Biomechanical measures of knee joint mobilization

Background and purpose: The purpose of this study was to quantify the biomechanical properties of specific manual therapy techniques in patients with symptomatic knee osteoarthritis. Methods: Twenty subjects (7 female/13 male, age 54 +/- 8 years, ht 1.7 +/- 0.1 m, wt 94.2 +/- 21.8 kg) participated in this study. One physical therapist delivered joint mobilizations (tibiofemoral extension and flexion; patellofemoral medial- lateral and inferior glide) at two grades (Maitland's grade III and grade IV). A capacitance-based pressure mat was used to capture biomechanical characteristics of force and frequency during 2 trials of 15 second mobilizations. Statistical analysis included intraclass correlation coefficient (ICC3,1) for intrarater reliability and 264 repeated measures analyses of variance and post- hoc comparison tests. Results: Force (Newtons) measurements (mean, max.) for grade III were: extension 45, 74; flexion 39, 61; medial-lateral glide 20, 34; inferior glide 16, 27. Force (Newtons) measurements (mean, max.) for grade IV were: extension 57, 76; flexion 47, 68; medial-lateral glide 23, 36; inferior glide 18, 35. Frequency (Hz) measurements were between 0.9 and 1.2 for grade III, and between 2.1 and 2.4 for grade IV. ICCs were above 0.90 for almost all measures. Discussion and conclusion: Maximum force measures were between the ranges reported for cervical and lumbar mobilization at similar grades. Mean force measures were greater at grade IV than III. Oscillation frequency and peak-to- peak amplitude measures were consistent with the grade performed (i.e. greater frequency at grade IV, greater peak-to-peak amplitude at grade III). Intrarater reliability for force, peak-topeak amplitude and oscillation frequency for knee joint mobilizations was excellent.