Optimal Injection Volume in Treatment of Tendinopathy
Authors: Kator Jamie , Mehta Yash , Fu Yunting , Leong Natalie , Gilotra Mohit , Amin Idris 
Published: February 2023

Background: Tendinopathy, a pathology of tendons characterized by inflammation and or degeneration, is a prevalent cause of disease and disability in active and working patients. Within the past decade, orthobiologic injections such as Platelet Rich Plasma (PRP) have become increasingly popular within the musculoskeletal physician’s practice for treatment of chronic tendinopathies. However, there is a lack of standardization of PRP preparation and injection protocols, leading to gaps in our knowledge regarding the optimal administration dosages to maximize treatment efficacy.
Purpose: This review aims to compile and evaluate the existing data for PRP injection volumes for various tendinopathies in hopes of contributing to standardization of PRP protocols, with a further goal of minimiz-ing waste of a costly therapeutic.
Study Design: Systematic Review
Methods: In June 2020, comprehensive electronic database searches were conducted by a medical librarian in Medline via PubMed, EMBASE (embase.com), CINAHL (EbscoHost), CENTRAL and Scopus according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Data was extracted from studies meeting inclusion criteria on injection volumes and outcomes and grouped based on anatomic injection location.
Results: Twenty-eight studies were identified for inclusion in which ultrasound-guided intra-tendinous PRP injections were administered to patients to treat various tendinopathies. For all tendon locations, the mini-mum volume of injectate reported achieved positive clinical outcomes in patients compared to baseline. Conclusions: Despite its many benefits—tendon healing, pain relief, increased function—PRP can pose a significant financial burden to patients, with patients often having to pay for the full cost out-of-pocket due to lack of insurance coverage. This study provides evidence that PRP can be effective at smaller volumes, minimizing waste and the out-of-pocket cost to the patient. In addition, this study further stresses the impor-tance of protocol standardization.
Clinical Relevance: Though more data is needed, it is apparent that the minimum amount of injectate used clinically for various anatomic locations is enough for overall positive outcomes, and therefore can be the recommended dose given. As such, the authors have incorporated the minimum injection volume into their practice using the following volumes: Rotator Cuff-1 mL, Lateral or Medial Epicondyle-1.5 mL, Gluteal or Hamstring-3 mL, Patella-2 mL, Achilles-3 mL. Unfortunately, without more data available in the literature, the authors cannot make stronger recommendations at this time.
What is known about the subject: Among intralesional injections for the treatment of tendinopathy, PRP has shown positive results in multiple trials and has made its way into many musculoskeletal physicians’ practice. However, there is a significant lack of standardization in PRP protocols.
What this study adds to existing knowledge: While other reviews have highlighted the discrepancies amongst PRP protocols, our review is the first to examine injection volume and its effect on outcomes. We were able to suggest a minimum injectate amount for positive outcomes, either pain relief or improvement in the tendon appearance on imaging.