Introduction Despite the high prevalence of musculoskeletal diseases, in Spain there are few data about how these conditions affect the quality of life of individuals. The objective of this study was to assess the quality of life (QOL) of patients candidate for orthopedic surgical treatment using an age-gender adjusted method of QOL scores. Materials and methods The SF-36 Health Survey was administered to 538 patients candidate for surgery between surgical treatment was classified in four groups (lumbar disease, cervical disease, knee arthroplasty, and hip arthroplasty). Associated morbidities were collected retrospectively for all cases using the Charlson co-morbidity index. Univariate, bivariate, and multivariate statistical analyses were done to compare the four groups to each other, to the general population mean, and to the age and gender-adjusted population mean. Results 234 men and 304 women whose mean age was 58.78 years (19-89) were assessed. Patients candidate for some kind or lumbar surgery had the worst scores in all physical and mental scales as compared to the other disease groups. Patients candidate for knee arthroplasty, had the best quality of life scores in all scales, compared to the other disease groups. Medical conditions had no influence over the summary measures. Conclusion Presenting the results of SF-36 in standard deviations from the age-and gender-adjusted population mean (T values) leads to a better appreciation of the differences between the various diseases. Patients candidate for surgery of the lumbar spine had a worse QOL, while the QOL in patients candidate for knee arthroplasty was the least affected.