Kinesiophobia is Strongly Associated with Altered Loading after an ACL Reconstruction: Implications for Re-injury Risk

OBJECTIVES: The effect of kinesiophobia (fear of movement) following an anterior cruciate ligament (ACL) reconstruction has recently received greater attention. Elevated kinesiophobia as measured on the Tampa Scale of Kinesiophobia (TSK) has been previously found to be associated with poorer outcomes. However, the effect of kinesiophobia in ACL reconstructed patients on high impact and challenging tasks associated with re injury risk such as jumping has not been investigated. Establishing the relationship between kinesiophobia and jump landing mechanics could result in the development of specific treatments to reduce fear of movement and improve jump landing mechanics after ACL reconstruction, resulting in a diminished re-injury risk. Therefore, the purpose of this study is to define the relationship between landing mechanics (axial loading rates and impact forces) with the TSK score in patients 6 months after ACL reconstruction. METHODS: Twenty subjects, 6 months post ACL reconstruction, who had completed post-operative physical therapy, and were cleared by their physician to begin return to sport drills participated in the study. Subjects completed an instrumented drop vertical landing assessment with the ground reaction forces recorded while the subjects performed a drop vertical jump task off a 30.48 cm high box. Three trials were taken and the data were analyzed using custom Labview code and Visual 3D software during the period of time from foot contact until initial impact peak. The average loading rate was defined as the linear portion of the vertical ground reaction curve between 20-80% of foot contact to initial impact peak. Subjects also completed the TSK questionnaire. Associations between loading rate and vertical impact peak to the TSK scale were made with Pearson correlation coefficients with significant relationships defined as p<0.05. RESULTS: 20 subjects (11 female, 9 male, Ages 19 ± 3.3 yrs, H 1.73 ± 0.11 m, M 69.1 ± 12.2 kg) with bone patellar bone autografts completed the study. The mean loading rate was 56.96 ± 18.6 %bodyweight/sec, initial impact peak 0.88 ± 0.24 %bodyweight, and TSK value was 33.1 ± 6.8. There was a significant negative association between poorer responses on the TSK scale and initial impact peak forces (r=-0.624, p=0.003) but not average loading rate (r=-0.243, p=-0.302) (Figure 1). CONCLUSION: We found greater kinesiophobia to be associated with a lower weight-bearing in the ACL reconstructed limb. Potentially, subjects who are afraid of loading their reconstructed limb transfer weight to the uninjured limb, increasing the demand placed upon that limb. The greater forces that the contra lateral limb must absorb may in part be related to the elevated risk of injury associated with the non injured limb. The lack of relationship to loading rate suggests kinesiophobia is more related to the magnitude of the load and not the subject’s ability to control the load. These results suggest that in patients with elevated kinesiophobia, cognitive training may be needed before initiating movement retraining or other exercises to improve landing mechanics. Additional prospective studies are needed to assess if these relationships improve over time and determine the optimal time to intervene to reduce subsequent injury risk.