postoperative. There was very low to low certainty evidence from two reviews indicating that NMES in the first 2 post-operative months resulted in greater self-reported and physical function immediately following the period of application. The number of treatment sessions and electrical parameters are widely variable across RCTs, with no consistent dose-dependent effect noted.

Open Kinetic Chain Exercises:
Three reviews assessed open versus closed kinetic chain exercises and found no significant difference in measures of knee laxity, muscle strength, self-reported and physical function between the two approaches at any follow-up time point. There is moderate certainty evidence from the most recent review indicating no difference in knee laxity and quadriceps strength in the short term, self-reported function in the long term and rate of adverse events within the first 2 years.

Structured In-Person Rehabilitation:
Two reviews evaluated structured in person rehabilitation versus structured home based rehabilitation following ACL tear and reconstruction. Structured in person rehabilitation with a range of 14-36 visits over 2-9 months was generally not superior to structured home based rehabilitation with a range of 3-17 visits over 2-9 months for range of motion, quadriceps and hamstring muscle strength, knee laxity and functional outcomes in the short and long terms.

Knee Bracing:
Moderate certainty evidence exists from one review indicating postoperative knee bracing provides no benefit for knee laxity and physical function. There was low certainty evidence that bracing has no effect on self-reported function and pain.

Preoperative Rehabilitation:
There was low certainty evidence from one review that preoperative rehabilitation consisting of 3-6 weeks of strengthening and neuromuscular control exercises improves self-reported and physical function 3 months post ACL reconstruction for return to sport outcomes.

There is low certainty evidence from two reviews indicating that cryotherapy during the first 1-2 days post-surgery can reduce postoperative pain up to approximately 1-week post-surgery. Although cryotherapy didn’t increase any risk of adverse events, there is no evidence for its effect on outcomes beyond 1 week.

Psychological Interventions:
There is low certainty evidence from one review that showed psychological interventions consisting of guided imagery, relaxation, coping modelling and visual imagery for 6-12 weeks following surgery results in improvement in psychological and knee laxity outcomes.

Whole Body Vibration:
Two reviews found low to very-low certainty evidence that whole body vibration in addition to standard rehabilitation applied during multiple sessions over 10 weeks leads to a positive effect on quadriceps and hamstring strength, balance and physical function.

Supplement Use:
There is very low certainty evidence from one review suggesting that protein-based supplements taken between 6 and 18 months post operatively may help promote quadriceps size and strength.

Blood Flow Restriction Training:
There is very low certainty evidence from one review indicating blood flow restriction during low intensity resistance training in the first 2-16 weeks post-surgery results in greater improvements in muscle size and lean muscle mass compared with low intensity resistance training alone.

Neuromuscular Control Exercises:
Two reviews evaluating different neuromuscular control interventions such as balance, perturbation training, backward walking, and plyometrics compared with standard resistance based rehabilitation has low to very low certainty evidence indicating that two to three neuromuscular training sessions per week over 1-9 months is more effective than standard rehabilitation in order to improve quadriceps and hamstring strength and self-reported function.

Continuous Passive Motion:
There is very low certainty evidence from one review that indicated during the first week post-surgery, there is no more effective improvement of range of motion and pain from passive motion exercises compared to active motion exercises.

Clinical Application & Conclusions:

Overall, there is a low level of evidence regarding the effectiveness of rehabilitation interventions to improve symptomatic and functional outcomes in young adults with ACL injury with or without associated injuries. The strongest level of evidence (with moderate certainty) demonstrated that:
  • Neuromuscular electrical stimulation can improve quadriceps strength.
  • Open versus closed kinetic chain exercises are similarly effective for quadriceps strength, self-reported function and knee laxity.
  • Structured home-based rehabilitation is similarly effective compared to structured in-person rehabilitation for quadriceps and hamstring strength, self-reported function and knee laxity.
  • There is a lack of effectiveness for postoperative knee bracing on physical function and knee laxity.
The lack of systematic reviews evaluating isolated meniscal injury rehabilitation in young adults highlights a clear gap within the research. Systematic reviews mostly focused on older adults with degenerative meniscal lesions and were thus excluded from this current overview. Findings from these studies evaluating older adults suggest that an exercise therapy approach is an effective rehabilitation strategy, but given degenerative meniscal lesions are part of the OA disease process, the goals and expectation of rehabilitation are likely different than younger adults with traumatic injuries.

For young adults undergoing surgery, a goal-based exercise therapy program progressing through different phases of recovery over 9-12 months is considered the gold standard rehabilitation. Despite the perceived value of exercise, there is little certainty regarding its effectiveness and no clarity concerning specific therapeutic dosage and delivery. This stems from most trials failing to adequality document exercise frequency, intensity, volume and progression.

The findings of this review support recommendations in clinical practice guidelines but also provide important information that could be considered ‘contrary to popular belief’. For example, the belief of delaying open kinetic chain exercises until at least 4 weeks post-surgery did not match the results of this review, as early introduction of open chain exercises was not associated with any adverse outcomes, indicating that isolated quadriceps strengthening can be safely introduced early. The findings regarding bracing may also have surprised some clinicians. Overall, future research will help provide guidance to clinicians of what can be done in a safe manner and at what time point for these patients.

Study Methods:

A systematic literature search was done in June 2020 and June 2021 with no publication year or language restriction in MEDLINE, EMBASE, CINAHL, SPORTDiscus, and Cochrane Library. The search combined MeSH and text words related to ACL/meniscal injury, rehabilitation, and systematic review.

Systematic reviews of RCTs investigating non-surgical and non-pharmacological interventions in human participants following ACL and/or meniscal injury were eligible. For inclusion, reviews had to report on any outcome measurement related to pain, symptoms, function, reinjury, psychosocial factors, quality of life or adverse events. Physical measures such as knee range of motion, proprioception, and muscle strength were also included.

The exclusion criteria were non-English language, average age of participants greater than 30 years in studies following meniscal surgery in order to minimize the effects of pre-existing OA, and interventions following knee arthroplasty.

Two authors independently screened all titles, abstracts and full texts to determine eligibility.

The risk of bias was assessed using the Risk of Bias In Systematic Reviews tool. This tool uses signalling questions to identify concerns across four domains, including: 1) study eligibility criteria; 2) identification and selection of studies; 3) data collection and study appraisal; and 4) synthesis and findings. The overall risk of bias was determined through consensus. The authors also evaluated the quality of evidence pooled within the systematic reviews using a previously applied algorithm specifically developed to assign GRADE levels of evidence for overviews of systematic reviews.

Due to the heterogeneity of the original RCTs and lack of meta-analyses in the reviews, a best-evidence narrative synthesis was conducted rather than a quantitative analysis using a meta-analytical techniques. Systematic reviews with high risk of bias across all four domains were excluded.

In order to incorporate lived experiences, two individuals with lived experience of ACL injury and reconstruction and four clinicians contributed to the priority theme setting and outcomes for this review at an in-person meeting.

Study Strengths / Weaknesses:

  • This review provides a comprehensive assessment of the current state of the literature.
  • Overall, this review is high quality and methodologically strong.
  • The inclusion criteria were restricted to English language which could have excluded relevant non-English reviews.
  • There was a lack of ability to perform meta-analyses which limits the ability to comment on effect size. This speaks to the quality and heterogeneity of the literature rather than the quality of this review itself.
  • This review looked at other systematic reviews and therefore RCTs not included in those reviews may have been missed.

Additional References:

  1. Zbrojkiewicz D, Vertullo C, Grayson JE. Increasing rates of anterior cruciate ligament reconstruction in young Australians, 2000-2015. Med J Aust 2018; 208: 354–8.
  2. Starkey C. Injuries and illnesses in the National basketball association: a 10-year perspective. J Athl Train 2000; 35: 161–7.
  3. Smith TO, Postle K, Penny F, et al. Is reconstruction the best management strategy for anterior cruciate ligament rupture? A systematic review and meta-analysis comparing anterior cruciate ligament reconstruction versus non-operative treatment. Knee 2014; 21: 462–70.
  4. Webster KE, Feller JA. Exploring the high reinjury rate in younger patients undergoing anterior cruciate ligament reconstruction. Am J Sports Med 2016; 44: 2827–32.
  5. Filbay SR, Culvenor AG, Ackerman IN, et al. Quality of life in anterior cruciate ligament-deficient individuals: a systematic review and meta-analysis. Br J Sports Med 2015; 49: 1033–41.
  6. Culvenor AG, Lai CCH, Gabbe BJ, et al. Patellofemoral osteoarthritis is prevalent and associated with worse symptoms and function after hamstring tendon autograft ACL reconstruction. Br J Sports Med 2014; 48: 435–9.
  7. Culvenor AG, Cook JL, Collins NJ, et al. Is patellofemoral joint osteoarthritis an under-recognised outcome of anterior cruciate ligament reconstruction? A narrative literature review. Br J Sports Med 2013; 47: 66–70.
  8. Poulsen E, Goncalves GH, Bricca A, et al. Knee osteoarthritis risk is increased 4-6 fold after knee injury - a systematic review and meta-analysis. Br J Sports Med 2019; 53: 1454–63.
  9. Andrade R, Pereira R, van Cingel R, et al. How should clinicians rehabilitate patients after ACL reconstruction? A systematic review of clinical practice guidelines (CpGs) with a focus on quality appraisal (agree II). Br J Sports Med 2020; 54: 512–9.
  10. Thrush C, Porter TJ, Devitt BM. No evidence for the most appropriate postoperative rehabilitation protocol following anterior cruciate ligament reconstruction with concomitant articular cartilage lesions: a systematic review. Knee Surg Sports Traumatol Arthrosc 2018; 26: 1065–73.

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