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Optimising the early‐stage rehabilitation process post‐ACL Reconstruction

Review written by Dr Teddy Willsey info

Key Points

  1. Range of motion deficits seen in early post-ACLR can predict suboptimal outcomes at later stages of rehabilitation.
  2. The persistent loss of quadriceps strength and muscle activation represents a significant challenge during ACLR.
  3. Preserving physical fitness during the early stage of post-ACLR is strongly recommended.


Outcomes following ACL reconstruction (ACLR) need improving. While short- and medium-term patient reported outcomes following ACLR tend to be consistent with most major surgeries, long-term outcomes are significantly worse. Only 80% of recreational athletes return to sport (RTS), with only 65% returning to their pre-injury level (1). And while elite athletes RTS at higher levels, they experience long term decreases in performance and a reduced career length.Moreover, nearly one third of athletes who do choose to RTS will experience a second injury within 2 years (2).

The authors of this paper sought to provide practitioners with a thorough manuscript on how to optimize the early-stage rehabilitation process post-ACLR.

Only 80% of recreational athletes return to sport, with only 65% returning to their pre-injury level.
Clinicians should work to help athletes find safe and engaging ways to preserve their fitness and work around their injury as early as possible.


The multi-disciplinary author team includes a physiotherapist, sports medicine physician, surgeon, rehabilitation specialist, sports scientist and strength and conditioning specialist, sport psychologist, and sport and exercise physiologist, all with specific experience and expertise in working with ACLR.

The authors highlight six main dimensions during the early stage: 1) pain and swelling, 2) knee joint range of motion, 3) arthrogenic muscle inhibition (AMI) and muscle strength, 4) movement quality and neuromuscular control during ADLs, 5) psycho-social-cultural and environmental factors, and 6) physical fitness preservation.


This paper is a review article and includes expert opinion and numerous anecdotes. Although it does not represent a high level of evidence from a research rigor viewpoint, it is a helpful and appreciated contribution to the body of knowledge on ACLR rehabilitation.


Pre-operative It would be remiss to discuss the early post-operative period without mentioning the strong correlation with the preoperative status of the knee and short- and medium-term outcomes.

Patients with full knee extension, minimal swelling, and no knee extension lag preoperatively have better post-surgical outcomes, regain their ROM faster, and demonstrate better quadriceps strength with decreased AMI. A criterion based preoperative rehabilitation program is recommended to work toward the aforementioned goals.

Pain and swelling Pain and swelling create a catabolic joint environment and affect joint proprioception contributing to AMI. Swelling is associated with irritation of intra-articular structures and articular disorders. The use of cryotherapy, compression, and elevation are recommended. Active ROM exercises and active isotonic exercises may be initiated early to increase venous blood return and reduce swelling. Excessive swelling should be managed with anti-inflammatory drugs and intra-articular aspiration.

Swelling should be monitored and documented regularly as it can change daily. A maximum pain rating of 4/10 is recommended during rehabilitation. The pain scale should be anchored early on and applied to specific tasks to improve communication and assist in monitoring pain over time.

Knee joint range of motion Full knee extension is essential to safely progress the patient off their crutches post-ACLR. Sufficient knee flexion (110-120°) should be achieved by 4-6 weeks, with this ROM required for patients to begin stationary cycling. ROM exercises should generally begin immediately post-ACLR. Early motion is beneficial for avoiding capsular contractions and reducing pain and swelling. Anterior knee pain incidence and the risk of cyclops lesion can be reduced through early stimulation of knee hyperextension.

AMI, muscle activation and strength Residual deficits in knee extensor muscle size and strength post-ACLR are associated with reduced knee function, alterations in biomechanics, increased patellofemoral joint (PFJ) contact pressure, and increased second injury risk. It is recommended to begin testing quadriceps strength at 6 weeks post-op when possible. Strength at 6-weeks post-ACLR has been shown to predict performance 6-months post-ACLR (3).

AMI is the phenomenon where uninjured muscle becomes reflexively inhibited because of the injury to the joint it is associated with. The process is thought to be particularly impactful following ACL reconstruction due to the loss of mechanoreceptors from the large intra-articular ligament. Quadriceps AMI leads to an inability to recruit high-threshold motor units. In order to optimize quadriceps activation, resistance training during the early stage can be performed utilizing evidence based supplementary techniques: pre-exercise focal joint cooling, TENS, pre-fatiguing of the hamstrings, NMES, BFR, and cross-education.

Full ROM open kinetic chain (OKC) knee extension is safe and recommended at lighter loads. As loads increase, it is recommended to reduce ROM to 90-45 deg of knee flexion, however this is more due to knee comfort rather than a concern of stress on the ACL graft. OKC exercise helps to isolate the quadriceps. Closed kinetic chain (CKC)exercise is recommended for general strengthand function, however it is less effective for quadriceps strengthening in the early stage due to movement compensation and tissue tolerance.

Higher volume and lower intensity loading schemes ae recommended. Isometric knee extension isrecommended up to 5x45 seconds, 1-2 times per day. Heavy slow resistance training is recommended for OKC knee extension with 15-25 RM loads, increasing in intensity from 4-12 weeks, working at a 3 sec concentric and 3 sec eccentric tempo (4). Performing a working set close to volitional fatigue facilitates more complete activation of the motor unit pool, thereby facilitating activation of higher threshold type II motor units which would not otherwise be activated due to AMI and low load tolerance.

It is not recommended to delay strengthening of the hamstrings following a hamstring graft. There is no evidence to suggest early isometrics and light strengthening is contraindicated.

Movement quality and neuromuscular control during ADLs Normal gait and movement patterns should be restored as early as possible. Aberrant knee moments during gait at four weeks are significantly related to knee moments during running at four months. Limb loading asymmetries found at one month are independent predictors of limb asymmetries in the vertical jump at the time of RTS.

Disruption to the native ACL alters somatosensory activity. The resultant decrease in joint position sense and kinesthesia, along with nociceptor activity associated with pain and swelling, may potentially impair movement quality. It is essential to incorporate sensorimotor and neurocognitive factors, and to initiate these early post-ACLR with gait retraining and “easy” exercise.

Psycho-social-cultural and environmental factors Clinicians can assist athletes in the challenges they experience comprehending and understanding the meaning of their ACL injury, coping with their loss of sport and physical mobility, and working through common emotional reactions of shock, anger, fear, anxiety, depression, sense of loss, helplessness, frustration, and psychological and existential pain.

Cultural norms tend to encourage athletes to suppress negative injury-related emotions and do not always provide pathways for injured athletes to receive the support they need. It is important for the clinician and support providers to understand the person and all the dimensions of their life that the injury has an impact on. Effective communication and a strong patient-therapist alliance have been shown to improve outcomes.

Physical fitness preservation Key elements of early-stage re-conditioning are a minimal effective dose approach cardiovascular fitness and preventing atrophy. Clinicians can assist by offering strength training options for the contralateral uninjured side, the joints adjacent to the injured knee, and the trunk and upper body.

Loss of cardiovascular fitness post-ACLR leads to lower baseline fitness levels as an athlete enters mid- and late-stage rehabilitation. Lower fatigue resistance during early RTS can lead to greater second injury risk. The CV fitness an elite athlete demonstrates can take months to rebuild.


Buckthorpe M, Gokeler A, Herrington L, HughesM, Grassi A, Wadey R, Patterson S, Compagnin A, La Rosa G, Della VillaF (2023)Optimising the Early-Stage Rehabilitation Process Post-ACL Reconstruction. Sports medicine, published online first.


  1. Arundale AJH, Silvers-Granelli HJ, Snyder-Mackler L. Career length and injury incidence after anterior cruciate ligament reconstruction in major league soccer players. (2018). Orthop J Sports Med.
  2. Lai CCH, Feller JA, Webster KE. Fifteen-year audit of anterior cruciate ligament reconstructions in the Australian Football League from 1999 to 2013: return to play and subsequent ACL injury. (2018). Am J Sports Med.
  3. Pua YH, Mentiplay BF, Clark RA, Ho JY. Associations among quadriceps strength and rate of torque development 6 weeks post anterior cruciate ligament reconstruction and future hop and ver- tical jump performance: a prospective cohort study. (2017). J Orthop Sports Phys Ther.
  4. Welling W, Benjaminse A, Lemmink K, Dingenen B, Gokeler A. Progressive strength training restores quadriceps and hamstring muscle strength within 7 months after ACL reconstruction in amateur male soccer players. (2019). Phys Ther Sport.
Optimising the early‐stage rehabilitation… By Dr Teddy Willsey