Physiotherapy assessments traditionally rely on the clinician’s interpretation to evaluate musculoskeletal conditions. However, technology, such as Inertial Measurement Units (IMU), is increasingly used to assist medical professionals. This study evaluates the accuracy and reliability of the Euleria Lab (ELAB) rehabilitation system against an optical motion capture system (OPTO). 7 healthy volunteers were instrumented with 5 IMU and 22 retroreflective markers and performed lower limbs single-plane and multi-plane movements. Joint angles were used to compute Range of Motion (ROM), Root Mean Squared Error (RMSE), Bland-Altman plots and intraclass correlation coefficient (ICC). ROM and RMSE were analysed using two RM ANOVA. In multi-plane tasks, ankle, knee and hip angles were compared using Hotelling’s T2 statistical parametric mapping (SPM) test. No significant differences were found between the two systems for ROM and between tasks in terms of RMSE. However, hip rotation showed large RMSE and poor ICC reliability. Hip flexion and abduction showed good agreement and a systematic bias = 10°. Multi-joint tasks revealed significant differences only in hip flexion during lunges. Therefore, ELAB proved highly accurate and reliable for the assessment of the movements: ankle, knee, and trunk flexion, but demonstrated poor accuracy and agreement during the hip rotation movement. ELAB displayed significant biases but good agreement and minor errors during hip flexion and abduction.