Platelet-rich plasma injections in and around the knee for knee osteoarthritis

Osteoarthritis is a degenerative joint disease characterized by progressive cartilage erosion, osteophyte formation, and subchondral sclerosis, leading to pain, stiffness, and functional disability. It is the most common form of arthritis and a leading cause of disability worldwide, affecting approximately 300 million individuals. Although the knee is the most frequently involved joint, OA is now recognized as a whole-joint disease, involving not only cartilage degeneration but also pathological changes in subchondral bone, synovium, and surrounding extra-articular structures.

Platelet-rich plasma is an autologous concentration of platelets suspended in a small volume of plasma and contains a variety of bioactive growth factors, such as transforming growth factor-beta (TGF-β), platelet-derived growth factor (PDGF), and vascular endothelial growth factor (VEGF). These factors play a crucial role in promoting cell proliferation, angiogenesis, and tissue repair. In knee OA, PRP has been shown to reduce matrix metalloproteinase (MMP) activity, particularly MMP-13, enhance endogenous hyaluronic acid production, and support chondrogenesis. Although intra-articular PRP injections are widely accepted as a safe and effective treatment and have demonstrated superiority over placebo and hyaluronic acid in long-term follow-up studies, most existing research has focused exclusively on intra-articular applications.

Knee OA is a multifactorial condition frequently associated with extra-articular pathologies, including ligament laxity, peri-articular edema, and soft tissue inflammation. Limiting treatment to the intra-articular space alone may therefore overlook these important contributors to pain and functional impairment. Emerging evidence suggests that a combined treatment approach targeting both intra-articular and peri-articular structures may provide superior outcomes in terms of pain reduction and functional improvement.

This prospective randomized controlled trial will include 42 patients aged 40-65 years with chronic knee OA classified as Kellgren-Lawrence grade 2 or 3. Participants will be randomly assigned to one of three groups: a control group receiving conservative treatment only (exercise therapy and lifestyle modifications), a group receiving conservative treatment plus ultrasound-guided intra-articular PRP injections, and a third group receiving conservative treatment plus combined ultrasound-guided intra-articular and peri-articular PRP injections targeting the MCL and pes anserinus regions.

Clinical outcomes will be assessed using validated instruments, including the Visual Analog Scale (VAS), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the Short Form-36 (SF-36) Quality of Life Scale. In addition, ultrasonographic measurements of MCL thickness and distal femoral cartilage thickness will be performed to evaluate structural changes. By investigating the additional value of peri-articular PRP injections, this study aims to contribute to the development of more comprehensive and effective injection protocols for the management of chronic knee osteoarthritis.