This 2017 narrative review by Chen et al. surveys OA pathobiology across etiology, animal models, research techniques, and pain mechanisms. Its central argument: OA is a whole-joint organ disease driven by interacting molecular pathways, not isolated cartilage wear. No disease-modifying treatment currently exists — understanding why requires grasping the competing and context-dependent signals reviewed here.
Pain severity in OA frequently does not match radiographic destruction — and this review explains why. The CCL2/CCR2 axis in dorsal root ganglia drives nociceptor excitability independently of cartilage loss, while NGF/TrkA sensitization amplifies pain through TRPV1 and substance P upregulation.
When a patient with mild radiographic OA reports severe pain, or a patient with bone-on-bone changes reports tolerable symptoms, the molecular dissociation between structural damage and pain signaling is the explanation.
This also explains the tanezumab safety signal: NGF promotes angiogenesis and nerve ingrowth into the joint, and systemic inhibition disrupted protective signaling in bone, leading to rapid OA progression and fractures in a subset of patients.
For counseling patients on why no disease-modifying OA treatment exists: TGF-β is protective in cartilage but harmful in subchondral bone, meaning any systemic modulation of a shared pathway risks off-target damage. Single-target systemic therapy is structurally prone to failure in a whole-joint disease with context-dependent signaling.
This 2017 narrative review by Chen et al. surveys OA pathobiology across etiology, animal models, research techniques, and pain mechanisms. Its central argument: OA is a whole-joint organ disease driven by interacting molecular pathways, not isolated cartilage wear. No disease-modifying treatment currently exists — understanding why requires grasping the competing and context-dependent signals reviewed here.
Pain severity in OA frequently does not match radiographic destruction — and this review explains why. The CCL2/CCR2 axis in dorsal root ganglia drives nociceptor excitability independently of cartilage loss, while NGF/TrkA sensitization amplifies pain through TRPV1 and substance P upregulation.
When a patient with mild radiographic OA reports severe pain, or a patient with bone-on-bone changes reports tolerable symptoms, the molecular dissociation between structural damage and pain signaling is the explanation.
This also explains the tanezumab safety signal: NGF promotes angiogenesis and nerve ingrowth into the joint, and systemic inhibition disrupted protective signaling in bone, leading to rapid OA progression and fractures in a subset of patients.
For counseling patients on why no disease-modifying OA treatment exists: TGF-β is protective in cartilage but harmful in subchondral bone, meaning any systemic modulation of a shared pathway risks off-target damage. Single-target systemic therapy is structurally prone to failure in a whole-joint disease with context-dependent signaling.