Validity and Reliability of the Monitored Rehabilitation Functional Squat Proprioception Test Component

Context: Assessing and restoring proprioception are important aspects of rehabilitation programs. The Monitored Rehabilitation Functional Squat System (MRFSS, Haarlem , The Netherlands) may be a simple and time-efficient means for clinicians to objectively assess joint reposition sense (JRS) during a functional task but its validity and reliability have not been studied. Objectives: To assess the measurement accuracy of the MRFSS and determine validity and reliability of the MRFSS proprioception test component. Design: Single group repeated measures. Setting: Outpatient physical therapy clinic. Participants: Convenience sample of 14 subjects (5 males, 9 females, age=25.6±2.1 yr, height=170.5±10.8 cm, mass=67.6±17.0 kg) with no back, lower extremity, nervous, or uncorrected visual conditions.  Interventions: Prior to subject enrollment, the accuracy of MRFSS measurement of sled travel (500 mm) was compared with actual position measured by tape measure twice per day over 10 days. To study the proprioception test component, subjects completed a single-leg squat on a leg-press-like device interfaced with a computer providing real-time visual feedback of sled position (MRFSS).  After providing consent, the subject’s knee was fit with an electrogoniometer (Biopac Systems, Inc, Santa Barbara , CA ) to determine whether the MRFSS sled position is a valid indicator of knee position during the proprioception test. Then, subjects completed five 60-second trials of a single-leg squat JRS activity involving knee flexion and extension with a resistance of approximately 25% of body mass. The goal was to vary squat position in response to a computer-generated line representing sled/joint position first using visual feedback then attempt to reposition the joint at the same angle without visual feedback. Main Outcome Measures:  A t-test was used to compare the mean sled position from the MRFSS to tape measure to assess the MRFSS’ measurement accuracy. To establish validity of the proprioception test, we used a recognized valid tool, an electrogoniometer. Knee angle data from the electrogoniometer were correlated with millimeters of sled travel using Pearson correlation. Test-retest reliability (ICC(2,1)) was assessed between trials 4 and 5 using normalized performance accuracy ((measured value / target value)*100) for both sled position and knee angle.  Results: MRFSS measurement of sled travel (499.8±1.2 mm) was not different compared to tape measurement (500±0mm, P=0.35). During the JRS task with visual feedback, sled travel and knee angle were strongly correlated (r>-.9, P<0.001); the test-retest reliability was strong for knee angle (r₁₃=.79), and was moderate for sled travel (r₁₃=.65). Conclusion: The MRFSS device provides accurate measurement of sled travel and the proprioceptive test component provides a valid and reliable measure of JRS in this sample of healthy adults. Therefore, the MRFSS may provide clinicians with an objective tool to assess joint proprioception in the clinical setting.

Gattie ER^*, Decoster LC†, Heon MM‡, LaRoche DP§: †NH Musculoskeletal Institute, Manchester , NH ; * Concord Hospital , Concord , NH ; ‡Back in Motion PT, Gorham , ME; § University of New Hampshire , Durham , NH