Background: The American Academy of Orthopaedic Surgeons (AAOS) has developed an array of outcomes assessment instruments designed for the efficient collection of outcomes data from patients of all ages with musculoskeletal conditions in all body regions. The Lower Limb Instruments were developed through a process of literature review, consensus-building, and field-testing.

Methods: The instruments were distributed to a total of 290 subjects in twenty orthopaedic practices throughout the United States and Canada. Of the 290 patients, seventy each had a diagnosis in the categories of foot and ankle, sports/knee, and hip and knee and forty each had a diagnosis in the categories of trauma and rehabilitation. Retests to be taken twenty-four hours after the first test were distributed to subsamples of patients for each instrument. Seventy-one one-year follow-up questionnaires (twenty-five Sports/Knee, twenty-five Foot and Ankle, sixteen Hip and Knee, and five Lower Limb Core instruments) were returned.

Results: The Lower Limb Core Scale and the Hip and Knee Core Scale, each consisting of seven items addressing pain, stiffness and swelling, and function, performed at an acceptable level. Additional Sports/Knee and Foot and Ankle Modules proved to have internal and retest reliability of 0.80 or better, comparable with the values for well-established measures such as the Short Form-36 (SF-36). All of the new scales were moderately to strongly correlated with other measures of pain and function, such as physician ratings, the SF-36, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Seventy-one patients provided follow-up information for the analysis of sensitivity to change. The Lower Limb Core was found to contribute independently to the prediction of the transition score based on the patient and physician assessments of change.

Conclusions: The AAOS Lower Limb Instruments for outcomes assessment are highly reliable and are correlated with other measures for similar constructs. They are also sensitive to change in patient status. The Lower Limb Core Scale may be used with attribution of pain either to the lower limb or to a specific joint or side without sacrificing reliability. Combined with the SF-36, the AAOS outcomes assessment instruments comprehensively and efficiently measure outcomes in orthopaedic patients with lower-limb conditions.