Assessment of injury severity is an integral component of the care of the patient with a fracture of the tibial plateau. Devising ways to reliably quantify injury severity, and to make predictive links between injury severity and outcome, however, has been difficult. Assessment of patient-related factors, such as age, functional capabilities, and medical comorbidities, are necessarily subjective, but certain of these factors clearly shape the treatment plan for a patient with a tibial plateau fracture. Clinical examination findings, such as extent of soft tissue injury and mediolateral stability of the knee, also play an important role in determining treatment and predicting outcome. Radiographic classification of tibial plateau fractures also is an important determinant of treatment, but current classification systems have suffered from disappointing interobserver reliability. Although the severity of injury to the articular cartilage almost certainly affects outcome, there currently are no validated modalities to measure this important factor. More carefully validated tools are needed in many of these areas if we are to perfect our understanding of injury severity and establish more accurate correlations between injury severity and outcomes.