We conducted a retrospective study to identify the preoperative variables that correlated with a successful outcome for knee arthroscopy in patients over the age of 50. We mailed questionnaires to 94 patients (57 responded) and reviewed their medical records and radiographs. A modified Hospital for Special Surgery knee rating system was devised. The average follow-up was 33 months. The percentage of those who felt they had successful results decreased with time: 82.8% felt their knees had improved immediately after postoperative rehabilitation; this decreased to 78.1% at 6 months, 73.5% at 1 year, 65.5% at 2 years, and 50.0% at 3 years. Therefore, the subjective success rate was 67%. We performed statistical analysis of all variables to determine which had a beneficial or detrimental effect on outcome. In addition, we devised an equation to allow postoperative prediction of score. We found that age was not a factor and that radiographic findings had the greatest impact on postoperative results.