Urinary biomarkers and occupational musculoskeletal disorders in the lower limbs

Background Causation of occupational musculoskeletal disorders of the lower limbs (LLMSDs) may be multifactorial, including abnormal biological processes. Clinically validated biomarkers that reflect degradation of bone, cartilage and synovial tissue may be useful in identifying such processes in those presenting with LLMSD. Aims To investigate two urinary biomarkers as objective measures of occupational LLMSDs. Methods This cross-sectional study involved both working (n = 146) and case cohorts (n = 62); the latter were derived from general practitioner referrals or those occupationally re-deployed due to LLMSDs. Urine measurements of the c-telopeptides of collagens I and II and two validated quantitative questionnaires [ SF12v2 and the Rheumatoid and Arthritis Outcome Score (RAOS) questionnaires] were the outcome measures. Results Urinary collagen II biomarker had largely the same significant discriminant power in distinguishing working from case cohorts, as several item scores within the RAOS questionnaire. Increased perceived pain within the RAOS questionnaire was statistically correlated to higher levels of the collagen II biomarker in all subjects and the combined working cohorts. However, both the pain score and the collagen II biomarker were significant but independent variables in distinguishing cases from non-cases. High levels of current or past sports activity involving the lower limbs were not significant explanatory variables of the collagen II levels. Collagen I biomarker showed no discriminant power between cases and working cohorts, suggesting that increased bone turnover was not a significant feature in the LLMSD cases. Conclusions Urinary c-telopeptide of collagen II showed promise as a non-invasive, objective marker of abnormal biological process in LLMSDs.