BACKGROUND knee osteoarthritis (KOA) is known as the most common form of osteoarthrosis with a 6% prevalence in people over 30 years old, and more than 40% in the population over 70 years old. The use of PRP led to diverse results and this disparity can be attributed to the dissimilar methods of PRP preparation. This study aims to assess the functional effects of intraosseous (IO) and intraarticular (IA) injections of platelet rich plasma (PRP) followed by IA injections of hyaluronic acid (HA). OBJECTIVE this study aimed to assess the functional effects of intraosseous (IO) and intraarticular (IA) injections of platelet rich plasma (PRP) followed by IA injections of hyaluronic acid (HA), administered 3 and 4 weeks after the initiation of treatment in 33 patients with grade II-III (Ahlback scale) knee osteoarthritis (KOA). METHODS retrospectively, 33 patients were assessed using the Western Ontario and McMaster Universities (WOMAC) osteoarthritis index and visual analogue scale (VAS) score. They were followed-up for 12.92 months on average. Patients were divided into three groups based on age and four groups based on the follow-up period. RESULTS the pre-operative mean of the WOMAC index was 44.35 ± 20.20 and the post-operative mean was 22.81 ± 17.25 (p < 0.001). The pre-operative and post-operative mean of the VAS scores were 5.79 ± 2.01 and 2.41 ± 1.43 (p < 0.001), respectively. The largest improvement in WOMAC (from 42.86 to 13.69) was observed in the youngest patients (44 to 55 years old) and the largest reduction in VAS (from 6.89 to 2.22) was seen in patients aged 56 to 70 years. CONCLUSIONS the combination of IO and IA plasma rich in growth factor (PRGF) treatment with the IA-HA treatment yielded excellent results, diminishing pain and improving motor functionality in patients with KOA.