Infrapatellar Fat Pad Dynamics in Knee Pathologies

The infrapatellar fat pad (IFP), also known as Hoffa’s fat pad, is a triangular intracapsular structure located beneath the patella and posterior to the patellar tendon. Historically viewed as a passive mechanical cushion, the IFP is now recognised as an active participant in knee homeostasis and disease. It secretes a range of adipokines and inflammatory mediators that influence cartilage metabolism, synovial inflammation and subchondral bone remodelling. Under mechanical overload or injury, the IFP undergoes morphological changes including increased vascularisation, fibrosis and infiltration by immune cells, notably macrophages with distinct polarisation states. Such alterations contribute to the onset and progression of osteoarthritis (OA) through cartilage degradation, osteophyte formation and pain sensitisation. Magnetic resonance imaging (MRI) studies have identified hypointense signals and volume changes in the IFP that correlate with structural damage and clinical symptoms. Beyond OA, emerging data suggest the IFP may play roles in rheumatoid arthritis, post‐traumatic joint degeneration and chronic anterior knee pain. Its rich innervation renders it a significant nociceptive source, while its perivascular niche harbours mesenchymal stem/stromal cells (MSCs) that offer potential for cell‐based therapies. Understanding the dynamic interplay between mechanical, inflammatory and reparative processes within the IFP is crucial for the development of targeted interventions to mitigate knee pathology and improve patient outcomes.

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Infrapatellar Fat Pad Dynamics in Knee Pathologies publication trend

The graph below shows the total number of articles in infrapatellar fat pad dynamics in knee pathologies across all publications each year (not limited to Nature Index journals).

Technical terms

Infrapatellar fat pad (IFP): An intracapsular adipose structure beneath the patella that contributes to knee biomechanics and secretes bioactive molecules.

Osteoarthritis (OA): A degenerative joint disorder characterised by cartilage breakdown, subchondral bone remodelling and synovial inflammation.

Inflammaging: Chronic, low-grade inflammation associated with ageing that promotes tissue degeneration.

Macrophage polarisation: The process by which macrophages adopt distinct functional phenotypes (e.g. pro-inflammatory M1 or anti-inflammatory M2) in response to environmental cues.

Adipokine: A cytokine secreted by adipose tissue that regulates metabolic and inflammatory pathways.

References

1. Blockage of Osteopontin‐Integrin β3 Signaling in Infrapatellar Fat Pad Attenuates Osteoarthritis in Mice. Advanced Science (2023).
2. The infrapatellar fat pad in inflammaging, knee joint health, and osteoarthritis. npj Aging (2024).
3. Infrapatellar fat pad adipose tissue-derived macrophages display a predominant CD11c+CD206+ phenotype and express genotypes attributable to key features of OA pathogenesis. Frontiers in Immunology (2024).
4. Hypointense signals in the infrapatellar fat pad assessed by magnetic resonance imaging are associated with knee symptoms and structure in older adults: a cohort study. Arthritis Research & Therapy (2016).
5. Infrapatellar Fat Pad/Synovium Complex in Early-Stage Knee Osteoarthritis: Potential New Target and Source of Therapeutic Mesenchymal Stem/Stromal Cells. Frontiers in Bioengineering and Biotechnology (2020).