Table 2 Comparison of different imaging methods for Hoffa’s fat pad alterations

Resolution

High resolution for superficial structures.

Superior resolution for deeper and complex soft tissues.

N/A

N/A

Albano et al., 2020 [23]

Dynamic Assessment

Allows real-time imaging during motion (e.g., impingement sign).

Limited to static imaging.

N/A

N/A

Albano et al., 2020 [23]

Cost

Low cost and widely available.

Expensive and less accessible.

N/A

N/A

Basha et al., 2020 [10]

Time Efficiency

Quick procedure (10–15 min).

Time-consuming (30–60 min).

N/A

N/A

Basha et al., 2020 [10]

Portability

Highly portable; can be used bedside.

Requires a fixed setup in specialized facilities.

N/A

N/A

Basha et al., 2020 [10]

Doppler Sensitivity

Identifies low-velocity blood flow (e.g., RI < 0.6).

Cannot evaluate blood flow directly.

N/A

N/A

Basha et al., 2020 [10]

Standardization

Operator dependent; variability in quality.

Consistent, standardized imaging.

N/A

N/A

Albano et al., 2020 [23]

Soft Tissue Assessment

Limited for deep structures.

Excellent for deeper structures like cartilage and ligaments.

N/A

N/A

Albano et al., 2020 [23]

Utility for Fat Pad

Effective for detecting inflammation (e.g., size > 10 mm, Doppler signal).

Ideal for detecting structural degeneration.

N/A

N/A

Vera-Perez et al., 2017 [22]

Thickening of Hoffa’s Fat Pad

Increased echogenicity and visible thickening.

Thickening and increased signal intensity in T2-weighted images.

Increased stiffness in elastography.

May indicate chronic inflammation or edema due to mechanical pressure.

Basha et al., 2020 [10]; Shin-Low et al., 2021 [30]; Manske et al., 2023 [34]; Shummalieva et al., 2023 [46]; Park et al., 2013 [51]; Subhawong et al., 2010 [28]

Lipid Infiltration

Mixed or elevated echogenicity areas

Increased signal intensity in T1-weighted sequences without fat suppression.

Heterogeneous elasticity with areas of softer consistency.

Obesity can lead to lipid accumulation, altering composition and mechanical properties.

Saxena et al., 2013 [9]; Park et al., 2013 [51]; Abelleyra et al., 2023 [54]

Fibrosis

Heterogeneous structure with areas of increased echogenicity.

Areas of low signal intensity in all sequences, indicating fibrotic tissue.

Increased stiffness in elastography, indicating fibrotic changes.

Develops due to chronic inflammation or repeated injuries, altering elasticity.

Shin-Low et al., 2021 [30]; Park et al., 2013 [51]; Gilliland et al., 2011 [52]; Calcaterra et al., 2020 [55]; Marginean et al., 2019 [56]

Lesions and Microlesions

Focal areas of altered echogenicity, potentially with signs of fiber discontinuity

Signal alteration areas with possible discontinuity in T2-weighted images.

Variable elasticity, possibly softer in lesion areas.

Acute or chronic lesions may be due to increased mechanical stress.

Saxena et al., 2013 [9]; Gilliland et al., 2011 [52]; Sakowicz et al., 2022 [57]; Manske et al., 2023 [34]

Edema

Homogeneous decrease in echogenicity.

Signal intensity increase in T2-weighted sequences, especially in fat-sat or STIR images.

Decreased stiffness or increased elasticity in edematous areas.

Indicates fluid accumulation and acute inflammation, altering elasticity.

Shin-Low et al., 2021 [30]; Basha et al., 2020 [10]; Gilliland et al., 2011 [52]; Sakowicz et al., 2022 [57]; Manske et al., 2023 [34]; Marginean et al., 2019 [56]

Altered Vascularization

Presence of increased flow signals on Doppler ultrasound.

Abnormal signal intensity or flow voids on contrast-enhanced MRI scans.

N/A

Indicates increased blood flow due to inflammation or neovascularization.

Basha et al., 2020 [10]; Herouvi et al., 2023 [53]

Area/Volume Alterations

Reduction in Hoffa’s fat pad size during progression of knee osteoarthritis.

Smaller size is associated with radiographic progression of knee osteoarthritis.

N/A

Alterations might include changes in overall volume, contour irregularities, or alterations in the fat pad configuration.

Calcaterra et al., 2020 [55]; Shummalieva et al., 2023 [46]; Testini et al., 2024 [58]