A patient’s activity level is increasingly recognized as an important factor that can influence orthopaedic outcomes. Validated, reliable activity measurement tools now exist for the shoulder, hip, knee, and ankle. These tools can be directly applied as outcome measures that determine whether interventions restored function. It is now evident that activity level is a powerful prognostic factor for outcomes in orthopaedic procedures such as anterior cruciate ligament reconstruction, articular cartilage repair, and total joint arthroplasty. Yet despite the recent increase in studies that have made use of quantitative, joint-specific activity scales, much room remains for further understanding of the exact role of activity level in the progression, treatment, and patient perception of musculoskeletal disorders, particularly in the shoulder and ankle, as well as in pediatric patients.