Introduction:
Quadriceps lag, an inability to fully extend the knee actively, is a common issue following anterior cruciate ligament reconstruction (ACLR) surgery, often leading to prolonged rehabilitation and suboptimal recovery. This pilot study aimed to assess the effectiveness of incorporating a real-time visual biofeedback device into rehabilitation programs to improve quadriceps lag in ACLR patients.

Subjects and Methods:
In this non-randomised, controlled pilot trial, twelve participants (mean age = 31.3 ± 6.4 years; 7 males, 5 females) with quadriceps lag post-ACLR were assigned to an experimental group (n = 6) receiving biofeedback, and a control group (n = 6) undergoing standard rehabilitation. The experimental group performed 10 repetitions per set, 3 sets per session, daily for 2 weeks. The control group received range of motion and strengthening exercises. Quadriceps lag was assessed using a real-time biofeedback device on days 1 and 10. Statistical analysis included the Shapiro–Wilk test for normality, Levene’s test for homoscedasticity, Wilcoxon Signed-Ranks for within-group comparisons, and Mann–Whitney U for between-group comparisons (p < 0.05).

Results:
The biofeedback group’s quadriceps lag decreased from 15.5° (SD = 2.8) to 1.83° (SD = 1.3); the control group decreased from 14.5° (SD = 1.3) to 6.0° (SD = 1.8). The improvement in the biofeedback group was significantly larger (p = 0.043), with large effect sizes (3.67 experimental, 3.19 control).

Conclusions:
Real-time biofeedback significantly reduces quadriceps lag in ACLR patients. Further research with larger samples is needed. Integrating biofeedback into ACLR protocols could aid clinicians in monitoring and reducing quadriceps lag.