In lipedema, subcutaneous adipose tissue is in a state of chronic low-grade inflammation, characterized by infiltration of the hypodermis by macrophages and perivascular mast cells [[13], [15]]. Sustained activation of these cells results in continuous release of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), as well as vasoactive mediators and growth factors cells [[16]].

Figure 1.Inflammatory axis of the pain mechanism in lipedema.

This inflammatory microenvironment profoundly alters the architecture and physiology of adipose tissue, stimulating extracellular matrix remodeling, collagen deposition, increased vascular permeability, and protein-rich interstitial edema. This mechanism may explain the disproportionate pain in response to mechanical stimuli frequently reported by patients. From a nociceptive perspective, the persistent release of cytokines and algogenic mediators lowers the activation threshold of peripheral nociceptors in C and Aδ fibers, promoting peripheral sensitization, rendering subcutaneous tissue hyperresponsive to touch, compression, and changes in tissue pressure [[13], [17]]. However, the direct demonstration of these mediators acting on nociceptors in lipedema tissue is still being validated.

With maintenance of the inflammatory process, a progressive cycle develops: inflammation - tissue remodeling - pain - inflammatory exacerbation. In which tissue expansion and fibrosis further enhance immune cell activation. The result is a biologically active and inflamed adipose microenvironment, in which inflammation is not a secondary event but rather a primary mechanism in the genesis and perpetuation of pain in lipedema. This process is driven by chronic immune activation, leading to sustained release of cytokines and algogenic mediators and resulting in chronic, diffuse, deep pain that is disproportionate to the applied stimulus. A schematic illustration of these findings is shown in Figure 1.

Lipedema is characterized by adipocyte hyperplasia and hypertrophy. The expansion of the subcutaneous compartment volume leads to compression of the microcirculation, resulting in ischemia and consequent increased blood demand findings of a subclinical subcutaneous compartment syndrome [[18]]. The increased blood demand promotes neovascularization, which, under compressive conditions, results in immature and fragile capillaries, predisposing to hemorrhage [[5]-[7]]. Microcirculatory compression affects not only the arterial side but also venous and lymphatic pathways, contributing to edema and congestion.

Erythrocyte extravasation and hemoglobin degradation release free iron and biliverdin—molecules that are highly irritating to the hypodermis—thereby recruiting inflammatory cells that amplify nociception and promote septal fibrosis. Ischemia is also associated with increased release of hypoxia-inducible factor-1α (HIF-1α), which intensifies pathological angiogenesis and fibrosis, establishing a self-perpetuating cycle of hypoxia, inflammation, and structural damage [[9], [13]].

Histopathological findings reported by Vargas et al. demonstrate that subcutaneous adipose tissue in lipedema-affected areas exhibits microvascular alterations that define a microenvironment of chronic perfusion impairment. These include dilated capillaries, immature angiogenesis, increased permeability, erythrocyte extravasation, and interlobular hemorrhage, frequently accompanied by protein-rich interstitial edema and stromal fibrotic deposition. Collectively, these features characterize dysfunctional microangiopathy [[6]].

Immature and permeable angiogenesis, together with capillary fragility identified in biopsies, results in recurrent erythrocyte extravasation and interstitial hemoglobin release. Subsequent heme and iron degradation activates CD163+ macrophages and triggers the production of reactive oxygen species (ROS), promoting oxidative damage, interstitial edema, and fibrotic stimulation [[12]-[17], [19], [20]]. This inflammation-hemorrhage-fibrosis cycle progressively compromises oxygen transport and nutrient diffusion, leading to persistent tissue hypoxia.

Hypoxia, in turn, precipitates robust metabolic and nociceptive responses: adipocytes, endothelial cells, and matrix cells release algogenic mediators (extracellular ATP, lactate, NGF), which lower the activation threshold of peripheral nociceptors (C and Aδ fibers) [[13], [17]]. In addition, protein-rich interstitial edema and fibrosis resulting from dysfunctional angiogenesis increases local interstitial pressure, exerting mechanical compression on nerve endings and connective tissue structures. This increase in subcutaneous compartment pressure, combined with microvascular ischemia, generates pain through simultaneous compression and ischemic mechanisms [[18]].

As the condition progresses, subcutaneous tissue exhibits increasing cicatricial remodeling, with greater collagen density and reduced stromal compliance. Decreased tissue pliability alters microvascular flow dynamics and perpetuates ischemia, establishing a self-reinforcing cycle of vascular injury, fibrosis, and pain. This tissue chronicity also explains the poorer clinical response observed in intermediate and advanced stages of lipedema, in which pain becomes more persistent and disproportionate to mechanical stimuli. A schematic illustration of the hypoxic-hemorrhagic mechanism is shown in Figure 2.

Figure 2.Hypoxic-hemorrhagic axis in the pain mechanism of lipedema.

Recent reviews describe lipedema as an adipofascial disorder, in which chronic pain, edema, and nodularity are associated with profound structural alterations of the connective tissue [[16]]. The pathogenesis and development of lipedema may result from alterations in adipogenesis, inflammation, and extracellular matrix remodeling that lead to fibrosis and edema formation, and transcriptomic studies of subcutaneous tissue from patients have identified differentially expressed genes involved in these processes—including adipogenesis-related PRKG2, MEDAG, and BICC1; inflammation and macrophage polarization markers CD68, CD163, and TREM2; and pain-modulating genes such as SHTN1, SCN7A, and SLC12A2 [[19]].

Fascial remodeling with progressive thickening is thought to occur secondary to adipose tissue expansion, as a compensatory response to loss of tissue elasticity [[21]]. Fascial thickening is associated with collagen reorganization and reduced myofascial gliding, resulting in continuous mechanical tension, vascular compression, and deformation of septal tunnels that conduct neurovascular bundles [[22], [23]].

Several recent studies reinforce the concept of lipedema as an adipofascial disorder, characterized by progressive connective tissue fibrosis and thickening of septa and fascia [[21]-[24]]. These findings support the notion that, beyond the adipocytic component, there is marked thickening and remodeling of the superficial fascia and fibrous septa (retinacula cutis) in affected areas, creating a mechanically “stiffer” and less compliant tissue environment.

This mechanical dysfunction contributes both to the progression of fibrosis—leading to a functional condition resembling chronic fasciitis—and to neural entrapment, which increases pain even in the absence of overt edema. The fascia is now recognized as a highly innervated tissue, containing a rich network of nociceptive, proprioceptive, and autonomic fibers, and is capable of actively participating in pain modulation [[17]].

At the microscopic level, the collagen pattern within the fascia is critical. Alterations in collagen and elastic fiber composition modify the biomechanical properties of the fascia and plausibly represent a source of myofascial dysfunction in women. Histological studies demonstrate that in human fascia, low hormonal exposure (such as during menopause) leads to a relative increase in type I collagen with a reduction in type III collagen and fibrillin, rendering the fascia stiffer and less elastic. In lipedema, recent reviews emphasize that the disease is hormone-related and marked by extracellular matrix (ECM) remodeling, fibrosis, and altered tissue elasticity. Accordingly, collagen reorganization (increased type I collagen, denser fibers, reduced type III collagen) within the fascia and septa increases mechanical stiffness, reduces the ability to dissipate mechanical stress, and facilitates microtrauma, small nerve injury, and chronic pain during movement or compression [[21]-[23]].

Gliding between fascial planes and between muscle-fascia-adipose tissue depends on a matrix rich in low-viscosity hyaluronic acid (HA). Increased HA viscosity within the fascia is directly associated with myofascial pain; when HA becomes more concentrated and structured (“densification”), sliding between fascial layers is reduced and mechanoreceptors are activated, generating pain [[23], [24]]. Stecco et al. have demonstrated that increased HA viscosity within fascia is directly linked to myofascial pain, as densification impairs fascial gliding and activates mechanosensitive receptors [[23]]. Matteini et al. showed that highly concentrated HA solutions form stable “superstructures,” with abrupt changes in rheological properties (increased viscosity), which can be reversed by temperature elevation (gel-fluid transition) [[24]].

Figure 3.Adipomyofascial axis in the pain mechanism of lipedema.

In lipedema, chronic inflammation of adipose tissue promotes interstitial and fascial fibrosis, with collagen accumulation and thickening of septa and superficial fascia. Collagen remodeling (increased type I collagen and reduced type III collagen) renders fascia and septa stiffer and less elastic, particularly in a hormonally dependent female context. Alterations in the HA-rich matrix within the fascia increase viscosity (densification), impairing sliding between muscle, fascia, and adipose tissue. The combination of fascial thickening and matrix densification alters force transmission [[25]], generates focal stress points and micro-shear forces on free nerve endings and neurovascular plexuses, and facilitates hypersensitivity to superficial palpation, deep pain, sensations of heaviness and burning under load, and mechanical allodynia (e.g., light touch or clothing compression). A schematic illustration of the adipomyofascial mechanism is shown in Figure 3.

The environment characterized by inflammation, fibrosis, increased subcutaneous compartment pressure, hypoxia, and oxidative stress induces structural damage to sensory nerve fibers, including axonal degeneration and partial demyelination. In parallel, biochemical alterations activate transient receptor potential vanilloid 1 (TRPV1), purinergic receptor P2X3, and acid-sensing ion channel 3 (ASIC3), maintaining neuronal hyperexcitability and persistent ectopic discharges [[11], [26]]. Clinically, this manifests as allodynia, hyperalgesia, and deep pain disproportionate to the applied stimulus.

Narrowing of neural tunnels, compression, and oxidative stress lead to axonal degeneration and demyelination, while sustained activation of TRPV1, P2X3, and ASIC3 channels maintains hyperexcitability, resulting in persistent pain, although these channels have not been directly identified in adipose tissue in lipedema, since such analyses remain scarce. The molecular basis of pain in lipedema involves the integration of inflammatory, hypoxic, tissue remodeling, and mechanic transduction pathways, which together modulate the adipose microenvironment and neuronal excitability.

Figure 4.Neuromolecular axis in the pain mechanism of lipedema.

Transcriptomic and multi-omics studies demonstrate that adipose tissue in patients with lipedema exhibits gene expression patterns related to adipocyte hyperplasia, chronic low-grade inflammation, disorganized angiogenesis, and extracellular matrix alterations. From a neuromolecular perspective, oxidative stress, tissue acidosis, and extracellular ATP release activate ion channels such as TRPV1 (sensitive to heat and acidic pH), P2X3 (activated by ATP), and ASIC3 (sensitive to reduced pH), amplifying peripheral sensitization [[26]]. Sustained activation of these channels promotes spontaneous firing of C fibers, hyperalgesia, and allodynia, even in the absence of evident mechanical stimuli. Together, these processes establish a self-perpetuating circuit: inflammation - hypoxia - tissue remodeling - neural sensitization. Understanding these molecular mechanisms highlights potential therapeutic targets, including specific ion channel blockers, matrix metalloproteinase (MMP) inhibitors, receptor modulators, antifibrotic agents, and endothelial-protective strategies. Within this integrated self-reinforcing circuit (structural, inflammatory, ischemic, and neuromolecular) inflammation promotes hypoxia, hypoxia intensifies tissue remodeling, and both enhance neural sensitization, consolidating a persistent and refractory pain state [[11], [13], [26]].

This framework delineates a renewed perspective on therapeutic targets, which should aim at inflammatory modulation and improvement of tissue perfusion. Schematic illustration of the neuromolecular mechanism is shown in Figure 4.

The integrative model suggests that adipose tissue in lipedema acts as an active pain-producing organ rather than merely a lipid storage site. Therefore, therapeutic strategies focused exclusively on volumetric reduction are insufficient. Management should also encompass inflammatory modulation, restoration of microvascular perfusion, preservation of fascial function, and neuroprotection as fundamental pillars. It is noteworthy that the four axes interact and mutually reinforce one another, forming a large, interconnected network with circular and cascading feedback loops, ultimately resulting in intense chronic pain that is disproportionate to the applied stimulus.

Figure 5. Schematic illustration of the integration of pathophysiological axes in the pain mechanism of lipedema.

The authors propose a multifactorial model of pain in lipedema (Figure 5): inflammation intensifies hypoxia and fibrosis; fascial remodeling alters biomechanics and amplifies nociceptive signaling; and neuroinflammation integrates inputs from adipose tissue, the vasculature, and fascia, producing persistent, multidimensional neuropathic pain often disproportionate to adipose volume.

Obesity, venous disease, lymphedema, age, menopausal status and analgesic administration may cause confusion; affecting independently inflammation, microcirculation, fascia stiffness, and pain in lipedema. Most of the studies included are lacked matched controls or adjustments for these factors, limiting the ability to attribute observed alterations, specifically to lipedema. Therefore, while the current evidence suggests plausible pathophysiological mechanisms, the findings should be interpreted with caution.