Psychological Predictors of Anterior Cruciate Ligament Recovery Outcomes

Introduction

Anterior cruciate ligament (ACL) injury occurs most frequently in active individuals. Often ACL deficiency does not allow an individual to continue participation in sports at the same level. One of the primary early objectives of ACL reconstruction is to allow an injured individual to return to an active lifestyle and often a specific sporting activity. Despite the advancements in ACL reconstruction techniques and rehabilitation, fewer than 50% of patients return to their prior level of activity.

The reasons patients do not return to sport after ACL reconstruction are multifactorial. Demographics, age, subjective and objective knee function, and incomplete rehabilitation are all possible contributing factors. In addition, a growing body of evidence suggests psychological factors significantly contribute to an individual’s success or failure in returning to sport after ACL reconstruction. Similar associations between patient psychosocial factors and surgical outcomes have been observed in other areas of orthopaedics as well, such as recovery after spinal fusion and total knee or hip arthroplasty.

Recent qualitative studies of patients after ACL reconstruction who did not return to preinjury activity levels demonstrate several major self-reported reasons for decreased activity levels even after completion of a rehabilitation program. Tjong et al. recently conducted a study in which they interviewed patients 2 years after ACL reconstruction and identified three predominant themes at play in an individual’s decision to return to sport despite having a stable, recovered knee: fear of reinjury (kinesiophobia), shifts in priorities (social considerations), and individual personality traits. In this chapter we will focus on these three key psychosocial elements; we will review the current literature on each topic and will describe how each has been shown to be predictive of return to sport (or lack of return to sport) after ACL reconstruction. Finally, we will discuss the possibility that addressing psychological factors in ACL reconstruction may potentially improve return to sport rates.

Fear of Reinjury/Kinesiophobia

The concept of avoidance learning seen in patients with chronic pain was put forth in the early 1980s and describes behaviors that are undertaken in order to prevent aversive consequences. Since that time, the fear avoidance model has been used to explain how psychological factors affect the experience of pain. It has predominately been used to describe patients who suffer from low back pain, but has been used with other forms of chronic musculoskeletal complaints. The model describes patients who develop negative, catastrophizing beliefs about pain, which leads them into a cycle of fear, activity avoidance, and resultant disuse and distress. In this way, it has been said that the fear of pain, injury, or reinjury can be more disabling than the pain itself. This type of fear, coined kinesiophobia , is described as an irrational and debilitating fear of physical movement resulting from a feeling of vulnerability to painful injury or re-injury. The alternative and successful coping mechanism seen after a pain experience does not involve fear, but is contingent upon a patient confronting his or her pain.

To explain the fear associated with an ACL injury, one patient reported, If you got into a bad car accident on a highway, then you may not drive on that road again. That’s how I feel about my ACL. Statements from patients like these have caused many investigators to consider the role that fear plays in the recovery of ACL reconstruction patients. Kvist et al. was the first to examine the role of kinesiophobia in individuals with ACL injury. They administered a modified Tampa Scale of Kinesiophobia (TSK) to quantify kinesiophobia, and found that patients who did not return to their previous level of activity had significantly higher TSK scores than those that did. Furthermore, they found that increased fear of movement was related to worse knee pain and quality of life in individuals 2–4 years after ACL reconstruction. Since this initial report, interest in this area of recovery has tremendously increased.

Evidence that fear of reinjury has an adverse effect on return to sport and activity after ACL reconstruction continues to grow. This statement is supported by studies that measured fear of reinjury among individuals who did and did not return to their prior level of sport. One year after surgery, Tripp et al. found patients who had the most concerns about suffering further injury had lower levels of participation in their sport. Individuals who return to sport consistently report less fear of movement and reinjury than individuals who do not return to their prior level of activity at one year post ACL reconstruction, and these differences persist even 7 years later.

Aside from reductions in return to prior level of sport rates, other mid- and long-term outcomes are adversely impacted by fear of movement and reinjury. Higher fear of movement and reinjury contributes to worse self-reported knee function as measured by the Knee Injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) Subjective Knee Form from 6 months up to 4 years post ACL reconstruction. Furthermore, recent studies suggest individuals with higher fear demonstrate lower performance in measures of function, such as muscle strength testing and single leg hop testing. Further research is needed to understand how fear of movement and reinjury impact knee function.

Ideally, a clinician would be able to screen ACL reconstruction patients to identify which of them will be negatively affected in their recovery by fear of reinjury. Unfortunately, a recent systematic review on psychological predictors of ACL reconstruction outcomes by Everhart et al. determined that no such instrument currently exists. There is recent evidence that suggests fear of reinjury lessens early in rehabilitation, with time, and may be amenable to intervention, but it is unclear when and for whom further psychological intervention is warranted. Further research is required to determine mechanisms to identify patients at risk for adverse ACL reconstruction outcomes due to high fear, create interventions to reduce irrational fear of movement, and determine if addressing this fear of reinjury will improve long-term outcomes, including successful return to sport.