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.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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