Platelet-rich plasma (PRP) is now one of the most widely used orthobiologics in musculoskeletal medicine, with knee osteoarthritis (KOA) as its main indication. PRP represents a spectrum of autologous preparations with differing cellular and protein content. In this narrative review, we frame current knowledge as a "research ecosystem" spanning mechanistic biology, product characterization, randomized controlled trials (RCTs), systematic reviews and meta-analyses, methodological evaluations, expert consensus, and precision medicine. We highlight the diverse biological roles of PRP components, including the immunomodulatory activity of platelets, the dual regenerative and inflammatory effects of leukocytes, and emerging neutrophil-macrophage crosstalk. Advances in classification systems and deep learning-based quality control are also discussed. Across RCTs, PRP generally outperforms corticosteroids and hyaluronic acid in early to moderate KOA, with benefits lasting several months to a year. Methodological evaluation adds nuance: fragility index analysis confirmed PRP's advantage but showed individual trials were only modestly robust, while spin in systematic reviews often overstated benefits, underscoring the need for more rigorous RCTs and transparent reporting. Leukocyte and platelet concentrations do not explain outcomes, highlighting the importance of patient-specific factors such as metabolic status, inflammation, and structural phenotype. Progress remains hampered by inconsistent reporting, lack of a standardized classification system, and inadequate stratification. We propose a roadmap linking product characterization, standardized reporting, precision patient selection, and objective outcome measures, aiming to shift PRP from a generic injection toward a tailored regenerative therapy.

Thanks to its excellent spatial resolution and dynamic aspect, ultrasound of the shoulder allows an optimal evaluation of tendon, muscle and nerve' structures in shoulder pain. Through this article and owing to inter-observer reproducibility, we will describe an ultrasound standardized protocol (posterior, anterior, global plane) in basic first ultrasounds (ie without tendon abnormality of the supra/infra spinatus, the biceps and subscapularis).

To assess the effectiveness of intra-articular injection of bone marrow concentrate (BMC) under ultrasound (US) guidance in the treatment of patellofemoral osteoarthritis (OA), with clinical and volumetric magnetic resonance (MR) imaging follow-up. This retrospective study included 96 consecutive patients referred for US-guided intra-articular injection of BMC for symptomatic patellofemoral OA for which conservative treatment had failed. A control group of 21 patients with symptomatic patellofemoral OA was included for comparison. Data on International Knee Documentation Committee (IKDC), Visual Analog Scale (VAS), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores as well as volumetric MR imaging (using T2 mapping sequence) were collected before and 12 months after injection, and the results were compared. No technical adverse events were noted during bone marrow aspiration, BMC preparation, or intra-articular injection of BMC. No clinical adverse events were reported during long-term follow-up. All mean scores improved between baseline and 12 months after intra-articular injection of BMC (VAS 5.5 to 3.6, P < .0001; WOMAC 36.8 to 22.2, P < .0001; and IKDC 41.8 to 58.2, P < .0001). MR imaging at 1 year of follow-up after BMC treatment showed no statistically significant difference in hyaline cartilage volume compared with that at the baseline (P = .690), suggesting stabilization of the cartilage degradation process. In contrast, the group of untreated patients showed a significant decrease in the cartilage volume (P = .001), corresponding to a cartilage loss of 6.9%. The results suggest that intra-articular injection of BMC under US guidance could be a promising option for the treatment of symptomatic patellofemoral OA and could promote the preservation of healthy residual cartilage volume.

Background: Iodine contrast agents (ICAs) are routinely used by radiologists to help guide intra‐articular infiltrations. The aim of this study was to assess the in vitro effects of ICA on platelet function of human autologous Platelet‐Rich Plasma (PRP).Methods: One hundred thirty‐seven consecutive patients with symptomatic femoral‐patellar osteoarthritis were included. All were addressed to our institution for a fluoroscopy‐guided intra‐articular PRP infiltration of the pathological femoral‐patellar joint. For each patient, 500 μl of PRP were sampled before intra‐articular injection. First, PRP samples were mixed with 50 μl of 2 widely used ICA: Visipaque270® (Iodixanol, n = 58) and Iopamiron200® (Iopamidol, n = 69). PRP concentration ([PRP]) was measured at different delays of incubation (t = 0, 5, 10, 15, 20 and 30 min) enabling to calculate PRP ratio (defined as [PRP](t)/[PRP](0mn)) at each delay, for each mixture, in order to quantitatively assess the influence of ICA on PRP ratio. Second, the PRP samples of 10 additional patients were mixed with Visipaque270®, Visipaque270®, Iopamiron200® and phosphate buffer saline (PBS: control solution) in order to qualitatively assess the influence of ICA on platelet aggregation, using ADP, Collagen, Arachidonic acid and TRAP tests. The surface expression of human P‐selectin, a marker of α‐granule release, in the PRP + Visipaque270® and PRP + Iopamiron200® mixtures was finally compared. Repeated‐measures ANOVA, classical 2‐way ANOVA and Wilcoxon matched‐pairs test were used to study the influence of ICA on PRP quality.Results: There was no significant change in PRP ratio during the first 30mn of incubation (p = 0.991) whatever the ICA (p = 0.926). Whatever the aggregation test, there was no significant difference in the percentage of platelet aggregation between PRP + PBS, PRP + Visipaque270® and PRP + Iopamiron200® (p = 0.998), nor between PRP + PBS and PRP + Visipaque320® (p = 0.470). Finally, there was no significant difference in P‐selectin expression between the PRP + Visipaque270® and PRP + Iopamiron200® mixtures (p = 0.500).Conclusion: At early delays of incubation, Visipaque® and Iopamiron®, which are two widely used ICA for intra‐articular infiltrations, did not influence the in vitro platelet function nor the quality of PRP.

Objectives: To assess the effectiveness of two consecutive intraarticular injections of PRP to treat knee osteoarthritis (KOA), discriminating between responders and impaired patients. Methods: This retrospective study included 73 consecutive patients who were referred for two intra-articular PRP injections (one week apart) for treating symptomatic moderate/severe KOA. Biological characterization of the PRP, including platelets, leukocytes and erythrocytes, was evaluated. Patient’s subjective symptoms were recorded before the treatment and 1 year after the second injection using pain VAS and WOMAC scores. Responders were defined by an improvement of 10 points on WOMAC. Results: At a 1-year follow up, we found 36 (49.3%) patients who fulfilled the criteria of responders, and 21 (28.8%) patients were impaired. A statistically and clinically significant global improvement of −29.2 ± 14.3 (p < 0.001) points in WOMAC score was observed 1 year after treatment in the responder group, with a higher response rate in patients with KL 2 (57.7%) compared to KL IV (28.6%). The percentage of patients with KL IV was higher in the impaired group (48.0%) compared to the responders (16.6%). As expected, the evaluation of the functionality of the knee in the impaired group indicates that it significantly worsened after one year from treatment (p = 0.027). However, the average pain score remained stable with no significant differences after 1 year (p = 0.843). No clinical complications or severe adverse events after the PRP injections were reported. Conclusion: The present study suggests that two intra-articular injections of 10 mL of very pure PRP provide pain and functional improvement in symptomatic KOA.