Preoperative and Postoperative Kinesiophobia Influences Postoperative Outcome Measures Following Anterior Cruciate Ligament Reconstruction: A Prospective Study

The anterior cruciate ligament (ACL) is the most injured ligament of the knee, and the treatment of choice is usually ACL reconstruction. Kinesiophobia refers to an irrational and paralyzing fear of movement caused by the feeling of being prone to injury or reinjury. The aim of the present study is to evaluate the relationship between preoperative and postoperative kinesiophobia with postoperative outcomes of ACL-R evaluated through SF-36, ACL-RSI, KOOS, and OKS scores. Included patients all underwent ACL reconstruction. The preoperative TSK-13 questionnaire and six-month postoperative TSK-13, ACL-RSI, SF-36, KOOS, and OKS questionnaires were assessed in included patients. Normal distribution was assessed using the Shapiro–Wilk test. The study included 50 patients who filled out the questionnaires at the 6-month postoperative follow-up. Correlations between preoperative TSK-13 and postoperative outcome measures revealed a low–moderate negative correlation between preoperative TSK-13 and SF-36 PCS at 6-month follow-up. Correlations between postoperative TSK-13 and postoperative outcome measures revealed a high negative correlation between preoperative TSK-13 and ACL-RSI, KOOS Symptoms, KOOS Pain, KOOS ADL, and OKS at 6-month follow-up. Preoperative and postoperative kinesiophobia were found to influence postoperative ACL-R outcomes negatively, more specifically an increase in kinesiophobia showed a statistically significant correlation with worse postoperative SF-36 PCS scores in patients.


Introduction
The anterior cruciate ligament (ACL) is considered to be the most injured ligament of the knee, and the treatment of choice when such a condition causes functional instability is usually ACL reconstruction (ACL-R) [1]. A recent population-based study found that the incidence of ACL tears is approximately 68 per 100,000 person-years, making it a common orthopaedic injury; in the US alone, approximately 100,000 reconstructions are performed annually [2][3][4][5]. Furthermore, large registry databases along with several cohort studies have revealed that the incidence of ACL-R is increasing worldwide [1].
In general, musculoskeletal (MSK) conditions such as ACL injury are usually approached using traditional educational models which heavily incorporate the biomechanics, anatomy, and pathoanatomic features of injury [6][7][8]. Such approaches are essential in the medical evaluation of conditions and in determining an appropriate treatment plan; 2 of 11 nonetheless, they fail to incorporate the psychosocial component often associated with MSK disorders [6,9,10]. Chronic musculoskeletal pain (CMP) is defined as an ongoing pain felt in joints, bone, and tissues persisting longer than 3 months, and in Western society impacts about 20% of adults [11]. Widely accepted contributors to this kind of pain and its consequent disability include behaviours such as pain catastrophizing, anxiety, fear during movement, and nervous system sensitization [9,11]. These behaviours are at the basis of the development of kinesiophobia in patients suffering from musculoskeletal disorders such as ACL injury. Kinesiophobia is defined as an irrational and paralyzing fear of movement caused by a feeling of being prone to injury or reinjury, and as mentioned is both influenced by and influences chronic pain conditions and associated behaviours [12][13][14].
Kinesiophobia is evaluated using the Tampa Scale of Kinesiophobia (TSK) [12]. This condition may be a cause as well as a symptom of disability in orthopaedic patients, and bears a strong psychosocial component [12]. It has two main recognized causes including via a direct painful or traumatic experience or via learned social behaviours [12,13]. Its prevalence in patients suffering from persistent pain usually ranges between 50% and 70% and has been shown to alter the biomechanics of movements and the perception of pain [12].
Most recently, studies have shown that biopsychosocial treatment targeting the physical, psychological, and social factors surrounding pain and disability are most effective in the treatment of chronic pain [9,11]. Such findings, as discussed, bring to light the relationship between the psychosocial components of pain, chronic pain conditions, and fear behaviours (including kinesiophobia) and MSK disorders and treatment outcomes. Studying these relationships in practice has the potential to provide lasting change to the approach to treatment in the field of orthopaedics for the benefit of patients. Thus, evaluating these parameters in the context of specific surgical procedures, such as ACL-R, is a step in the right direction. The aim of the present study is to evaluate the relationship between preoperative and postoperative kinesiophobia with postoperative outcomes of ACL-R evaluated through SF-36, ACL-RSI, KOOS, and OKS scores.

Materials and Methods
In total, 50 patients (19 females and 31 males) who underwent ACL-R were included in the present study. All included patients were operated on by the same expert surgeon at our centre over the course of three years and followed the same standardized rehabilitation protocol.
The preoperative TSK-13 questionnaire and six-month postoperative TSK-13, ACL-RSI, SF-36, KOOS, and OKS questionnaires were assessed in included patients. Preoperative questionnaires were administered "in-person" by trained nursing staff on the day of intervention. The same nursing staff administered the postoperative questionnaires in the hospital during the 6-month follow-up visit, or alternatively contacted patients via phone. Nurses received training for the administration of the questionnaires and were available to patients for clarification when necessary. Patients were not made aware of the goal of the study when filling the questionnaires.
Six-month follow-up for administration of postoperative questionnaires allows for a sufficient recovery period from the time of intervention to assess meaningful outcome measures. Furthermore, this timeframe allows for the evaluation of the very first changes in quality of life and function following recovery.

Anterior Cruciate Ligament-Return to Sport after Injury
The ACL-RSI is a questionnaire that evaluates return to sports after injury [18]. It consists of 12 questions, each scored on an 11-point Likert scale from 0 to 100. The total score is determined by summing the scores for each question and expressing them as a percentage, with a range of 0 to 100 indicating the worst and best conditions, respectively.

Short-Form Health Survey-36
The SF-36 questionnaire evaluates general health indicators and generates a corresponding score [19]. It consists of 36 questions divided into eight sections comprising a Physical Component Summary (SF-36 PCS) and a Mental Component Summary (SF-36 MCS), in addition to the inclusion of a single unscaled question regarding health changes in the past year (SF-36 Health Change) [19].

Knee Injury and Osteoarthritis Outcome Score
The KOOS is self-administered questionnaire and contains 42 items sectioned into five subscales: Pain, Symptoms, Activities of Daily Living (ADL), Sport and Recreation (Sport/Rec), and Knee-related Quality of Life (QOL). A five-point Likert scale ranging from 0 (no difficulties) to 4 (severe problems) is used to score each question. The final score is calculated by summing the score obtained for each question.

Oxford Knee Score
The OKS (Oxford Knee Score) is a questionnaire consisting of 12 items that evaluate pain and daily living activities related to the knee. The questionnaire is divided into two subscales for pain and function, each comprising five response categories that are scored on a 1-5 Likert scale. One may obtain a minimum total score of 12 and a maximum total score of 60.

Statistical Analysis
A priori power analysis was performed, with a level of significance of 0.05, a statistical power of 80%, a correlation of −0.48 between TSK and ACL-RSI, and a minimum total sample size amounting to 31 subjects [18].
To evaluate the normal distribution of the data, the Shapiro-Wilk test was employed. As the data did not exhibit a normal distribution, the Independent-Samples Mann-Whitney U Test was used to calculate the variations in scores between the groups (preoperative kinesiophobia versus no preoperative kinesiophobia and postoperative kinesiophobia versus no postoperative kinesiophobia). Additionally, the relationship between preoperative TSK-13 scores and postoperative scores was measured via Spearman's correlation.
SPSS for Windows (version 26; Armonk, NY: IBM Corp), R Core Team (2020) version 4.0.3, and SAS OnDemand for Academics were used to perform all statistical analyses and produce figures.

Results
Overall, 50 eligible patients (19 females and 31 males) were included in the study. All patients completed the questionnaires at the 6-month postoperative follow-up. All included patients are of Italian nationality. The mean age at the time of intervention was 39 in females, 30.1 in males, and 33.6 overall. The oldest included patient was a 63-year-old female and the youngest was a 16-year-old male.
Patients without preoperative kinesiophobia showed higher values of the SF-36 PCS ( Table 2).

Discussion
The results suggest that patients suffering from kinesiophobia preoperatively and postoperatively suffer from worse ACL-R outcomes as measured via the utilized scores. Specifically, a negative correlation was found between an increase in TSK-13 score preoperatively and postoperative SF-36 PCS score, and between an increase in TSK-13 score

Discussion
The results suggest that patients suffering from kinesiophobia preoperatively and postoperatively suffer from worse ACL-R outcomes as measured via the utilized scores. Specifically, a negative correlation was found between an increase in TSK-13 score preoperatively and postoperative SF-36 PCS score, and between an increase in TSK-13 score postoperatively and postoperative ACL-RSI, KOOS Symptoms, KOOS Pain, KOOS ADL, and OKS scores.
A low-moderate negative correlation was identified between preoperative TSK-13 and postoperative SF-36 PCS at the 6-month follow-up. As the TSK-13 score increased in the "kinesiophobia" group, the postoperative SF-36 PCS score decreased. Conversely, patients placed in the "no kinesiophobia" group showed statistically significantly higher SF-36 PCS values postoperatively. The PCS assesses physical function, role limitations caused by physical problems, bodily pain, and general health across four predetermined domains. A lower score on this assessment indicates poorer overall physical health, and in this case, the decline in the SF-36 PCS value appears to be linked to kinesiophobia. Brown et al.'s systematic review evaluated the influence of kinesiophobia on outcomes after total knee arthroplasty (TKA), concluding that its presence negatively impacted functional outcomes for up to a year after surgery [22]. This is consistent with the present findings on ACL-R. Furthermore, research has shown that kinesiophobia can independently predict postsurgical function, even when controlling for other psychological and physical variables [22].
The term kinesiophobia inherently encompasses a multitude of behaviours and attitudes regarding pain and movement, including pain catastrophizing, fear of movement, and possibly associated mood disorders such as anxiety and depression [23]. Such attitudes towards pain have been recognized in some cases as predictors of poor recovery from TKA and several studies show that they may be some of the strongest psychological predictors of return to work following orthopaedic injury [23,24]. The postoperative SF-36 PCS score itself may serve as a tool to measure a patient's ability to return to daily activities, work, and perhaps even sports thanks to its quantitative evaluation of physical well-being. Thus, kinesiophobia experienced before ACL-R may be at play in patients' ability or inability to return to their full physical potential following surgery given its negative effects on surgical outcomes as measured via the SF-36 PCS score.
A high negative correlation was found between postoperative TSK-13 and postoperative outcome measures; in fact, as the preoperative TSK-13 score increased ACL-RSI, KOOS Symptoms, KOOS Pain, KOOS ADL, and OKS values were found to decrease. Furthermore, patients without preoperative kinesiophobia in the first place showed statistically significant higher values for ACL-RSI, KOOS Symptoms, KOOS Pain, KOOS ADL, and OKS.
An evaluation of the occurrence of postoperative fear of movement in TKA and its effects on outcome measures postoperatively found that the OKS score at 6-month followup was significantly lower in patients who suffered from fear of movement [25]. Similarly, in the present study, it was discovered that patients with postoperative kinesiophobia following ACL-R showed lower OKS scores compared to their "no kinesiophobia" counterparts. Although TKA and ACL-R are different surgical procedures in both cases, there seems to be a negative relationship between postoperative kinesiophobia and specific surgical outcomes.
Return to sports after injury, measured via ACL-RSI score, was found to decrease with an increase in kinesiophobia, indicating that patients affected by this condition are less likely to return to physical activity. This score is measured based on three domains-emotions, confidence, and risk appraisal-ultimately evaluating emotional and physiological readiness to return to sports (RTS) following injury and surgical intervention. The extent of self-reported fear in some studies was shown to predict both second injury to ACL and return to sport [26]. Patients who reported higher levels of fear during the RTS phase of recovery were more likely to exhibit reduced activity levels, experience asymmetry during the single leg hop for distance assessment, and have an elevated risk of experiencing a second ACL injury within 24 months [26]. These results are in line with the present findings given that at the base of kinesiophobia is the fear of movement. Another study even found that kinesiophobia negatively affects range of motion (ROM) and that this issue is not resolved by simply demonstrating patients' ROM in theatre [22]. The exclusion of patient-reported fear of movement from discharge planning algorithms following ACL-R is commonplace and its introduction as an evaluating factor and possibly its integration into rehabilitation programs could yield positive outcomes for patients [26]. Rehabilitation programs alone are crucial for the achievement of successful postoperative outcomes and as a result should also tend to the psychosocial components of recovery [27]. Overall, concordant findings stress the need to incorporate strategies to tackle preoperative and postoperative kinesiophobia to promote RTS and return to daily activity following ACL-R.
The results showed that KOOS Symptoms, Pain, and ADL domains were all worsened in patients suffering from postoperative kinesiophobia. It is likely that kinesiophobia and the worsening of these outcome measures have a mutual influence on one another. It has been reported, for example, that negative outcome expectations (to which kinesiophobia often contributes) are detrimental to patient motivation, reducing the likelihood of individuals to initiate the behaviours necessary to resume ADL and sports following certain orthopaedic procedures [23]. Knowing the positive direct and indirect effects that physical activity has on mental health, an increasingly sedentary lifestyle may aggravate an already precarious psychological condition, possibly worsening the kinesiophobia that is already at play in affected patients whilst hindering recovery [28]. Such observations in combination with the present findings further stress the need for consideration and awareness of this condition in the field of orthopaedics, especially in postoperative rehabilitation programs, to, amongst other things, maximize patients' ability to RTS, return to ADL, and allow the achievement of full ROM postoperatively.
A pilot study by Coronado et al. evaluated the role of psychosocial states and behaviours on postsurgical outcomes by trialling a telephone-delivered cognitive-behaviouralbased intervention to be implemented prior to and immediately after ACL-R [3]. It was designed to target a variety of psychological factors including those influencing fear behaviours, which are intrinsic to kinesiophobia [3]. Following this trial, meaningful reductions in fear of movement or reinjury and catastrophizing and an increase in self-efficacy were observed, and authors even reported an increase in KOOS QOL 6 months postoperatively [3]. The combination of conducting further research regarding the influence of kinesiophobia on orthopaedic procedures and the development of introspective therapeutic programs incorporating approaches oriented towards targeting psychosocial factors is a step in the right direction. The development of novel additions to rehabilitation programs perhaps has the potential to be life-changing for many orthopaedic patients by improving postoperative outcomes.

Limitations
The limitations of the present study include the lack of randomization, which inevitably increases the likelihood of confounding factors and bias. Furthermore, the use of patient-reported outcome measures (PROMs) may influence the comparability of results across samples given the introduction of patient subjectivity. To minimize this, data were collected utilizing well-researched surveys, translated professionally into the Italian language, and the questionnaire procedure was carefully explained to the included patients. In addition to this, surveys were performed 6-months postoperatively, allowing a substantial recovery period and making the results more comparable.
In addition to this, more data regarding patient demographics and a subsequent stratification of results may be beneficial in future studies. Stratifying patients by characteristics such as sex and age may provide more information on the influence of kinesiophobia in specific subgroups.
Furthermore, much of the literature referenced regarding the relationships between kinesiophobia and postoperative outcomes regarded TKA instead of ACL-R; such data were utilized nonetheless as a means of comparison in the present study. Regardless, the lack of available literature on the matter highlights the necessity for more research in this field.

Conclusions
Both preoperative and postoperative kinesiophobia were found to influence postoperative ACL-R outcomes negatively. In the case of preoperative kinesiophobia, SF-36 PCS was found to have a negative relationship with increasing kinesiophobia. In postoperative kinesiophobia, a negative relationship was recognized between increasing kinesiophobia and ACL-RSI, SF-36, KOOS, and OKS scores. Psychosocial factors have been continuously shown to influence overall health and the present study attests to that. Patients suffering from this complex cognitive-behavioural condition closely associated with pain and fear were found to suffer from worse ACL-R outcomes, which possibly contributed to a slowed or impeded recovery. Ultimately, more studies are needed regarding the role of psychosocial factors, such as kinesiophobia, on postoperative outcomes in the field of orthopaedic surgery, as well as more effort towards the development of preoperative and postoperative therapeutic and rehabilitation programs that tend to these conditions.