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.