The Anterior Cruciate Ligament (ACL) is the band of tissue that connects one’s femur to one’s tibia. Owing to its crucial – pun intended – location and function, damage to the ACL in any form is many athletes’ greatest fear . This is especially so for athletes whose sports or activities put excessive stress on the knees by demanding sudden stops or changes in direction . There are several articles we’ve published about the risk factors of ACL injuries and the long-term consequences of ACL reconstruction. Here, however, we delve into one major consequence of great personal and medical significance: pain. Research has found that post ACL reconstructive surgery, patients’ fear of movement, confidence in their knee, psychological preparedness to return to their sport, and pain are all related to function . Given that pain is one such important consequence, there have been significant investigations into its extent post ACL reconstruction.
Wasserstein and colleagues conducted primary research in 2015 investigating the prevalence of knee pain post ACL reconstruction . They developed three models to define “painful or symptomatic knee” based on the Knee Injury and Osteoarthritis Outcome Score (KOOS) related quality of life: Model #1 (≤87.5), Model #2 (≤72), Model #3 (a drop of 10 points from the original score on the KOOS scale 2-6 years after the surgery), and Model #4 (level of pain during activity). Of their 1530 patients, at the two years follow up mark, 43% and 9% fell into Models #1 and #2 respectively. At the six year follow up mark, whilst the percentages fell slightly for Models #1 and #2, 12% and 11% fell into Models #3 and #4 respectively. These results suggest that even 6 years post ACL reconstruction, several athletes still report significant knee pain. The researchers identify subsequent ipsilateral knee surgery as the most consistent risk factor for patients to fall into Models #3 or #4. They also comment on the correlation between less activity and higher reporting of pain but note that the direction of causation is unknown thus far.
Additionally, in 2017, primary research by Buescu and colleagues investigated whether autografts from different parts of the body during ACL reconstruction impacted pain post surgery . Autografts were taken from either the free quadriceps tendon or the hamstring tendon. Pain level was measured via the Visual Analog Scale and analgesic consumption in the immediate postoperative period. They found that patients who had autografts from the hamstring tendon experienced more pain than those from free quadriceps tendon. They suggest that they obtained these results because the harvest technique of the free quadriceps tendon is less invasive.
Another possible correlate of the pain is the comorbid knee osteoarthritis that develops after ACL reconstruction . Chmielewski and colleagues conducted research that points towards urinary CTX-II being as a biomarker and predictor of knee osteoarthritis and therefore, pain. A reduction of u-CTX-II was correlated with reduced knee pain and improved function. They recommend more research on u-CTX-II’s role as a prognostic marker.
Research has suggested that a certain predictor of patellofemoral pain 12 months after ACL reconstructive surgery from the hamstring tendon is age at the time of surgery . This finding is also corroborated by another study wherein patients older than 35 had a higher likelihood of developing cartilage injury . In terms of pain management, one study found that a ketorolac regimen is more effective than opioid drugs in reducing pain and with fewer side effects .
Lastly, the extant literature highlights the importance of performing reconstructive surgery sooner rather than later to mitigate post-operative pain and better prevent reinjury. Fok and Yau (2012) found that patients who had reconstructive surgery after a year of injury were more likely to develop meniscus injury or the meniscus injury was less likely to be repairable .
Thus, pain post ACL reconstruction depends on the age of the individual, how long after injury they receive surgery, various biomarkers, comorbidities, the location of allograft, etc. Biomedical pain management regimens include opioid and/or ketorolac medications. Individuals who experience pain post ACL reconstruction also experience higher body mass index, poor physical performance, quality of life, fear of movement, and a fear to return to their sport . These physiological and psychological explanations are all the more reason that patients who report pain after their ACL surgery should be advised and treated accordingly.
1. Mayo Clinic. (2021, March 10). ACL injury. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/acl-injury/symptoms-causes/syc-20350738.
2. Hart, H. F., Culvenor, A. G., Guermazi, A., &; Crossley, K. M. (2020). Worse knee confidence, fear of movement, psychological readiness to return-to-sport and pain are associated with worse function after ACL reconstruction. Physical Therapy in Sport, 41, 1–8. https://doi.org/10.1016/j.ptsp.2019.10.006
3. Wasserstein, D., Huston, L. J., Nwosu, S., Spindler, K. P., Kaeding, C. C., Parker, R. D., Wright, R. W., Andrish, J. T., Marx, R. G., Amendola, A., Wolf, B. R., McCarty, E. C., Wolcott, M., &; Dunn, W. R. (2015). KOOS pain as a marker for significant knee pain two and six years after primary ACL reconstruction: a Multicenter Orthopaedic Outcomes Network (MOON) prospective longitudinal cohort study. Osteoarthritis and Cartilage, 23(10), 1674–1684. https://doi.org/10.1016/j.joca.2015.05.025
4. Buescu, C. T., Onutu, A. H., Lucaciu, D. O., &; Todor, A. (2017). Pain level after ACL reconstruction: A comparative study between free quadriceps tendon and hamstring tendons autografts. Acta Orthopaedica Et Traumatologica Turcica, 51(2), 100–103. https://doi.org/10.1016/j.aott.2017.02.011
5. Chmielewski, T. L., Trumble, T. N., Joseph, A.-M., Shuster, J., Indelicato, P. A., Moser, M. W., Cicuttini, F. M., &; Leeuwenburgh, C. (2012). Urinary CTX-II concentrations are elevated and associated with knee pain and function in subjects with ACL reconstruction. Osteoarthritis and Cartilage, 20(11), 1294–1301. https://doi.org/10.1016/j.joca.2012.07.014
6. Culvenor, A. G., Collins, N. J., Vicenzino, B., Cook, J. L., Whitehead, T. S., Morris, H. G., &; Crossley, K. M. (2016). Predictors and effects of patellofemoral pain following hamstring-tendon ACL reconstruction. Journal of Science and Medicine in Sport, 19(7), 518–523. https://doi.org/10.1016/j.jsams.2015.07.008
7. Fok, A. W., &; Yau, W. P. (2012). Delay in ACL reconstruction is associated with more severe and painful meniscal and chondral injuries. Knee Surgery, Sports Traumatology, Arthroscopy, 21(4), 928–933. https://doi.org/10.1007/s00167-012-2027-1
8. McGuire, D. A., Sanders, K., &; Hendricks, S. D. (1993). Comparison of ketorolac and opioid analgesics in postoperative ACL reconstruction outpatient pain control. Arthroscopy: The Journal of Arthroscopic &; Related Surgery, 9(6), 653–661. https://doi.org/10.1016/s0749-8063(05)80501-8