Sustained-Release Intra-Articular Drug Delivery: PLGA Systems in Clinical Context and Evolving Strategies

Poly(lactic-co-glycolic acid) (PLGA) sustained-release systems for intra-articular (IA) delivery aim to extend joint residence time and reduce the reinjection frequency of conventional IA therapies. This review synthesizes current understanding of PLGA degradation, the acidic microenvironment inside degrading microspheres, and release behavior in joints, and surveys clinical experience with extended-release corticosteroid depots alongside emerging platforms for nonsteroidal and biologic agents. To situate PLGA within the broader IA field, we briefly summarize selected non-PLGA sustained-release approaches—such as multivesicular liposomes, hyaluronic acid conjugates, and hybrid matrices—to contextualize comparative performance and safety. For proteins and peptides, central barriers include acidification inside degrading microspheres, aggregation during fabrication and storage, and incomplete or delayed release, as illustrated by glucagon-like peptide-1 analog formulations. Mitigation strategies span pH buffering, excipient-based stabilization, and gentler manufacturing that improve encapsulation efficiency and preserve bioactivity. Translation hinges on manufacturing scale-up and quality systems that maintain critical particle attributes and enable informative in vitro–in vivo interpretation. Clinically, prolonged symptom relief after single dosing has been demonstrated for corticosteroid depots (e.g., ~50% pain reduction over 12 weeks with a single PLGA–triamcinolone injection), whereas repeat-dose safety and indication expansion beyond the knee remain active needs best addressed through multicenter trials incorporating imaging and patient-reported outcomes. Consistent real-world performance will depend on controlling batch-to-batch variability and implementing pharmacovigilance approaches suited to long dosing intervals, enabling broader clinical adoption.