The reproducibility of multi-joint isokinetic and isometric assessments in a healthy and patient population.

DESIGN: Test re-test reliability design.
OBJECTIVE: To determine a reproducible protocol for lower limb simultaneous multi-joint assessments on a healthy group of subjects and a patient group with patellofemoral pain syndrome.
BACKGROUND: Although single joint assessment with isokinetic dynamometers has been utilised for many years in knee rehabilitation, simultaneous multi-joint assessment has not attracted comparable attention.
METHODS: Twenty healthy volunteers mean age 30.6 years and 16 patients with patellofemoral pain syndrome mean age 29.6 years performed isometric maximum voluntary contractions and concentric isokinetic contractions of the lower limb. Data were collected on three separate days for resultant extension/flexion peak torque, average power and total work which were analysed using intraclass correlation coefficients with a 95% level of confidence.
RESULTS: In healthy subjects, intraclass correlation coefficients estimates were > or =0.75 for isokinetic peak torque and >0.83 for average power and total work. The intraclass correlation coefficients estimate for isometric peak torque extension was 0.82. In the patient group, intraclass correlation coefficients estimates were >0.82 for isokinetic peak torque and > or =0.75 for average power and total work. The intraclass correlation coefficients estimate for isometric peak torque extension was 0.89. Discarding the first session's data for both groups improved the intraclass correlation coefficients estimates for virtually all assessments.
CONCLUSIONS: This study has demonstrated high reproducibility of lower limb multi-joint testing for peak torque, average power, and total work on healthy subjects and then has employed the protocol to demonstrate similarly high reliability on a patient group. It has also highlighted the need for a practice session before the data can be said to be reliable. RELEVANCE: Reliability studies often use healthy subject groups, which although useful, have limited relevance to patient populations. This study has not only gained comprehensive reproducibility data on multi-joint assessment in healthy subjects, it has also shown that multi-joint testing can be used safely and reliably in patients with patellofemoral pain syndrome. Clinicians may now be able to measure objectively lower limb function in this patient group both pre and post treatment.