Criterion-related validity of knee joint-position-sense measurement using image capture and isokinetic dynamometry

Context: Clinicians require portable, valid, and cost-effective methods to monitor knee joint-position-sense (JPS) ability. Objective: To examine the criterion-related validity of image-capture JPS measures against an isokinetic-dynamometer (IKD) procedure. Design: Random crossover design providing a comparison of knee JPS measures from image capture and IKD procedures. Participants: 10 healthy participants, 5 female, age 28.0 ± 13.29 y, mass 60.3 ± 9.02 kg, height 1.65 ± 0.07 m, and 5 male, 29.6 ± 10.74 y, mass 73.6 ± 5.86 kg, height 1.75 ± 0.07 m. Main Outcome Measures: The dependent variables were absolute error scores (AES) provided by 2 knee directions (flexion and extension). The independent variables were the method (image capture and IKD). Results: There was no significant difference between clinical and IKD AES into knee-flexion data (P = .263, r = 0.55). There was a significant difference between clinical and IKD AES into knee-extension data (P = .016, r = .70). Conclusions: Analysis of photographic images to assess JPS measurements using knee flexion is valid against an IKD positioning method, but JPS measurements using knee extension may not be valid against IKD techniques. However, photo-analysis measurements provided a lower error score using knee-extension data and thus may provide an optimal environment to produce maximal knee JPS acuity. Therefore, clinicians do not need expensive equipment to collect representative JPS ability.