A novel mechanosensitive stress test in individuals following anterior cruciate ligament reconstruction: A pilot study.

OBJECTIVES: 1. Assess serum biomarker responses of the anterior cruciate ligament reconstructed (ACLR) knee compared to the non-injured contralateral knee in a lateral tilt paradigm. 2. Determine the relationship between kinematics at the ACLR knee and serum biomarker responses. METHOD: Cross-sequential study. 16 participants 2-7 years post-ACLR, undertook two 30 ​min walking sessions on a 10° angular tilted treadmill towards the ACLR knee and/or contralateral non-injured knee. Serum collected at baseline and after 30 ​min of walking was tested for biomarkers associated with osteoarthritis (Cartilage oligomeric matrix protein [COMP]), C-terminal cross-linked telopeptides of type II collagen, matrix metalloproteinase-3,-13, ADAM a disintegrin and metalloproteinase with thrombospondin motifs 4-,-5 (ADAMTS-4,-5), interleukin-1β,-6,-8 and RANTES (regulated on activation, normal T-cell expressed and secreted). Kinematic measurements were also taken. RESULTS: When tilted towards the ACLR knee, there was a significant increase in COMP compared to baseline (mean 41.1 ​ng/mL (95%CI:13.8,68.4), not observed when tilted towards the contralateral knee. There was a significant correlation between change in COMP concentration and change in knee adduction/abduction angle (r ​= ​-0.58,p ​= ​0.02). There were no relationships to kinematics and the other biomarkers. CONCLUSIONS: The tilt paradigm identified a differential response of a serum mechanosensitive marker (COMP) when testing an ACLR and contralateral knee. There was also a significant relationship between COMP response to tilt walking and the change in knee adduction angle of the ACLR knee. This paradigm could be an aid to provide individual knee biomarker response to a mechanical stress in asymptomatic individuals at risk of developing post-traumatic osteoarthritis at least 2 years post-ACLR.