Keywords: ACL Reconstruction, Quadriceps Activation, Arthrogenic Muscle Inhibition

This blog is based on a recently published study that can be found here.

Early intervention can significantly improve post-surgery recovery. Learn the key techniques to enhance quadriceps activation and prevent long-term complications.

Introduction

Anterior cruciate ligament (ACL) injuries are common, particularly among athletes, and often require surgical reconstruction. A critical aspect of post-surgical recovery is addressing Arthrogenic Muscle Inhibition (AMI), a condition that prevents proper quadriceps activation. Without early and effective intervention, AMI can lead to persistent strength deficits, delayed recovery, and a heightened risk of re-injury. This blog discusses the importance of early quadriceps activation and highlights practical techniques to optimize rehabilitation.

Understanding Arthrogenic Muscle Inhibition (AMI) 

• AMI leads to a reduced motor neuron pool and impairs voluntary muscle contraction. [1–3]
• Persistent AMI can result in long-term muscle atrophy, delayed recovery, and altered biomechanics. [3–5]
• Addressing AMI early is essential to prevent these long-term consequences.[6–8]

Techniques to Improve Quadriceps Activation

Target the Muscle System

• BFR training: Blood flow restriction (BFR) training helps maintain muscle strength and prevent atrophy by promoting quadriceps activation under low loads, making it highly effective in the early stages of rehabilitation when AMI limits traditional strength training. [9–11]
• Hamstring fatigue exercise: Fatiguing the hamstrings can reduce reciprocal inhibition of the quadriceps, thereby aiding in overcoming AMI and facilitating better quadriceps activation during rehabilitation. [12–14]

Target the Central Nervous System

• Virtual reality can enhance patient motivation and adherence to therapy, potentially modulating cortical circuits and improving quadriceps activation by creating an immersive rehabilitation environment. [15]
• Cross-education therapy leverages the activation of the non-injured limb to improve strength and reduce inhibition in the affected limb, although its efficacy for AMI post-ACLR remains debated. [16–18]
• EMG Biofeedback with exercises provides real-time visual or auditory feedback to patients, helping them consciously activate the quadriceps and overcome AMI-related muscle inhibition. [19]
• Motor imagery: By mentally rehearsing muscle movements, motor imagery can enhance motor neuron excitability, aiding in the reactivation of inhibited quadriceps muscles post-ACLR. [12]
• Local vibration can stimulate the central nervous system and reduce AMI by increasing motor unit recruitment and improving voluntary quadriceps activation over time. [20]

Target the Peripheral Nervous System

• Neuromuscular Electrical Stimulation (NMES): NMES directly stimulates quadriceps muscle contractions by bypassing the inhibitory mechanisms of AMI, helping to restore strength and prevent muscle atrophy in the early stages of rehabilitation. [18,21,22]
• Transcutaneous Electrical Nerve Stimulation (TENS) reduces pain and inhibits the sensory signals that contribute to AMI, temporarily restoring motor neuron excitability and improving quadriceps activation. [18,21,22]
• Cryotherapy decreases pain and swelling, which mitigates the reflex inhibition caused by AMI, improving muscle activation and facilitating quadriceps strengthening. [23–26]
• Percutaneous electrical stimulation: This technique stimulates specific nerve pathways to overcome AMI by directly enhancing quadriceps contraction, leading to reduced inhibition and increased strength.

Clinical Signs and Levels of Quadriceps Activation

• Minimal Activation: Basic muscle contraction with full knee extension. [27–29]
• Adequate Activation: Full knee extension during specific activities.

Fast Activation: Crucial for advanced phases of rehabilitation and return to sports. [30–33]

Conclusion

Early and targeted interventions are vital for addressing quadriceps activation post-ACLR. By integrating a multimodal approach that includes muscle, brain, and nerve-targeting therapies, clinicians can help patients regain strength and function more effectively. Recognizing the signs of AMI and applying evidence-based therapies can significantly reduce long-term complications and improve the rate of return to sport.

KEY POINTS

• Early quadriceps activation is crucial to overcoming AMI.
• A combination of muscle activation techniques, pain management, and neuromuscular therapies can optimize recovery.
• Proper clinical assessment is necessary to customize rehabilitation strategies.
• Properly identifying the patient’s level of activation is essential to prevent complications and ensure a successful return to activity.

AUTHORS

Ayrton MOIROUX-SAHRAOUI1,2,3, Florian FORELLI1,2,3,4, Jean MAZEAS1,2, Alexandre JM RAMBAUD4,5, Andreas BJERREGAARD6, Jérôme RIERA7,8

1. Orthosport Rehab Center, Domont, France 
2. Orthopaedic Surgery Department, Clinic of Domont, Ramsay Healthcare, @OrthoLab, Domont, France
3. Physiotherapy School, IPMR, Nevers, France
4. SFMK Lab, Pierrefite sur seine, France 
5. Physiotherapy School of Saint Etienne, St Michel Campus, Saint Etienne, France 
6. Rehabilitation Department, Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar
7. University Jean Monnet Saint-Etienne, Lyon 1, University Savoie Mont-Blanc, Inter-university Laboratory of Human Movement Biology, EA 7424, F-42023, Saint-Etienne, France 
8. University of Bordeaux, College of Health Sciences, IUSR, 33000, Bordeaux, France

REFERENCES

1 Iles JF, Stokes M, Young A. Reflex actions of knee joint afferents during contraction of the human quadriceps. Clin Physiol. 1990;10:489–500. doi: 10.1111/j.1475-097X.1990.tb00828.x

2 Norte G, Rush J, Sherman D. Arthrogenic Muscle Inhibition: Best Evidence, Mechanisms, and Theory for Treating the Unseen in Clinical Rehabilitation. J Sport Rehabil. 2022;31:717–35. doi: 10.1123/jsr.2021-0139

3 Lepley LK, Wojtys EM, Palmieri-Smith RM. Combination of eccentric exercise and neuromuscular electrical stimulation to improve quadriceps function post-ACL reconstruction. The Knee. 2015;22:270–7. doi: 10.1016/j.knee.2014.11.013

4 Chung KS, Ha JK, Yeom CH, et al. Are Muscle Strength and Function of the Uninjured Lower Limb Weakened After Anterior Cruciate Ligament Injury?: Two-Year Follow-up After Reconstruction. Am J Sports Med. 2015;43:3013–21. doi: 10.1177/0363546515606126

5 Sherman DA, Rush J, Stock MS, et al. Neural drive and motor unit characteristics after anterior cruciate ligament reconstruction: implications for quadriceps weakness. PeerJ. 2023;11:e16261. doi: 10.7717/peerj.16261

6 Lewek M, Rudolph K, Axe M, et al. The effect of insufficient quadriceps strength on gait after anterior cruciate ligament reconstruction. Clin Biomech. 2002;17:56–63. doi: 10.1016/S0268-0033(01)00097-3

7 Pietrosimone B, Loeser RF, Blackburn JT, et al. Biochemical markers of cartilage metabolism are associated with walking biomechanics 6‐months following anterior cruciate ligament reconstruction. J Orthop Res. 2017;35:2288–97. doi: 10.1002/jor.23534

8 Grindem H, Snyder-Mackler L, Moksnes H, et al. Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med. 2016;50:804–8. doi: 10.1136/bjsports-2016-096031

9 DePhillipo NN, Kennedy MI, Aman ZS, et al. The Role of Blood Flow Restriction Therapy Following Knee Surgery: Expert Opinion. Arthrosc J Arthrosc Relat Surg. 2018;34:2506–10. doi: 10.1016/j.arthro.2018.05.038

10 Curran MT, Bedi A, Mendias CL, et al. Blood Flow Restriction Training Applied With High-Intensity Exercise Does Not Improve Quadriceps Muscle Function After Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial. Am J Sports Med. 2020;48:825–37. doi: 10.1177/0363546520904008

11 Hughes L, Rosenblatt B, Haddad F, et al. Comparing the Effectiveness of Blood Flow Restriction and Traditional Heavy Load Resistance Training in the Post-Surgery Rehabilitation of Anterior Cruciate Ligament Reconstruction Patients: A UK National Health Service Randomised Controlled Trial. Sports Med. 2019;49:1787–805. doi: 10.1007/s40279-019-01137-2

12 Norte G, Rush J, Sherman D. Arthrogenic Muscle Inhibition: Best Evidence, Mechanisms, and Theory for Treating the Unseen in Clinical Rehabilitation. J Sport Rehabil. 2022;31:717–35. doi: 10.1123/jsr.2021-0139

13 Lowe T, Dong XN. The Use of Hamstring Fatigue to Reduce Quadriceps Inhibition After Anterior Cruciate Ligament Reconstruction. Percept Mot Skills. 2018;125:81–92. doi: 10.1177/0031512517735744

14 Yu S, Lowe T, Griffin L, et al. Single bout of vibration-induced hamstrings fatigue reduces quadriceps inhibition and coactivation of knee muscles after anterior cruciate ligament (ACL) reconstruction. J Electromyogr Kinesiol Off J Int Soc Electrophysiol Kinesiol. 2020;55:102464. doi: 10.1016/j.jelekin.2020.102464

15 Flórez Fonnegra JP, Pino Prestan AC, López LL, et al. Rehabilitation of Patients with Arthrogenic Muscular Inhibition in Pathologies of Knee Using Virtual Reality. Sensors. 2023;23:9114. doi: 10.3390/s23229114

16 Harput G, Ulusoy B, Yildiz TI, et al. Cross-education improves quadriceps strength recovery after ACL reconstruction: a randomized controlled trial. Knee Surg Sports Traumatol Arthrosc Off J ESSKA. 2019;27:68–75. doi: 10.1007/s00167-018-5040-1

17 Zult T, Gokeler A, van Raay JJAM, et al. Cross-education does not accelerate the rehabilitation of neuromuscular functions after ACL reconstruction: a randomized controlled clinical trial. Eur J Appl Physiol. 2018;118:1609–23. doi: 10.1007/s00421-018-3892-1

18 Kotsifaki R, Korakakis V, King E, et al. Aspetar clinical practice guideline on rehabilitation after anterior cruciate ligament reconstruction. Br J Sports Med. 2023;57:500–14. doi: 10.1136/bjsports-2022-106158

19 Ananías J, Vidal C, Ortiz-Muñoz L, et al. Use of electromyographic biofeedback in rehabilitation following anterior cruciate ligament reconstruction: a systematic review and meta-analysis. Physiotherapy. 2024;123:19–29. doi: 10.1016/j.physio.2023.12.005

20 Souron R, Besson T, Millet GY, et al. Acute and chronic neuromuscular adaptations to local vibration training. Eur J Appl Physiol. 2017;117:1939–64. doi: 10.1007/s00421-017-3688-8

21 Sonnery-Cottet B, Saithna A, Quelard B, et al. Arthrogenic muscle inhibition after ACL reconstruction: a scoping review of the efficacy of interventions. Br J Sports Med. 2019;53:289–98. doi: 10.1136/bjsports-2017-098401

22 Conley CEW, Mattacola CG, Jochimsen KN, et al. A Comparison of Neuromuscular Electrical Stimulation Parameters for Postoperative Quadriceps Strength in Patients After Knee Surgery: A Systematic Review. Sports Health. 2021;13:116–27. doi: 10.1177/1941738120964817

23 Hopkins J, Ingersoll CD, Edwards J, et al. Cryotherapy and Transcutaneous Electric Neuromuscular Stimulation Decrease Arthrogenic Muscle Inhibition of the Vastus Medialis After Knee Joint Effusion. J Athl Train. 2002;37:25–31.

24 Effects of cryotherapy on arthrogenic muscle inhibition using an experimental model of knee swelling. doi: 10.1002/art.24168

25 Hart JM, Kuenze CM, Diduch DR, et al. Quadriceps Muscle Function After Rehabilitation With Cryotherapy in Patients With Anterior Cruciate Ligament Reconstruction. J Athl Train. 2014;49:733–9. doi: 10.4085/1062-6050-49.3.39

26 Kuenze C, Eltoukhy M, Kelly A, et al. Impact of quadriceps strengthening on response to fatiguing exercise following ACL reconstruction. J Sci Med Sport. 2017;20:6–11. doi: 10.1016/j.jsams.2016.04.015

27 Williams GN, Barrance PJ, Snyder-Mackler L, et al. Altered Quadriceps Control in People with Anterior Cruciate Ligament Deficiency: Med Sci Sports Exerc. 2004;36:1089–97. doi: 10.1249/01.MSS.0000131959.20666.11

28 Lobo Júnior P, Barbosa Neto IA, Borges JHDS, et al. CLINICAL MUSCULAR EVALUATION IN PATELLOFEMORAL PAIN SYNDROME. Acta Ortopédica Bras. 2018;26:91–3. doi: 10.1590/1413-785220182602187215

29 Ward SH, Blackburn JT, Padua DA, et al. Quadriceps Neuromuscular Function and Jump-Landing Sagittal-Plane Knee Biomechanics After Anterior Cruciate Ligament Reconstruction. J Athl Train. 2018;53:135–43. doi: 10.4085/1062-6050-306-16

30 Angelozzi M, Madama M, Corsica C, et al. Rate of Force Development as an Adjunctive Outcome Measure for Return-to-Sport Decisions After Anterior Cruciate Ligament Reconstruction. J Orthop Sports Phys Ther. 2012;42:772–80. doi: 10.2519/jospt.2012.3780

31 Suzuki M, Ishida T, Samukawa M, et al. Rate of Torque Development in the Quadriceps after Anterior Cruciate Ligament Reconstruction with Hamstring Tendon Autografts in Young Female Athletes. Int J Environ Res Public Health. 2022;19:11761. doi: 10.3390/ijerph191811761

32 Maestroni L, Read P, Turner A, et al. Strength, rate of force development, power and reactive strength in adult male athletic populations post anterior cruciate ligament reconstruction – A systematic review and meta-analysis. Phys Ther Sport. 2021;47:91–104. doi: 10.1016/j.ptsp.2020.11.024

33 Hunnicutt JL, McLeod MM, Slone HS, et al. Quadriceps Neuromuscular and Physical Function After Anterior Cruciate Ligament Reconstruction. J Athl Train. 2020;55:238–45. doi: 10.4085/1062-6050-516-18