Assessing both physical and mental health is necessary in clinical settings to quantify the scope of disability and to evaluate the effectiveness of treatment programs. Changes in health-related quality of life following physical therapy treatment for many patients with orthopaedic-related diagnoses is not known. The purposes of this study were to describe changes in health-related quality of life between the initial assessment and the time of discharge from physical therapy for the most common orthopaedic diagnoses and to compare the patterns of deficit among diagnostic categories. Patient outcomes in this study were evaluated from a large database generated by the Focus on Therapeutic Outcomes (FOTO) network. Health-related and employment outcomes were described for adult patients who were classified using ICD-9-CM codes. The most common orthopaedic diagnostic categories were sacroiliac sprain, back sprain, low back pain (radiating and nonradiating), neck sprain, neck pain (radiating and nonradiating), adhesive capsulitis of the shoulder, rotator cuff injury, shoulder sprain, knee dislocation, knee sprain, and knee derangement. The primary outcome measure was a 17-item questionnaire (the MOS-17) derived from the RAND 36-Item Health Survey (SF-36) and the 12-item Short Form Health Survey (SF-12). The comparison of each cohort to population norms was made by calculating a standard score on patient data adjusted for age and gender. An effect size was calculated to measure the change in health or employment status between the initial assessment and discharge from physical therapy. For all diagnostic categories, health-related quality of life with respect to norms and employment status showed a consistent pattern of improvement at the time of discharge compared with the initial assessment. There were only small changes in physical function for neck and shoulder diagnostic categories. Nearly all of the diagnostic categories had large reductions in bodily pain. The amount of clinical change in the physical components of health-related quality of life--especially the physical function and role physical domains--differed substantially across specific diagnostic categories. The largest improvements in the physical function occurred for patients with knee dislocation and knee sprain. Patients with knee dislocation also had the largest improvement in role limitations due to physical problems. The design of this study does not permit conclusions about the efficacy of physical therapy. Further study is needed to determine if the finding of different levels of health status improvement across diagnostic categories was due to the nature of the outcome measure, the type of treatments given to each patient, or other confounding variables, like depression or preinjury functional level.