The assessment of work-related activities and limitations in knee disorders.

The success of knee treatment programs and surgery must be assessed, in part, by both the ability to return patients to work and the documentation of any work-related limitations. Existing occupational rating scales do not rate, in a valid manner, the effect of altered knee function on work activities. We performed a prospective randomized clinical trial in which two different occupational rating systems were tested on 50 patients. One system used job titles and an arbitrary numeric scale for rating occupations; the other used specific criteria for rating job functions according to the intensity, frequency, and duration of certain tasks. The results showed that an effective and valid rating format should consist of five specific objectives: 1) evaluation of different knee functions that typically occur in the work environment; 2) evaluation of work activities separately from sports activities; 3) detection of patients who may have remained at an occupation but who have significantly modified work activities because of knee symptoms; 4) identification of patients who continue to work despite experiencing moderate to severe symptoms; and 5) identification of patients whose work activities decrease because of nonknee-related factors. Furthermore, the results showed that an effective rating system should identify common data reduction errors that can bias the results in analyzing knee-related occupational limitations. The rating system developed circumvents the bias introduced by these anomalies. This system, if adopted by other researchers, would allow for the comparison of treatment results among studies.