The definition of platelet rich plasma (PRP) is still controversial, though it can be described in general terms as ?a volumeof autologous plasma that contains a higher platelet concentration than the physiological basal concentration?. A retrospective observational analytical study was carried out in our hospital in order to assess the results and satisfaction of patients that had undergone PRF injection in knee. Between January and December of 2017, 80 gonoarthrosis patients treated with PRF injection were selected by the Orthopaedic Surgery and Rehabilitation Department, all of whom attended several medical appointments to check their recovery. Those cases that did not follow an appropriate clinical follow-up were dismissed from the study.Pain before treatment was assessed by the Numeric Rating Scale, with a mean of 8.48. A statistically significant decrease was observed after treatment (p<0.001), with a 4.87 mean and a 5.00 post-injection median. Regarding walking perimeter, most patients walked a median of 30 minutes and 55.3 minute mean, and their walking autonomy increased after treatment, doubling the median to 60 minutes, with an average of 93.15 minutes of pain-free walking. This 37.8 minute increase in the walking ability impliesa statistically significant improvement (p<0.001). A significant decrease in analgesics intake after treatment was also observed, being 81.3% patients who needed analgesia prior to treatment (n=61), and just 49.3% (n=37) after the procedure.Consequently,there is a significative improvement of pain, walking perimeter and absolute intake of analgesics that cannot be explained by any variable prior to PRF injection.