Biomolecular condensates as dynamic regulators of musculoskeletal homeostasis, disease, and therapeutic challenges.

Biomolecular condensates are membraneless assemblies that concentrate proteins, nucleic acids, and other biomolecules into dynamic cellular compartments. Liquid-liquid phase separation (LLPS) is one important route by which such condensates form, particularly when multivalent interactions generate liquid-like, reversible assemblies. However, not every condensate or disease-associated assembly should be explained solely by LLPS. In the musculoskeletal system, condensates have been linked to transcription, signal transduction, RNA metabolism, stress responses, tissue development, homeostasis, and mechanoadaptation. Genetic mutations, altered post-translational modifications, and environmental stress can disturb these assemblies, but the evidence does not always establish whether condensates are causal drivers of disease or downstream responses to injury. This review examines how biomolecular condensates and LLPS-related mechanisms have been implicated in osteoporosis, osteoarthritis, skeletal muscle atrophy, bone and soft tissue sarcomas, and neuromusculoskeletal diseases. We focus on the strength of the available evidence, distinguish correlative observations from causal mechanisms where possible, and discuss how condensates may connect non-coding genetic variants, mechanical cues, metabolic signals, and disease phenotypes. We also assess the translational potential and limitations of condensate-based biomarkers, therapies that target pathological condensates, and phase-separation-inspired delivery systems. A central message is that biomolecular condensates offer a useful framework for musculoskeletal biology, but clinical translation will require disease-specific targets, human-relevant models, selective delivery, and rigorous tests of causality.