Postoperative rehabilitation of the anterior cruciate ligament (ACL) 2026 update

A clinical review based on the most recent meta-analyses and international consensus statements: Aspetar 2023, Panther Symposium 2021, Piussi 2024, Paterno 2022, Gopinatth 2025, Li 2025, van Melick 2025.

What are the fundamentals to know about post-ACL rehabilitation?🔗 Copy

How is this injury defined, who is affected and what are the risk factors?

Rupture of the anterior cruciate ligament (ACL) is one of the most common and most disabling knee ligament injuries, particularly in young, active people.¹ It most often occurs without direct contact, during deceleration, changes of direction or a poorly controlled landing.² The sports most at risk are football, basketball, handball and alpine skiing.

The meta-analysis by Montalvo et al. 2019 (8 prospective studies, BJSM)¹ establishes that the risk of ACL rupture in women is on average 1.7 times higher than in men in the same sports (IRR 1.7; 95% CI 1.4-2.2). The relative risk can reach 2 to 3 in women's pivoting sports (basketball, football, handball).

The risk factors are multifactorial and fall into two categories:

• Intrinsic :
  • Anatomical : narrow intercondylar notch, increased posterior tibial slope, wider Q angle.
  • Hormonal : oestrogen fluctuations that may modulate ligament laxity (weak evidence).
  • Neuromuscular : quadriceps/hamstring dominance, dynamic knee valgus on landing, deficient trunk control, modifiable factors through preventive training.¹²
• Extrinsic : type of footwear, playing surface, weather conditions.

In young athletes (<25 years) returning to pivoting or contact sports, the Wiggins 2016 meta-analysis documents a cumulative incidence of 23% second ACL injury (same side or opposite side).¹³ The Piussi 2024 meta-analysis (21 recent studies) updates that figure to a pooled incidence of 16.9% (CI 12.8-21.6%).¹⁴

What happens in the body and how does the graft evolve?

After reconstruction, the graft (autograft, patellar tendon or hamstrings, or allograft) does not immediately become a functional ligament. It undergoes a long biological process called « ligamentisation ».

The landmark histological work of Claes et al. 2011 (AJSM, systematic review)² showed that the graft never entirely reproduces the histological and biomechanical properties of the native ACL. The process runs in three phases:

1. Avascular necrosis (0-4 weeks) : massive cell loss in the graft, which becomes an unvascularised collagen scaffold.
2. Revascularisation (4-12 weeks) : invasion by fibroblasts and neovascularisation. Point of maximum mechanical weakness.
3. Remodelling (3 months to 4 years) : progressive maturation of the collagen. The structure never regains its native organisation. Biomechanical maturation continues until 24-48 months (and beyond in some patients).

Beyond this local biology, the rupture and the surgery induce lasting neurocognitive disturbances . The loss of ligament mechanoreceptors leads to deafferentation and central reorganisation of motor control, documented on functional imaging.¹⁵ As a result, the following are commonly seen after surgery:

• Marked atrophy and persistent quadriceps weakness, partly through arthrogenic muscle inhibition.¹⁶
• Some biomechanical asymmetries persisting to 9-12 months after surgery and beyond (King 2018).
• A degree of kinesiophobia that can hinder progress and return to sport (Trigsted 2018).¹⁰

How can progress after ACL reconstruction be assessed with certainty?🔗 Copy

Assessment after ACL reconstruction must go well beyond the postoperative calendar. The modern approach, supported by the Aspetar 2023consensus¹ and the Delaware-Oslo cohort,² is multidimensional and based on objective criteria combined with listening to the patient.

What questions should be asked to understand the patient?

The history puts the objective test results in context and identifies the barriers to successful rehabilitation.

• Goals and target level : pivoting sport? Competition? Recreational? The level of risk determines how strict the validation criteria should be.
• Pain, swelling, effusions, locking : a recurrent effusion or locking should raise suspicion of an additional intra-articular problem.
• Psychological dimension : kinesiophobia is a major predictor of successful RTS.³ Use the ACL-RSI (Anterior Cruciate Ligament-Return to Sport after Injury)⁴ scale systematically: a score <65/100 predicts an increased risk of second injury; the <76.7 threshold has 90% sensitivity for risk in those aged ≤20.³
• Adherence to the programme and the difficulties encountered: a patient who drops out is a patient at risk.

Which clinical tests should be carried out and which differential diagnoses must be ruled out?

Ligament stability : the Lachman test remains the most sensitive clinical test for assessing the integrity of the ACL graft (Sn 81%, Sp 85% without anaesthesia; Sn 91% under anaesthesia, van Eck 2013 meta-analysis).⁵ The pivot shift is highly specific but hard to perform on an awake, apprehensive patient.

Muscle strength : isokinetic dynamometry is the reference standard. The consensus target is a Limb Symmetry Index (LSI) >90% for the quadriceps and the hamstrings.

Functional tests : a battery of hop tests, single hop for distance, triple hop, crossover hop, 6-metre timed hop. An LSI >90% is required for each.

Limits of the functional tests : Webster & Hewett (2019, SR/MA)⁷ concluded that there is no solid evidence that the current batteries significantly reduce the risk of re-rupture. Davies et al. 2020 judged the hop tests « equivocal » in predictive value.⁸

Should patients be stratified, and for what benefit?

Yes. Early stratification makes it possible to target interventions at the at-risk profiles rather than applying a « one size fits all » protocol. The landmark study Toole et al. 2017 (JOSPT, n=156 young athletes) showed that only 13.9% of young people met all the combined criteria at the time they were cleared for RTS: 27.8% for quadriceps strength alone, 53% for the hop tests alone.¹⁰

Early stratification on the ACL-RSI score at 3 and 6 months, the quadriceps strength deficit at 3 months and movement quality (2D analysis of dynamic valgus in a drop jump) makes it possible to steer treatment towards the patient's real deficits.¹¹

Which treatment strategies are the most effective?🔗 Copy

The recommendations of the Aspetar 2023 guideline,¹ of the Panther Symposium 2021consensus² and of the van Melick 2025editorial³ converge: rehabilitation must be criteria-based (and not driven by the calendar alone) and combine several complementary modalities.

Where do you start? What hierarchy of interventions?

The immediate postoperative phase lays the foundations of success. The priorities are regaining range, controlling swelling and neuromuscular activation.

• Regaining full extension : this is the absolute priority of the first 2 weeks. A deficit of ≥5° is associated with gait disturbance, persistent quadriceps weakness and an increased risk of patellofemoral and tibiofemoral osteoarthritis.⁴
• Early weight-bearing with aids as tolerated: safe and beneficial for function (Aspetar 2023).¹
• Early neuromuscular activation of the quadriceps (isometrics, sets) to counter arthrogenic inhibition.⁵
• Cryotherapy + compression in the first few days to manage swelling and pain.

What is the place of exercise, and the optimal combination?

Therapeutic exercise is the cornerstone of rehabilitation. The historical debate about open versus closed chain is settled today.

The meta-analysis by Pamboris et al. 2024 (Front Sports Act Living)⁶ confirms:

• The open kinetic chain (OKC), leg extension within a protected range of 90°→40°, is superior for isokinetic quadriceps strength gains (MD +28.1 Nm at 12 weeks).
• The closed kinetic chain (CKC) is better for early pain.
• No difference in joint laxity where the open chain is introduced progressively (from week 4-6 onwards).

The reference approach is therefore the combination of OKC + CKC, with progression in range and in load.

Manual therapies, NMES, BFR: how effective are they really?

Several adjunct modalities can speed up strength gains, particularly in the early phase.

How do you educate the patient and address the psychological dimension?

Physical recovery alone is not enough. Psychological factors weigh as heavily as strength.

The meta-analysis by Ardern et al. 2014 (BJSM, n=7,556 patients)⁷ shows that despite good physical recovery:

The gap between 81% and 55% is mainly psychological. The levers available:

• Therapeutic education : the stages of healing, the logic behind the exercises, managing expectations.
• SMART goals (Specific, Measurable, Achievable, Realistic, Time-bound).
• ACL-RSI assessment at regular intervals (3, 6, 9 months).
• Graded exposure to anxiety-provoking sporting situations.
• Referral to a sport psychologist where kinesiophobia persists (ACL-RSI score <65 at 6 months).

How do you plan a safe, lasting return to sport?🔗 Copy

Return to sport (RTS) is a process, not an event. It combines three pillars, all of them necessary : a minimum biological delay, a battery of functional criteria, and psychological readiness. No pillar is enough on its own.

How do you make the patient an active participant in their recovery?

Self-management rests on three pillars:

1. Therapeutic education : understanding the injury, the stages of healing, the logic behind the exercises.
2. Setting SMART goals and patient/therapist collaboration.
3. Psychological support and strengthening self-efficacy through progressive successes.¹

When and how should a safe return to sport be planned?

The RTS decision combines three cumulative :

1. A minimum biological delay of 9 months. The Beischer 2020 cohort² and the Piussi 2024 meta-analysis³ converge: returning before 9 months multiplies the risk of a further rupture by 7 (HR 7.0; CI 1.6-31.5). The pooled incidence of second ACL rupture in the recent literature is 16.9% (CI 12.8-21.6%).

2. Objective functional criteria. The landmark study Kyritsis et al. 2016 (BJSM, n=158)⁴ established 6 criteria, failure of which multiplies the risk of re-rupture by 4 (HR 4.1; CI 1.9-9.2):

• Isokinetic quadriceps and hamstrings at 60°/s, 180°/s, 300°/s: LSI >90%
• Running T-test (agility)
• Single hop test: LSI >90%
• Triple crossover hop: LSI >90%

3. Psychological readiness. The ACL-RSI scale⁵ makes it possible to quantify the patient's confidence and their fear of re-injury. Main thresholds:

• Score <56 at 4 months: predicts non-return to sport at 12 months
• Score <65 at 6 months: predicts a low probability of RTS to pivoting or contact sport
• Score <76.7 in those aged ≤20: 90% sensitivity for the risk of second injury⁶

What do the published clinical cases teach us?🔗 Copy

The case reports published on PubMed/PMC illustrate how the evidence-based principles translate into concrete situations.

Case 1: A professional footballer after 3 ipsilateral reconstructions (Noronha 2020)

A 32-year-old professional footballer who had sustained three successive ACL ruptures on the same side (hamstring graft, then patellar tendon, then Achilles tendon allograft).¹ The patient progressively resumed full training at 8 months and competition at the highest level at 9 months after the 3rd operation. At 36 months of follow-up: no pain, no instability, professional level maintained.

Clinical lesson: even after repeated failures, a structured protocol + a suitable graft + objective criteria allow a return to the top level. Clinical resilience does exist.

Case 2: Cyclops syndrome diagnosed late (Singh 2021)

A 26-year-old patient with persistent loss of extension 1 year after reconstruction.² The clinical picture suggests cyclops syndrome; MRI confirms an anterior intercondylar fibrous nodule mechanically blocking extension. Conservative rehabilitation (intensive joint mobilisation, stretching) having failed, the patient undergoes arthroscopic release with excision. Full recovery of extension at 3 months after the second-look procedure.

Clinical lesson: a loss of extension that does not recover is a red flag: refer promptly to the surgeon. The « patient who plateaus » deserves a follow-up MRI.

Case 3: Multi-ligament reconstruction ACL + PCL + meniscal roots (Adi 2025)

A 19-year-old patient with a complete ACL + PCL rupture and tears of the posterior roots of both menisci.³ Simultaneous reconstruction (peroneus longus for the PCL, hamstrings for the ACL) + arthroscopic repair of the roots. At 9 months after surgery: ROM 0-140°, bi-ligamentous stability restored, no significant difference in thigh circumference compared with the uninjured side.

Clinical lesson: multi-ligament cases are biomechanically demanding (grafts under opposing constraints). The protective phases are longer and weight-bearing more cautious. Return to sport is rarely before 12-15 months.

Other notable examples:

• Joreitz 2020 (IJSPT, case series n=19): a 5-phase criterion-based protocol, 84% return to pre-injury level at 2 years, a single re-injury among 19 who completed: proof of feasibility.⁴
• Meierbachtol 2020 (OJSM, n=33 patients aged 14-30): a 5-week group RTS programme with graded exposure therapy: fear of pivoting is the most common; every fear decreases significantly after the programme; the ACL-RSI proves more discriminating than the TSK-11.⁵

How can these recommendations be applied in practice?🔗 Copy

Clinical application rests on two skills that are often under-invested in: knowing when to refer and knowing how to measure your own results.

When, and to which professionals, should you refer?

Yellow flags (psychosocial): referral to a psychologist / CBT: persistent kinesiophobia, catastrophising, mistaken beliefs about pain, depressive symptoms.¹

Interprofessional collaboration : sports physician, orthopaedic surgeon, podiatrist (foot posture), nutritionist (body composition), sport psychologist. Multidisciplinary biopsychosocial management improves outcomes in chronic conditions.²

How do you measure outcomes and overcome the barriers to implementation?

Systematic use of PROMs (Patient-Reported Outcome Measures) is recommended.³ For the ACL:

• KOOS (Knee Injury and Osteoarthritis Outcome Score): function and quality of life
• IKDC (International Knee Documentation Committee): overall subjective score
• ACL-RSI: psychological readiness
• Tegner and Marx: level of sporting activity
• PSFS (Patient-Specific Functional Scale): personalised goals

The documented barriers to implementation (Scurlock-Evans 2014, SR in allied health)⁴:

• Lack of time in the consultation → integrated digital PROM tools
• Difficulty reading the literature → continuing education, podcasts (BJSM, JOSPT), CATs (critically appraised topics)
• Beliefs and habits → audit + feedback, peer mentoring
• A funding system that pays for volume, not quality: a structural fix