Central Sensitization Symptoms and Psychosocial Factors in Athletes After ACL Reconstruction

The Central Sensitization Inventory (CSI) was used to assess symptoms of central sensitization. CSI was developed as a tool to evaluate somatic and emotional complaints associated with central sensitization syndrome. The CSI consists of 25 questions and can be divided in four sections that focus on physical symptoms, emotional distress, headache and jaw symptoms and urological symptoms (Mayer et al. 2012). Each question is answered on a 0-4 scale by choosing the intensity that best describes their symptoms or emotions. The individual answers are added to form a total score that can range from 0 to 100.

The Numerical Rating Scale (NRS) was used to assess pain intensity. NRS has been widely used to measure and assess pain levels in adults, including chronic pain patients (Hawker et al. 2011). The scale consists of a segmented numeric version of the Visual Analog Scale (VAS) in which subjects choose a number (0-10) that best describes their pain intensity.

Pain catastrophizing was assessed by the Pain Catastrophizing Scale (PCS). PCS was created in an effort to measure inability to cope with pain due to catastrophizing. The scale was developed on the construct that catastrophizing involves three subsequent dimensions, rumination, magnification and helplessness (Craner et al. 2016). It is a self-report questionnaire which includes 13 items about the above three dimensions of pain catastrophizing. Every item is answered on a Likert scale ranging from 0 to 4. A final total score will range between 0 and 52 points with minimal detectable change being 9 points.

Kinesiophobia was assessed using the Tampa Scale for Kinesiophobia (TSK). TSK is a questionnaire which consists of 17 questions and is used to assess fear of movement and re injury. The questions are answered by choosing the statement that most accurately represents the subjects state, these answers vary from "strongly agree" to "strongly disagree". The final score of the questionnaire will range from 17-68 and is made up by scoring each answer in a Likert scale (Lundberg et al. 2011).

Sense of unfairness was examined by using the Inequality Experience Questionnaire (IEQ) which is a 12-item scale that asks participants to indicate the frequency with which they experience different thoughts concerning the sense of unfairness corelated to their injury on a five-point scale ranging from 0 (never) to 4 (all the time). The IEQ yields two factors that have been labeled severity/irreparability of loss and blame/unfairness. The IEQ has been shown to be internally reliable (Sullivan et al. 2008).

The IEQ total score is measured by summing responses to all 12 items.

Brief Illness Perception Questionnaire (B-IPQ) was used to assess illness perception. The B-IPQ is a very commonly used tool to assess the subject's perception of their illness. In total it consists of 9 items which are scored on a 0-10 scale apart from the final item which is an open-ended question.

Anterior Cruciate Ligament - Return to Sport after Injury (ACL-RSI) questionnaire was used to assess willingness and ability to return to play. The ACl-RSI scale focuses on three main psychosocial areas, emotions, confidence and risk appraisal, that can affect willingness and ability to return to sport safely. The scale has high internal consistency, Cronbach's alpha 0.96 and inter-item correlations were high with a mean of 0.69 (min 0.49, max 0.83) (Webster et al. 2008). The ACL-RSI consists of a unidimensional 12-question scale that measures the three psychosocial domains mentioned above, 5 questions focus on emotions, 5 on confidence in performance and 2 on risk appraisal. The questions are answered on a scale from 0 to 100 in 10-point increments and the total score is represented by the mean total of the answers' given (Webster et al. 2008).

Tegner Activity Scale (TAS) was used to assess the activity level. Activity level and level of sports participation of athletes recovering from ACL is most often measured by self-report and the Tegner Activity Scale (TAS) or by a combination of the above (Neeb et al. 1997). The TAS is a grades activity based on work and sport activities. The TAS consists of a numerical scale (0-10) followed by a sentence describing each level of activity. The subjects is asked to choose the number that best describes their activity level. A higher score indicates a higher activity level. Test retest validity has been found to be acceptable (ICC> 0.70) and internal validity was measured to be a=0.72 (Cronbach). Specifically, the TAS has been tested in the ACL population and seems to demonstrate acceptable psychometric parameters (Briggs et al. 2009).

Knee injury and Osteoarthritis Outcome Score (KOOS) was used to assess knee functional level. It is a knee specific measuring instrument which was originally developed in order to evaluate both the short-term and long-term consequences of a knee injury. The KOOS questionnaire consists of five subgroups referring to pain, symptoms, activities of daily living, sports and recreation functionality and quality of life. In total there are 42 questions and It has been validated on the anterior cruciate ligament reconstruction population and is considered most appropriate for this study since it assesses sport and recreation functionality (Roos and Lohmander 2003).