The psychology of returning to sports after ACL surgery

By Trevor A. Lentz, PT, SCS, CSCS

Psychological factors are responsible for delayed return to sports after anterior cruciate ligament reconstruction in a sig­nificant number of patients despite successful physical rehabilitation, but questions remain as to the most effective ways to address these issues.

Anterior cruciate ligament (ACL) rupture is a common sports-related injury, with multiple physical, psychological, economic, and social consequences. Those who suffer an ACL tear often choose to undergo surgical reconstruction, as this is thought to provide the best chance of returning to unrestricted sports participation.^1,2 Indeed, the development of arthroscopic reconstruction techniques and the subsequent emergence of accelerated rehabilitation protocols have made return to preinjury levels of sports participation a very realistic possibility for most patients.^3-5 But how effective are we as sports medicine professionals at returning patients to preinjury levels of sports participation and performance?

Recent studies have clarified the current state of return to sport following ACL reconstruction, and the results are discouraging. In a large meta-analysis, Ardern et al⁶ found that, while 81% of people returned to some level of sport after surgery, only 65% returned to their preinjury level of sport and 55% returned to competitive sports after surgery. Many studies have identified potentially modifiable factors as a primary barrier to return-to-sports participation. These potentially modifiable factors often include psychological factors.^7-10 In fact, psychological factors are often the most prevalent reason for not returning to sports, with numerous studies reporting that roughly half of those who do not return to sports, or approximately 20% of all patients undergoing ACL reconstruction, cite psychological factors as a primary reason.^7,8,10-12

Psychological factors as a barrier

The prevalence of psychological factors inhibiting return to sport is not surprising. Across other anatomical regions and diagnoses, psychological factors are regarded as some of the strongest and most consistent predictors of pain and disability, often more so than commonly assessed physical factors.^13-16 More surprising, however, is that most established ACL rehabilitation guidelines and return-to-sport criteria fail to include specific assessment or intervention recommendations for psychological factors,^17-20 and these factors are not often recognized by clinicians as barriers to sports participation.²¹

The relatively high prevalence of psychological factors as a barrier to sports participation may be due to many reasons. First, accelerated rehabilitation programs that place a heavy emphasis on early range of motion, weightbearing, quadriceps strengthening, and neuromuscular retraining have reduced the risk of developing physical limitations that impede sports participation. Patients are typically allowed to begin sport-specific training three to four months after reconstruction, and get clearance for return to unrestricted sports participation around six to nine months postsurgery.²⁰ However, as a result of these impairment-focused accelerated rehabilitation programs, our ability to consistently provide patients with a strong, stable knee has outpaced our ability to consistently provide them with psychological readiness, thus leading to a relatively higher prevalence of psychological barriers.

Another reason for the relatively high prevalence of psychological barriers is that surgical success has historically been defined by objective outcomes (eg, knee ligament laxity, graft integrity, knee range of motion, knee strength), with less attention on the ability to return to sports. Presumably, this focus has been the result of inherent difficulties in quantifying return to sports, or the assumption that resolution of objective knee impairments necessarily facilitates a return to unrestricted sports participation. However, multiple studies have now shown that resolution of knee impairments is a poor proxy for return-to-sport status.^10,22 For instance, Ardern et al found that, while 90% of people undergoing ACL reconstruction achieved normal or nearly normal knee function postoperatively (mean, 41.5 months) using impairment-based outcomes, only 63% had returned to their preinjury level of participation, and 44% had returned to competitive sports.¹⁰

The extent to which variance in return-to-sports outcomes is not explained by physical factors commonly addressed in rehabilitation provides a compelling argument for reevaluating whether our current rehabilitation approaches and return-to-sports criteria that focus on objective outcomes should also include consideration of psychological factors.

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Psychological contributors

The concept of psychological factors as barriers to return to sports is not new.^23,24 In the mid-1980s, researchers applied grief and loss and cognitive appraisal models to sports-related injury to describe psychological adjustments and emotional responses throughout recovery.²³ In the mid-to-late 1990s, specific considerations emerged for psychological responses to ACL injury and reconstruction.²³ Since then, our understanding of psychological factors as they contribute to poor sports performance and the ability to return to sports following injury has grown considerably.²⁵

Fear-avoidance beliefs. “Fear-avoidance beliefs” is a broad term referring to the avoidance of activities based on fear.²⁶ In patients who have undergone ACL reconstruction, the most common fear-avoidance beliefs are those regarding fear of movement (kinesiophobia) and fear of pain. The fear avoidance model has been proposed to describe the development of fear of pain, anxiety, and disability as the result of a painful experience or injury.²⁷ A full description is beyond the scope of this article; interested readers are referred to reviews by Vlaeyen and Linton and Leeuw et al.^27,28

While the fear-avoidance beliefs model was initially developed to describe the transition from acute to chronic pain in patients with low back pain, the inherently painful and destabilizing nature of an ACL injury lends itself to the theoretical application of this model in patients who have undergone ACL reconstruction, and recent studies provide empirical and statistical evidence to support the validity of the fear avoidance model in this population.^29,30

Empirical support for the fear avoidance model is found in numerous studies reporting on self-described reasons for not returning to sports. Many of these have found that fear of reinjury is the most common reason for not returning to sports, more common than knee instability or pain.^2,7,8,10 Other studies have identified fear avoidance beliefs as a significant contributor to knee function in multivariate analysis. Ross et al³¹ showed that fear avoidance beliefs related to physical activity contributed significantly to knee function and sports-related activity after ACL reconstruction, even after accounting for injury-related variables and physical impairment measures.

A similar study by our research group found that kinesiophobia was a significant contributor to self-reported function in a multivariate analysis, after accounting for common physical impairment and demographic variables in patients who had been cleared for return to sports at six months and one year post-ACL reconstruction.³² In a cross-sectional study of patients within the first year of ACL reconstruction, Chmielewski et al found higher levels of kinesiophobia in the first three months after surgery than after six months; however, kinesiophobia after six months was significantly associated with knee function.³³ This study included patients in both the early postoperative and late return-to-sports stages of rehabilitation and did not distinguish between patients who had and had not been cleared to return to sports in the late stage. Collectively, these findings suggest that fear-avoidance beliefs contribute to functional limitations following ACL reconstruction and should be considered a target for rehabilitation after surgery.

Pain catastrophizing. Knee pain typically decreases over time following ACL reconstruction, and is generally low in the late postsurgical stages of rehabilitation.^9,33 However, despite relatively low levels of pain following surgery, the presence of pain is a common impairment-related barrier to sports participation and a significant predictor of function throughout rehabilitation.^9,11,33 In addition to fear of pain, pain catastrophizing may be one mechanism by which even low levels of pain can contribute to significant functional limitations following ACL reconstruction.

Pain catastrophizing is an exaggerated response to actual or anticipated pain.³⁴ Catastrophizing behavior as it relates to pain is one of the central mechanisms driving avoidance behavior in the fear-avoidance model and may be a significant factor for people following ACL reconstruction who have pain or anticipate pain as the result of a functional activity. Clinical studies have identified pain catastrophizing as a significant predictor of pain intensity in the early postsurgical phases of rehabilitation; however, its influence on function in later stages of rehabilitation, including return to sports, is not as clear.^30,35 Pilot data suggest early postoperative and one-year differences in pain catastrophizing between patients who return to sports after ACL reconstruction and those who do not due to fear of reinjury, but those data require confirmation in larger studies.³⁶

Psychological resilience. While most studies have focused on negative factors that confer psychological vulnerability to injury or pain, less attention has been paid to positive factors that enable patients to adaptively cope with their injury or pain. Positive psychological resources, such as self-efficacy or optimism, may have a significant influence on return to sports after ACL reconstruction and should be considered an important adaptive psychological factor. Chmielewski et al,³⁰ for example, found that early improvements in self-efficacy following surgery were associated with greater reductions in pain and function, while other studies have linked preoperative resilience factors—such as psychological readiness to return to sports (measured with the ACL-Return to Sport after Injury [ACL-RSI] scale, internal locus of control, and positive expectations—with significantly higher odds of returning to sports.³⁷

In a systematic review of psychological predictors of ACL outcomes, Everhart et al³⁸ found that early measures of self-efficacy, self-motivation, and optimism were predictive of return to sports and knee function. Resilience factors are independent of negative psychological factors, such as fear avoidance and catastrophizing, and therefore should be assessed and addressed independently in the clinical encounter.

Identifying patients at risk

Recovery of function and sports performance following ACL reconstruction is a multidimensional, complex process. For some patients, psychological factors may represent a significant barrier to regaining knee function or sports performance. Others will not have any significant psychological barriers. One of the most important limitations in our current knowledge is how to prospectively identify patients who are at risk for poor return-to-sports outcomes due to psychological factors.

Unfortunately, no threshold values have been firmly established for psychological questionnaires when determining risk for failure to return to sports after ACL reconstruction. Some studies, however, have reported questionnaire means for groups of patients who do not return to sport, and these provide some direction for identifying patients with elevated fear of reinjury.

Our research group found that patients who were unable to return to sports had mean scores of 20 points on the Tampa Scale for Kinesiophobia (TSK-11), while their counterparts who were able to return to sports reported mean scores of 15 points.⁸ Those who were unable to return to sports due to fear of reinjury, specifically, scored slightly higher, with a mean of 21.5 points.⁹ A small pilot study examining TSK-11 cut-off scores found that decreased odds of returning to sports after ACL reconstruction were associated with TSK-11 scores greater than 19 points; this threshold, however, should be confirmed in larger studies.³⁹ In addition to the TSK-11,⁴⁰ other questionnaires that may be used to assess psychological factors include the Pain Catastrophizing Scale (PCS),³⁴ Knee Self-Efficacy Scale (K-SES),⁴¹ and ACL-RSI scale.⁴² Based on available evidence, psychological factors should be evaluated early on in rehabilitation, tracked throughout the rehabilitation process, and assessed as a criterion for return to sports.

There is limited information specific to ACL injury populations that can be used to drive evidence-based recommendations for psychological treatment approaches. However, extensive research on treatment of patients with low back pain may provide some guidance. In low back pain populations, psychologically informed practice has been presented as a secondary prevention approach for the development of chronic pain and disability. Briefly, this approach incorporates screening for psychological factors and implementation of cognitive behavioral approaches into activity-based interventions. Interested readers may refer to a review by Nicholas and George for more information on this approach.⁴³

Psychologically informed prac­tice has shown promise for improving function in patients with low back pain who display clear signs of fear of pain or reinjury,⁴⁴ and may be beneficial for patients demonstrating similar issues following ACL reconstruc­- ­tion. However, this approach has not been examined in the published literature involving clinical trials of ACL reconstruction. Unfortunately, researchers and clinicians have a limited understanding of when negative psychological factors emerge and how they change over time. It stands to reason, however, that psychologically informed practice approaches may be most beneficial if started early in rehabilitation and continued through return-to-sports stages for patients with high levels of fear-avoidance beliefs, high levels of catastrophizing, or low psychological resilience.

Perhaps the most important aspect of evaluating and managing psychological factors following ACL reconstruction is for clinicians simply to talk with patients about this potential barrier. For some patients, early education on the healing process and risk factors for reinjury may help relieve fears that develop shortly after surgery. Discussing pain mechanisms and the expectation that recovery can take many months may help to reduce the early catastrophizing that often accompanies the experience of pain.

Often, the best way to assess specific psychological barriers is to ask. Most patients will discuss activities or movements that elicit fear, and graded exposure to these movements may be a good way to reduce those fears and improve self-efficacy. For other patients, return to sports may not be a priority. In fact, a sizeable percentage of patients do not return to sports after ACL reconstruction due to a change in lifestyle or a change in priorities.^2,7,8 Ultimately, establishing realistic goals and expectations, as well as maintaining open communication between patient and clinician, can go a long way toward assessing and managing psychological barriers in rehabilitation.

Trevor Lentz, PT, SCS, CSCS, is a physical therapist specializing in sports and postoperative rehabilitation at the University of Florida Health Orthopaedics and Sports Medicine Institute in Gainesville. His research focuses on the psychosocial influences of treatment effectiveness in patients with musculoskeletal pain.

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