Effects of Immobilization and Re-Mobilization on Knee Joint Arthrokinematic Motion Quality

Abstract

Background: Knee immobilization is a common intervention for patients with traumatic injuries. However, it usually leads to biomechanical/morphological disturbances of articular tissues. These changes may contribute to declining kinetic friction-related quality of arthrokinematics; however, this phenomenon has not been analyzed in vivo and remains unrecognized. Thus, the aim of the present study is to investigate the effect of immobilization and subsequent re-mobilization on the quality of arthrokinematics within the patellofemoral joint, analyzed by vibroarthrography (VAG).

Methods: Thirty-four patients after 6-weeks of knee immobilization and 37 controls were analyzed. The (VAG) signals were collected during knee flexion/extension using an accelerometer. Patients were tested on the first and last day of the 2-week rehabilitation program.

Results: Immobilized knees were characterized by significantly higher values of all VAG parameters when compared to controls (p < 0.001) on the first day. After 2 weeks, the participants in the rehabilitation program that had immobilized knees showed significant improvement in all measurements compared to the baseline condition, p < 0.05. However, patients did not return to normal VAG parameters compared to controls.

Conclusion: Immobilization-related changes within the knee cause impairments of arthrokinematic function reflected in VAG signal patterns. The alterations in joint motion after 6 weeks of immobilization may be partially reversible; however, the 2-week physiotherapy program is not sufficient for full recovery.

Keywords: arthrokinematics; cartilage; crepitus; immobilization; re-mobilization; synovial joint.

Figure 1

The course of representative vibroarthrographic signals for (A) knees after immobilization, (B) knees after rehabilitation (C) control healthy knees. This showcases plots of preprocessed signals, reflecting recorded vibrations expressed in volts with visually defined VMS (variance of the mean squares) and R4 (mean of 4 maximal and 4 minimal values) parameters. Higher signal amplitude means more prominent vibrations.

Figure 2

Spectrograms of the vibroarthrographic signals representative for (A) knees after immobilization, (B) knees after rehabilitation (C) control healthy knees. Short-time Fourier transform analysis serves visual representation of the spectrum of frequencies of a signal as it varies with time. Analyzed frequency bands are marked with lines (P1, power spectral density band of 50 to 250 Hz; P2, power spectral density band of 250 to 450 Hz).