Background: The main target of the structural damage in osteoarthritisis the hyaline cartilage. New options such as PRP (platelet rich plasma) may cause structural improvement of the cartilage. Objective: The aim of ourstudywas to evaluate the evolution of the patients with knee osteoarthritis on PRP treatment. Material and method: The patients with osteoarthritis were evaluated at enrolment and every three months by ultrasound knee ecography. A semi-quantitative knee ultrasound score was applied to monitor changes before and after the treatment. The score was composed by the presence of the following: bursitis (1 point), hypoechogenic changes at the level of the hyaline cartilage in the anterior transversal window (1 point), asymmetrical narrowing of the cartilage (1 point), the involvement of the medial cartilage in the longitudinal approach (1 point), the involvement of lateral cartilage in the longitudinal approach (1 point) and the presence of step up lesions – osteophytes (1 point The evaluation was performed independently by two separate physicians. Another ultrasound – trained doctor was analysing all the images. Results: Twenty – nine patients were included in our study; with one patient excluded due to masive bursitis. No differences were found concerning the pathological findings between the first two evaluators (p: 0.1250). So far, only nine patients have been evaluated at three months, and we were unable to find any improvements or worsening concerning the ultrasound alterations (p: 0.0625). The ultrasound lack of modifications was not correlated with the functional status of the subjects. Conclusions: In the short term, the local treatment showed no improvement on structural damage, but it improved the overall status of the patients (less pain, improved mobility, a better quality of life).