Subjective knee apprehension is not associated to physical parameters 6-12 months after anterior cruciate ligament reconstruction

Purpose: Anterior cruciate ligament (ACL) rupture is a common injury and psychological parameters measured at 6-8 months are said to be almost more predictive for return to sport (RTS) than physiological. Purpose was 1) to evaluate the correlation between knee apprehension using ACL-RSI and physical factors after ACL reconstruction (ACLR), 2) to assess the correlation between ACL-RSI and patient parameters (age, pivot-sport, BMI), and 3) to evaluate ACL-RSI over time. Methods: Patients with ACLR with or without meniscal repair between 2013 and 2020 were retrospectively analyzed. Including criteria were RTS testing battery, assessed at least 6 months after surgery, including physical parameters (strength, triple hop test, side hop test, and bilateral knee stability) and psychological parameters (ACL-RSI). 5 subgroups were analyzed to assessed factors such as age, BMI, pivot sport, time interval between two RTS testing battery. Results: Three hundred three patients (212 male, 91 female) presenting ACLR were included. Mean age at surgery was 27 (+/- 8) years. 258 patients practiced pivot-sport activity and 45 non-pivot-sport activity. The mean interval between ACL rupture and surgery was 6.5 (+/- 4.5) months. RTS testing battery were performed at 8 (+/- 7) months after ACLR. Mean ACL-RSI was 58 (+/- 28). 1) ACL-RSI was not influenced by muscle strength, coordination and stability of the knee. 2) ACL-RSI was significantly better in lower BMI and non-pivot-sport activities. No correlation was found between graft type, age, sex, and ACL-RSI assessment. 3) For patients who performed two RTS testing battery at 8 and 12 months, ACL-RSI did not significantly increase over time (56 to 64 points, p= 0.22) in spite of significant increased quadriceps (127 to 151 Nm/kg, p = 0.005) and hamstring (93 to 105 Nm/kg, p = 0.05) strength. Conclusions: Psychological readiness before RTS, measured upon ACL-RSI does not correlate with any physical parameter at 8-12 months postoperatively. Although quadriceps and hamstring strength increased significantly over time, ACL-RSI does not and must therefore be routinely assessed.