Blood Cell Ratios as Predictors of Response to Platelet-Rich Plasma in Knee Osteoarthritis

Intra-articular platelet-rich plasma (PRP) injection is a widely used treatment for knee osteoarthritis, but patients respond to it very differently and there is currently no simple, inexpensive way to predict who will benefit. The neutrophil-to-lymphocyte ratio (NLR) and related indices derived from a routine complete blood count reflect a person's baseline inflammatory state. This prospective single-arm observational cohort study investigates whether the baseline NLR, together with the platelet-to-lymphocyte ratio (PLR), the systemic immune-inflammation index (SII), and the monocyte-to-lymphocyte ratio (MLR), predicts the clinical response to intra-articular PRP in patients with Kellgren-Lawrence grade 2 to 3 knee osteoarthritis. The investigators will enroll 120 patients aged 40 to 60 years, each of whom receives a standardized course of three leukocyte-poor PRP injections one week apart. Patients are followed for 6 months, and the primary clinical outcome is the change in the WOMAC osteoarthritis index at 6 months. Outcome assessors are blinded to patients' blood-count values. If a baseline blood ratio predicts response, it could become a low-cost tool to guide patient selection for PRP.