This is a prospective, observational cohort study involving 40 patients with primary knee osteoarthritis hospitalized in a rehabilitation hospital in Cluj-Napoca. All participants will receive intra-articular platelet-rich plasma (PRP) injections. The study aims to analyze PRP composition and inflammatory biomarkers to better understand disease mechanisms and evaluate treatment effectiveness.

The study is designed as an observational, longitudinal, prospective cohort investigation focused on patients with primary degenerative pathology of the knee joint, specifically primary gonarthrosis. The target population includes individuals diagnosed with knee osteoarthritis, while the accessible population consists of patients admitted to the Clinical Rehabilitation Hospital in Cluj-Napoca.

A total of 40 consecutive patients meeting inclusion criteria will be enrolled. Each participant will undergo treatment consisting of an intra-articular injection of platelet-rich plasma (PRP) at the knee level. The consecutive inclusion approach reduces selection bias and reflects routine clinical practice.

A central component of the study is the biological characterization of PRP. The investigators will analyze its composition, particularly focusing on growth factors such as platelet-derived growth factor (PDGF), transforming growth factor beta 1 (TGF-β1), and insulin-like growth factor 1 (IGF-1). This analysis is intended to contribute to the standardization of PRP therapy in knee osteoarthritis.

In parallel, the study will assess systemic inflammatory status by measuring circulating biomarkers, including interleukins (IL-1β, IL-8, IL-18) and tumor necrosis factor alpha (TNF-α). Monitoring these biomarkers allows evaluation of the inflammatory response and provides insight into the biological effects of PRP on the intra-articular environment.

Overall, the study seeks to clarify both the pathophysiological mechanisms underlying knee osteoarthritis and the therapeutic mechanisms of PRP, while also assessing its clinical effectiveness through changes in inflammatory markers.

Inclusion Criteria:

1. Age between 40 and 80 years
2. Diagnosis of unilateral or bilateral gonarthrosis radiological grade 2-3 Kellgren-Lawrence
3. Knee joint pain greater than 4 on the VAS scale
4. History of knee joint pain for at least 6 months
5. Patients who are to receive an inpatient PRP injection

Exclusion Criteria:

1. Diagnosis of secondary gonarthrosis
2. History of inflammatory rheumatological disease or gout
3. History of recent minor (1 month) or major (2 years) trauma to the knee joint
4. History of knee surgery or arthroscopy
5. Infiltrations, physiotherapy or other knee treatments in the last 3 months
6. Diagnosis of neoplasia, hematological or immunological diseases
7. Clinical or biological signs of acute infection
8. Coagulation disorders