Joint mobilization forces and therapist reliability in subjects with knee osteoarthritis

Abstract

Objectives:

This study determined biomechanical force parameters and reliability among clinicians performing knee joint mobilizations.

Methods:

Sixteen subjects with knee osteoarthritis and six therapists participated in the study. Forces were recorded using a capacitive-based pressure mat for three techniques at two grades of mobilization, each with two trials of 15 seconds. Dosage (force–time integral), amplitude, and frequency were also calculated. Analysis of variance was used to analyze grade differences, intraclass correlation coefficients determined reliability, and correlations assessed force associations with subject and rater variables.

Results:

Grade IV mobilizations produced higher mean forces (P<0·001) and higher dosage (P<0·001), while grade III produced higher maximum forces (P = 0·001). Grade III forces (Newtons) by technique (mean, maximum) were: extension 48, 81; flexion 41, 68; and medial glide 21, 34. Grade IV forces (Newtons) by technique (mean, maximum) were: extension 58, 78; flexion 44, 60; and medial glide 22, 30. Frequency (Hertz) ranged between 0·9–1·1 (grade III) and 1·4–1·6 (grade IV). Intra-clinician reliability was excellent (>0·90). Inter-clinician reliability was moderate for force and dosage, and poor for amplitude and frequency.

Discussion:

Force measurements were consistent with previously reported ranges and clinical constructs. Grade III and grade IV mobilizations can be distinguished from each other with differences for force and frequency being small, and dosage and amplitude being large. Intra-clinician reliability was excellent for all biomechanical parameters and inter-clinician reliability for dosage, the main variable of clinical interest, was moderate. This study quantified the applied forces among multiple clinicians, which may help determine optimal dosage and standardize care.

Keywords:

• Manipulation
• Musculoskeletal
• Physical therapy
• Knee joint
• Osteoarthritis
• Biomechanics

The authors would like to acknowledge Dr Gail Deyle, Dr Kevin Harris, Dr Michael Crowell, and Dr Alden Taylor for their assistance in this study; Dr Seth O’Brien for radiological interpretation of knee radiographs; and Ms Maria Pasquale of Novel Electronics USA for her technical assistance.

The opinions and content of this paper reflect the authors’ opinions and work and do not reflect the official policy or position of the United States Army, the Department of Defense, or the United States Government.