Musculoskeletal disorders are the leading cause of sick leave. Because of the importance of back pain and knee osteoarthritis (ICD-10 diagnoses M54 and M17), these conditions are considered in detail. The aim of this study was to clarify whether job-specific differences in the incidence of sick leave events due to these disorders vary depending on age. The study was based on a secondary analysis of data on sick leave from almost all statutory health insurances in 2008. The database contains aggregated data on sick leave of approximately 26.2 million insured employees. The occurrence of sick leave events resulting from the M54 and M17 diagnoses was defined as the outcome variable. The assignment of employees to occupational groups (Blossfeld classification) was considered as the exposure variable. We calculated the morbidity ratios (SMR) of sick leave occurrence stratified by sex and age. The risk of sick leave was increased for both genders and for both diagnoses, particularly in the occupational groups of the production and service industries with low and medium skill level, even after stratification according to age. Sick leave due to these disorders is a significant issue in these occupations regardless of age, and must be considered with regard to social and preventive aspects.