The long term monitoring of the knee angle in asymptomatic participants: a spectrum analysis

Objectives Range of movement (ROM) of clinical groups is routinely measured in a laboratory or clinical setting. It is suggested that due to the Hawthorne effect this may not accurately reflect their ROM over a 24 hour period. The objective of the investigation was to determine if the long term monitoring of the knee angle was logistically possible away from the laboratory environment, and to obtain a normative data set of the knee angle during seven hours of ambulation in asymptomatic participants. Methods Flexible electrogoniometry was used to monitor the right knee flexion angle in the sagittal plane using a portable data logger, configured at a sampling rate of 200Hz. Participants (n = 10) were fitted with the system at a mean of 8.02 am ± 0.03 hours in the laboratory and subsequently asked to return seven hours later with a view to obtaining a representative sample of their normal ROM during an average day, away from clinical observation. Results Mean findings suggested that the largest percentage duration of the seven hour monitoring period was spent between ? 20 - <40° (27.30%) of flexion. There was a mean reduction trend in 10° increments of 1.88% ± 0.91% between the flexion angles of 20° and 110°. Only 0.31% of the monitoring period was spent at a flexion of ? 100°, suggesting few deep knee flexion activities undertaken. The mean velocity spectrum showed that 43.23% ± 1.71% of the monitoring time participants flexed their knee between 0 – 100°/s, with mean extension between 0 - 100°/s calculated at 42.77% ± 2.48%. Conclusions The investigation provides a valid, repeatable, and cost effective method of long term angular monitoring, with the potential for development to examine 24 hour patterns of movement. This system could be used to monitor and compare clinical populations in the outpatient setting.