ACL Rehabilitation: Re-injury and Return to Sport Tests


ACL Re-injury

Despite advancement in surgical procedures, the outcomes following ACL-reconstruction continue to be poor. Less than 50% of athletes are able to regain their pre-injury level of performance[1]. For those who returned successfully to sport, re-injury remains a risk factor.

The incidence of re-injury in the first two years following reconstruction is estimated to be 6 times greater than those who didn't suffer ACL injury. This incidence is much higher in female athletes[2]. A study reported 29.5% ACL re-injury in the second year with 20% sustaining contralateral injury[2]. The risk of re-injury extends up to 5 years following injury[3].

Re-injury Risk Factors

Risk factors of primary and second ACL injuries have been investigated widely in the literature. Biomechanical factors such as abnormal loading distribution patters around the knee, increased external knee abduction moment in females[4], side-to-side differences in lower extremities, frontal-plane displacement of the trunk[5] and reduced lower extremity flexor activation in vertical jump[4] have been associated with ACL injury.

Deficits in Quadriceps weakness is a common persisting issue after surgery[6] which is manifested through abnormal loading patterns in gait and sports activities.A deficit of about 20% of quadriceps strength compared to the opposite side is found in athletes after ACL reconstruction. However, even a 90% quadriceps index is not necessarily associated with normal neuromuscular control.

Four neuromuscular control deficits were considered to be risk factors for second ACL injury[4]:

  • Hip rotational control deficits
  • Excessive frontal-plane knee mechanics
  • Knee flexor deficits
  • Postural control deficits

Asymmetry in the kinematics and differences in moment arm between involved side joints compared to the other side is another factor that continues to manifest years following surgery[7].

Abnormal movement patterns are often present bilaterally. changes in kinetics and kinematics of both knees. Studies report higher peak knee angles, moments, and joint powers relative to controls[6]. 3-dimensional biomechanical analyses and postural stability testing reported hip rotation moment changes during landing in the uninvolved side, frontal-plane knee motion during landing, sagittal plane knee moment asymmetries at initial contact, and deficits in postural stability on the reconstructed limb[8].

The development of compensatory strategies of the uninvolved hip is considered to be the primary predictor of risk in athletes who sustained a second ACL injury within the first year of return to play[8]. Therefore, engaging both limbs in rehabilitation is a necessity[6].

Gender may be a contributing factor to secondary ACL injury. Graft rupture is more likely to occur in men, according to a 15-year cohort[9]. Another study reported no difference between sexes in graft rupture, however, contralateral injury was higher in female athletes[10].

Young athletes are at a higher risk of re-injury and also to contralateral injury [6].

Prevention of Re-injury

Re-injury and the need to undergo a second ACL-reconstruction place the knee joint under devastating complications of developing OA, knee instability and difficulty in returning to sport. About 25% of athletes undergo a second revision within 6 years of the primary ACL revision[11].

Understanding risk factors associated with re-injury is important to target all deficits in the rehabilitation program.

Side-to-side Quadriceps symmetry is essential to return to sport and prevention of future re-injury. Hamstrings/Quadriceps strength ratio is another important factor to be considered in rehabilitation. The aim is to achieve at least 85% strength symmetry before returning to sport[6].

Single-leg plyometric tests can give the clinician an overview on how the injured limb is functioning and the differences between both sides. Findings in these tests should be considered when setting up the rehabilitation plan[6].

A study reported 38.2% re-injuries in athletes who failed return to sport criteria suffered versus 5.6% of those who passed. The same study estimates 84% reduction of knee re-injury rates in patients who passes return to sport criteria[12].

Does timing play a role in preventing re-Injury?

A study reported a significant reduction by 51% for each month return to sport was delayed until 9 months after surgery, after which no further risk reduction was observed. Delaying return to sport to 9 months gives sufficient time to recondition the athlete and train them on all sport-specific drills necessary to avoid instability and future re-injury[12].

The Influence of Psychological factors

Pain-related fear plays a key role in distinguishing athletes who may not be able to return to pre-injury levels. Lack of confidence and fear pf re-injury are believed to influence function. For these reasons, assessment of these factors must be included in the management plan[13].

Fear avoidance model, self-efficacy theory, stress, social support, and athletic self-identity explain inability to return to sport in athletes with full level of function and are predictive of outcomes after surgery[14].

Motivation also plays a role when engaging an athlete into the rehabilitation plan (45% of community-level athletes discontinuing supervised rehabilitation by 3 months post ACL-reconstruction[12]) and also to go through all stages of return to sport rehab. An athlete may feel ready and competitive before passing all stages and may discourage rehabilitation before regaining all required criteria to return to sport. Quality patient education, goal setting, frequent feedback and individualization of the rehabilitation plan are all recommended to stimulate motivation[15].

Predicting Functional Outcomes after Surgery

Factors such as Age, gender, body mass index (BMI), smoking, concomitant injuries, and physical impairments before and after surgery have an influence on the expected outcomes after surgery. However, they don't explain variance in knee function after ACL reconstruction and rehabilitation

Logerstedt et al[16] reported that conducting the 4 hop tests 6 months after surgery is statistically significant with predicted self-reported knee function. Out of the 4 tests, the 6-m timed hop and the crossover hop tests were the best predictors. The 6-m timed hop predisposes the knee in neuromuscular control challenge and highlights asymmetries.

Conducting these tests 6 months after surgery at the time before return to sport specific training gives sufficient time to address deficits that may contribute to re-injury.

The following factors, if present, can predict return to pre-injury status[17]:

  • Less knee effusion
  • Fewer episodes of knee giving way
  • Lower knee pain intensity
  • Higher quadriceps peak torque-body weight ratio
  • Higher score on the International Knee Documentation Committee Subjective Knee Evaluation Form
  • Lower levels of kinesiophobia

Return to Sport

With the high incidence of re-injury and the evidence of poor outcomes of ACL-reconstruction revision, a need for a return to sport protocol has developed.

Myer et al [18] proposed four stages of advanced rehabilitation protocol to address common deficits found in athletes after ACL-reconstruction:

Stage 1: Dynamic stabilization and core strengthening

Stage 2: Functional strengthening

Stage 3: Power development

Stage 4: Sports performance symmetry.

The aim of this protocol is to recondition athletes to function optimally by targeting neuromuscular deficits to minimize rates of re-injury.

Monitoring signs of overload in all stages is critical to prevent adverse effects[18].

Stage I: Dynamic Stabilization and CORE Strengthening

Goals of this stage:

  • Improving single-limb weight-bearing function to tolerate greater knee flexion angles.
  • Improving symmetry of lower extremity in running.
  • Enhancement of closed chain single-limb postural balance.

A strong CORE will allow the athlete to control the deceleration of the center of mass with balanced posture and accelerate their mass rapidly by controlled force. Weakness and deficits in trunk and hip musculature are correlated with biomechanical abnormalities and ACL injuries, particularly in female athletes[4][19].

Prior to CORE strengthening training, balance, proprioception and gait deviations should be well-addressed.

It is important to note that an athlete may have full anatomical ROM but with functional activities, asymmetries and deficits may be present[18]. Addressing these deficits will allow progression in speed and intensity of running without pain and re-injury. Deficits in rhythmic strides and symmetry can be detected by audible monitoring of foot contact. Pain, particularly patellofemoral pain, or ROM deficits are contributing factors to unbalanced sprinting gait. Backward gait is a way of decreasing patellofemoral pain and help the athlete to progress in this stage and may also increase quad strength[18].

Examples of exercises to be used in this stage:

Single leg dead lift.jpg Bilateral knee balance on BOSU.jpg
Bridge on BOSU.jpg Wall squat with stability ball.jpg

Each athlete will need individualized variations according to individual characteristics and sport.

Exercise intensity should be changed constantly to challenge balance and proprioception. Modifications of body posture, switching between various unstable surfaces, speed modifications, adding a sport-specific skill and/or adding unanticipated movement can all be ways of challenging stability and balance.

Stage II: Functional strengthening

Goals of this stage:

  • Increasing lower extremity non weight-bearing strength.
  • Improving load distribution pattern over both lower extremities in activities requiring double-leg stance.
  • Improvement of single-limb landing force attenuation strategies.

With CORE strengthening and dynamic stabilization exercises continuing throughout this stage, progressive lower extremity strengthening is introduced. Gradually and frequently adding more resistance without compromising good form.

Retrograde training, for example backward running on treadmill or backward jumping, has been shown to increase functional quadriceps activation and to limit patellofemoral pain[20][21]

Examples of exercises to be used in this stage:

Lateral step down BOSU.jpg Single leg squat BOSU.gif
Table-top crunches.gif Single leg bridges on BOSU.gif
Hamstrings curl on swiss ball.gif Lateral lunges.gif

Stage III: Power development

At this stage, power production of lower extremity is the main aim. Additionally, athletes are trained to resist fatigue and perform plyometrics with good biomechanics[18]. Training incorporates mid-level intensity double-limb multi-planar plyometric jumps and low-intensity single-limb hops.

Provide feedback and educate the athlete to land softly with coronal plane knee control.

Combining plyometrics with strength training improved jump performance and leg strength[22]. The addition of neuromuscular training with plyometrics, CORE and speed training resulted in great outcomes in performance measures[18].

Examples of exercises to be used in this stage:

Single leg X hop.jpg Barbell back squat.gif
Nordic hamstring curls.gif Lateral crunches.jpg
Forward and backward jump.gif Back extensio on swiss ball.jpg

Stage IV: Sport Performance Symmetry

At this stage athletes are trained to utilize safe biomechanics (increased knee flexion and decreased knee abduction angles with symmetrical forces and motions between limbs) in high-intensity plyometric exercises, produce symmetrical power between both lower extremities and learn to improve confidence to maintain dynamic knee stability with high-intensity change of direction activities[18].

Verbal and visual feedback are important at this stage.

Increased valgus angle is a factor contributing to injuries, particularly in females. Valgus loads on the knee can double during unanticipated cutting maneuvers. By teaching athletes to use movement techniques that produce low knee abduction moments during movements that can produce high loads on the joint, they can ultimately reduce the risk of injury[18].

Examples of exercises to be used in this stage:

Lunge jump.jpg
[23]
[24]
[25]
[26]
[27]

Return to Sport Criteria

Evidence of deficits in muscular strength and balance exist months after surgery in both ACL-reconstructed knee and contralateral limb[28]. Abnormal knee kinematics was found up to a year following surgery[29].

A systematic review by Barber-Westin and colleagues[28] investigated return to sport criteria in many studies and concluded that in order to give clearance to return to sport an athlete must have:

  • Less than 10% deficit in strength of the quadriceps and hamstring on isokinetic testing at 180°/s and 300°/s,
  • Less than 15% deficit in lower limb symmetry on single-leg hop testing (single hop, triple hop, crossover hop, and timed hop)
  • Less than 3 mm of increased anterior-posterior tibial displacement on Lachman or knee arthrometer testing,
  • Greater than 60% normalized knee separation distance on a video drop-jump test,
  • Absence of effusion
  • Full knee ROM
  • Normal patellar mobility,
  • No or only slight patellar crepitus,
  • Painless activities without swelling.
[30]
[31]

The International Knee Documentation Committee is a great tool to assess knee function and differentiate high knee function from low knee function[16].

Single-legged hop tests assess different measures such as performance, strength, neuromuscular control, confidence in the limb, and the ability to tolerate loads related to sports-specific activities. Specific deficits can be detected in these tests, allowing the clinician to tackle them in the rehabilitation plan and also give an idea on time to return to sport[16].

References

  1. Dunn WR, Spindler KP, Moon Consortium. Predictors of Activity Level 2 Years After Anterior Cruciate Ligament Reconstruction (ACLR) A Multicenter Orthopaedic Outcomes Network (MOON) ACLR Cohort Study. The American journal of sports medicine. 2010;38(10):2040-50.
  2. 2.0 2.1 Paterno MV, Rauh MJ, Schmitt LC, Ford KR, Hewett TE. Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport. The American journal of sports medicine. 2014;42(7):1567-73.
  3. Salmon L, Russell V, Musgrove T, Pinczewski L, Refshauge K. Incidence and risk factors for graft rupture and contralateral rupture after anterior cruciate ligament reconstruction. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2005;21(8):948-57.
  4. 4.0 4.1 4.2 4.3 Hewett TE1, Myer GD, Ford KR, Heidt RS Jr, Colosimo AJ, McLean SG, van den Bogert AJ, Paterno MV, Succop P. Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in female athletes: a prospective study. The American journal of sports medicine. 2005;33(4):492-501.
  5. Zazulak BT, Hewett TE, Reeves NP, Goldberg B, Cholewicki J. Deficits in neuromuscular control of the trunk predict knee injury risk: prospective biomechanical-epidemiologic study. The American journal of sports medicine. 2007;35(7):1123-30.
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  7. Castanharo R, Da Luz BS, Bitar AC, D’Elia CO, Castropil W, Duarte M. Males still have limb asymmetries in multijoint movement tasks more than 2 years following anterior cruciate ligament reconstruction. Journal of Orthopaedic Science. 2011;16(5):531.
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  12. 12.0 12.1 12.2 Grindem H, Snyder-Mackler L, Moksnes H, Engebretsen L, Risberg MA. Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med. 2016;50(13):804-8. doi: 10.1136/bjsports-2016-096031.
  13. Lentz TA, Zeppieri Jr G, George SZ, Tillman SM, Moser MW, Farmer KW, Chmielewski TL. Comparison of physical impairment, functional, and psychosocial measures based on fear of reinjury/lack of confidence and return-to-sport status after ACL reconstruction. The American journal of sports medicine. 2015;43(2):345-53.
  14. Everhart JS, Best TM, Flanigan DC. Psychological predictors of anterior cruciate ligament reconstruction outcomes: a systematic review. Knee Surgery, Sports Traumatology, Arthroscopy. 2015;23(3):752-62.
  15. Culvenor AG, Barton CJ. ACL injuries: the secret probably lies in optimising rehabilitation. Br J Sports Med. 2018;52(22):1416-1418. doi: 10.1136/bjsports-2017-098872
  16. 16.0 16.1 16.2 Logerstedt D, Grindem H, Lynch A, Eitzen I, Engebretsen L, Risberg MA, Axe MJ, Snyder-Mackler L. Single-legged hop tests as predictors of self-reported knee function after anterior cruciate ligament reconstruction: the Delaware-Oslo ACL cohort study. The American journal of sports medicine. 2012;40(10):2348-56.
  17. Lentz TA, Zeppieri Jr G, Tillman SM, Indelicato PA, Moser MW, George SZ, Chmielewski TL. Return to preinjury sports participation following anterior cruciate ligament reconstruction: contributions of demographic, knee impairment, and self-report measures. journal of orthopaedic & sports physical therapy. 2012;42(11):893-901.
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  21. Flynn TW, Soutas-Little RW. Patellofemoral joint compressive forces in forward and backward running. Journal of Orthopaedic & Sports Physical Therapy. 1995;21(5):277-82.
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  23. Tuck Jump. Available from: https://www.youtube.com/watch?v=zh1v8jINBZ0
  24. TFW Explosive Box Step Up. Available from:https://www.youtube.com/watch?v=KDwzB6xuZ9o
  25. Depth jump to box jump - Increase vertical jump - Volleyball. Available from: https://www.youtube.com/watch?v=5EztcmA0Amc
  26. Four Corner Drill. Available from: https://www.youtube.com/watch?v=HwPCpzLmSYQ
  27. SPEED TRAINING: Quick Cut "W" Drill. Available from: https://www.youtube.com/watch?v=hXNuP6ohxwQ
  28. 28.0 28.1 Barber-Westin SD, Noyes FR. Factors used to determine return to unrestricted sports activities after anterior cruciate ligament reconstruction. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2011;27(12):1697-705.
  29. Deneweth JM, Bey MJ, McLean SG, Lock TR, Kolowich PA, Tashman S. Tibiofemoral joint kinematics of the anterior cruciate ligament-reconstructed knee during a single-legged hop landing. The American journal of sports medicine. 2010;38(9):1820-8.
  30. ACL Prevention Screening: The Drop Jump Test. Available from:https://www.youtube.com/watch?v=5DrD-G4gWt8
  31. Triple hop for distance. Available from: https://www.youtube.com/watch?v=4Rp_BJUBQ6g