Longitudinal assessment of knee joint proprioception using weight-bearing and non-weight-bearing tests throughout rehabilitation after anterior cruciate ligament reconstruction

Objective

Evaluate active knee joint position sense (JPS) throughout rehabilitation after anterior cruciate ligament reconstruction (ACLR).

Design

Longitudinal.

Setting

Motion laboratory.

Participants

Twenty-two individuals post-ACLR and 22 activity-matched non-injured controls performed weight-bearing and non-weight-bearing knee JPS tests. The ACLR participants performed at three functional timepoints: T1, able to perform single-leg sit-to-stand; T2, able to hop maximally; T3, cleared for return to sports. Controls performed on one occasion.

Main outcome measures

Constant, absolute, variable errors (CE, AE, VE) and interlimb symmetry estimates (100% signifying perfect symmetry), for 40° and 65° knee flexion target angles.

Results

For the weight-bearing 40° condition, CE and AE of the ACLR knee significantly increased from T1 to T2 (P = 0.010) and T1 to T3 (P = 0.002). Consequently, interlimb asymmetry for AE significantly increased from T1 (AE_sym% = 101.2% ± 55.4%) to T3 (AE_sym% = 139.7% ± 54.8%). Compared to controls, AE for the ACLR knee was significantly smaller at T1 (P = 0.016). No other significant differences were observed.

Conclusions

Smaller JPS errors at early rehabilitation while weight-bearing may have been due to heightened quadriceps activation and increased γ motor neuron sensitivity, compensating for deficient ACL mechanoreceptors. In contrast, non-weight-bearing testing did not reveal changes over time. Clinicians are advised to consider these distinctions when assessing proprioception at different rehabilitation stages.