Anterior cruciate ligament reconstructions (ACLR) are among the most common sports medicine procedure performed in the United States. It is estimated that over 200,000 ACL injuries occur each year, with at least half electing to undergo surgical intervention.
While we know the number of ACLRs has continued to climb, even the most recent data may be an inaccurate representation, as most of these numbers are based on expert opinion and insurance company databases.1-4
Even though it is a common injury, approving an athlete to return to sport after ACLR is not as easy as it seems. For example, Ardern et al. found that only 55% of patients after an ACLR had returned to their premorbid activity level at a mean 39.6 months following surgery.5
Similarly, in a different study, Ardern et al. demonstrated that only 82% of patients who underwear ACLR were able to return to sports activity.6
The percentages were even lower when considering those who returned to premorbid participation level (63%) and those who returned to playing competitive sports (44%), even though about 90% of patients presented with normal or nearly normal knee function.7
Similarly, returning to cutting and pivoting sports increases an athlete’s odds for an ipsilateral (same side) second ACL injury by 3.9 times and for a contralateral (opposite side) injury by 5 times.8
In addition, risk of re-injury is increased in the short term if you are younger and increased ipsilaterally if you are male and contralaterally if you are female.
Regardless of your gender, if you get your ACL reconstructed, you are at higher risk for osteoarthritis in the long-term.9
What is the criteria for returning to sports after an ACL surgery?
Despite significant advances in ACL injury diagnosis, surgical techniques, and rehabilitation over the last 40 years, substantial challenges still exist for specific return-to-sport criteria at a pre-injury level per continued high rates of graph failure, re-injury, and quadriceps and hamstring weakness post-surgery.
There is a plethora of ACL recovery timelines for athletes with many different conflicting views on the appropriate method of rehabilitation.
Because of this, it is safe to assume that there is no “one all be all” ACL protocol or recovery timeline that is going to apply to all athletes who have undergone reconstruction.
In general, clinicians should avoid using strict time frames when treating patients following ACL reconstruction.
Rehabilitation specialists should be able to progress the patient as improvements in strength, edema, proprioception, pain, and range of motion are demonstrated.
Prior to returning to sport, specific return to sport testing should be conducted with passing scores (this will be discussed in the next article so stay tuned!). Time from surgery should be one of the last considerations, and really should only be used to determine it is too soon to start an activity.4
Pre-operatively, one would like to see full knee extension ROM, absent or minimal effusion, and no quad lag with a straight leg raise.4,10
Post-operatively, there are no weight-bearing restrictions unless you have a concomitant injury; in contrast, immediate weight-bearing is encouraged to enhance quadriceps function and knee extension ROM and can be initiated without forgoing graft integrity.11
However, depending on the surgeon, if you had a meniscal repair, you will generally have restricted knee range of motion and limited weight-bearing for the first 4-6 weeks. Depending on where the graft for the new ACL is taken from during a reconstruction, there may be restrictions as well.
Grafts taken from the patellar tendon typically do not have any restrictions but be aware that it is highly likely that patellofemoral (front of the knee) irritation and pain is imminent.
Grafts from the hamstring tendon (semitendinosus) will limit prohibit resisted hamstring exercises for about 12 weeks post-operatively.10
Another technique that is gaining popularity is ACL repairs, in which the native and damaged ACL is sutured together.
The ability to perform this type of ACL surgery is dependent on where the ligament in injured; because you have to wait for the repaired ligament to heal, the initial weight-bearing restrictions are more stringent.13
The outline below is only an EXAMPLE of an ACL recovery timeline for athletes. It is important to note that there is no consensus on ACLR post-operative protocols, but this particular protocol is based out of the University of Delaware and is currently being utilized as the most current evidence for ACL reconstruction.
Several other protocols and my personal experienced have influenced this particular ACL recovery timeline. Nothing written here is meant to replace your clinical judgment.4,10,13
Immediate Post-operative (Week 1)
Since the last set of guidelines were published in 1996, surgical techniques have improved and fixation techniques are strong enough to withstand early mobilization and weight-bearing, providing no concomitant injuries are present.
- Active and passive knee ROM equal 0° to 90° with full terminal knee extension as soon as possible13
- Active quadriceps contraction
Loss of knee extension ROM is a common issue following ACLR, with Mauro et al. demonstrating that 23.3% of patients have more than a 5° difference side-to-side in passive knee extension ROM 4 weeks after ACLR.14 Even small losses of knee extension can result in less than optimal results following ACLR, with the biggest problem being weaker quadriceps.15-18
If full extension (considered within 5° of the uninvolved knee) is not achieved by 2 weeks post-operatively, low-load long-duration stretching, like prone or bag hangs, should be utilized to restore full knee extension.19-20
Decreased quadriceps strength after ACL reconstruction has been reported to be present months to years following surgery.17
Neuromuscular electrical stimulation (NMES) should be used as an adjunct to a good quadriceps strengthening program and has been shown to improve outcomes.21-23
After ACLR, the quads are often inhibited, which limits a patient’s ability to voluntarily contract them after surgery. NMES directly recruits the motor neurons affected by the inhibition, which increases quad strength post-operatively better than exercise alone.24-26
- Table slides/wall slides
- Gastroc stretch with strap
- Patellar mobilizations
- Gait training (with 1-2 crutches)
- Stationary bike for ROM
- Quad sets
- LAQs (90-45°)
- Hip 4-way
Early Post-operative (Week 2)
- Full passive knee extension and walking with terminal knee extension
- Knee flexion >110°
- Walking without crutches
- Walking step over
- Step up the stairs
- Use of bike/stair climber
Patients will begin weight-bearing (closed-kinetic chain) exercises in this phase, including step-ups and wall sits/squats in a pain-free range (usually 0°-60°), which have been shown to be safe and effective.27-28
There is, however, still some debate over the use of non-weight-bearing exercises when it comes to post-op ACLR rehab. Mikkelson et al. found increased quadriceps strength and return to sport rate but no difference in graft laxity with a rehab program with both open and closed-kinetic chain exercises compared to just closed-kinetic chain alone.29
Because of this, it is appropriate to perform both non-weight-bearing and weight-bearing exercises into a rehab program without negative effects on the healing ACL graft.
However, by limiting knee ROM from 90° to 45° for non-weight-bearing exercises for the first 12 weeks post-op, undue strain on the graft can be avoided while gaining all the benefits from open-kinetic chain exercises.
- Step ups
- Wall sits/squats
- Leg press/shuttle
Intermediate Post-operative (Weeks 3-5)
- Knee flexion to within 10° of uninvolved side
- Quad strength >60% of uninvolved
Balance and proprioceptive training begins in this phase in order to address any muscle inhibition or impaired sensorimotor function related to the recent surgery
Perturbation training, initially described by Fitzgerald et al.30 in patients who elect to forgo ACL surgery, may be used to maximize functional outcomes in athletes post-op ACLR.31
- Single leg balance (eyes closed, unstable surface to increase difficulty, throwing a ball)
- Single leg cone taps to mat, floor
- Squats/squat holds on a tilt board
Late Post-operative (Weeks 6-8)
- Quad strength <80%
- Normal gait
- Full ROM
- No or minimal effusion
The autograft during this phase is reaching its weakest point structurally postoperatively, which is unfortunately around the time that patients are finally starting to feel relatively normal.32
In this phase, therapeutic exercise and neuromuscular re-education will be increased in intensity and duration.
Transitional (Weeks 9-12)
- Maintaining quad strength
- Running progression can be initiation once patient can complete a single leg squat without compensations and appropriately land a hop down with involved leg in addition to meeting to goals of the late post-operative phase.
This phase is where I start to differ from the protocol discussed above. While some patients may meet the criteria for return to running faster than 12 weeks, I don’t generally allow my athletes to return prior to this.
Most of the time, we are dealing with an extension deficit and/or a quad strength deficit. If they don’t have the quad strength to complete one proper single leg squat, I am not going to make them do it repeatedly on a treadmill.
Return to Sport (12 weeks +)
Currently, there is little agreement as to when it is safe to return to sports participation. Several forms of return-to-sports assessments, which will be discussed in a future article, often dictate return to play. These need to be passed in order to return to full athletic activities.
Furthermore recent biomechanical data has shown that altered neuromuscular control of the hip and knee as well as postural stability deficits after ACL reconstruction are predictors of a second ACL injury after an athlete has returned to sport.
Studies have demonstrated decreased muscular strength, joint position sense, and postural stability for 6 months to 2 years following reconstruction.13,33-37
Patients are going to continue to get their ACLs reconstructed, which means that the sports medicine team needs to have some idea of an ACL recovery timeline for athletes.
However, likely risk of future or secondary re-injury and a high likelihood of osteoarthritis in the future may help us consider our options for our future knee health. Maybe the question isn’t ‘when can we return to sport,’ but ‘should we?’