Introduction/Background: Osteoarthritis is a degenerative joint disease that commonly occurs in the elderly population. Treatment goals include pain relief, improvement in knee function, improved quality of life and reduction in disability. Several studies describe the use of biological therapies such as autosomal plateletrich plasma as effective and safe methods in the treatment of pain and joint dysfunction caused by knee osteoarthritis.

Objectives: To evaluate the analgesic, mobility functional improvement efficacy, and safety of intraarticular autosomal platelet-rich plasma (PRP) injection in the primary knee osteoarthritis treatment.

Materials and Methods: Prospective descriptive study of 38 knee joints of 31 patients was diagnosed with primary osteoarthritis according to the American College of Rheumatology (ACR) classification criteria and in Kellgen & Lawrence grade II, III. The patient was assessed about clinical features, subclinical features and the VAS score, Lequesne index at the initial of the study and 30 days later.

Results: The VAS score at 30 days postinjection of PRP lower than the initial value with a statistically significant difference (40.55 ± 9.65 and 65.71 ± 10.06, respectively, with p < 0.001). The Lequesne index at 30 days post-injection of PRP lower than the initial value with a statistically significant difference (12.50 ± 2.64 and 16.74 ± 2.40, respectively, with p < 0.001). The improvement of VAS score and Lequesne index is better in the patient with Kellgren & Lawrence grade II than those with Kellgren & Lawrence grade III (27.24 ± 6.55 and 22.59 ± 5.95, respectively, with p < 0.05). The incidence of the observed complications was not reported in this study.

Conclusions: The intraarticular PRP injection in the primary knee osteoarthritis treatment is a safe approaching and has a significant effect on pain relief and physical function improving after 30 days. The improvement of the VAS score and Lequesne index is greater in the patient with the early grade on Kellgren & Lawrence classification.