Soft tissue chondroma of the Hoffa fat pad

Hoffa’s fat
pad abnormalities, knee pain and magnetic resonance imaging in daily practice. Extraskeletal chondroma, Sagittal proton density with fat saturation image shows a heterogeneous mass within the fat pad, with high signal of chondroid matrix and oedema and low signal of calcification or ossification (courtesy of Dr. L. Pietrobono, IRCCS Policlinico San Matteo, Pavia)
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Soft tissue
chondroma of the Hoffa fat pad • Intracapsular chondroma - knee - Ganzer Fall bei Radiopaedia
Haouimi A, Intracapsular chondroma - knee. Case study, Radiopaedia.org (Accessed on 05 Jan 2023) https://doi.org/10.53347/rID-69385 • CC by-nc-sa 3.0 (modified)
Soft tissue
chondroma of the Hoffa fat pad • Giant para-articular chondroma of the infra-patellar Hoffa's fat pad - Ganzer Fall bei Radiopaedia
Ibrahim D, Giant para-articular chondroma of the infra-patellar Hoffa's fat pad. Case study, Radiopaedia.org (Accessed on 05 Jan 2023) https://doi.org/10.53347/rID-92338 • CC by-nc-sa 3.0 (modified)
Soft tissue
chondroma of the Hoffa fat pad • Intracapsular chondroma of the knee - Ganzer Fall bei Radiopaedia
Haouimi A, Intracapsular chondroma of the knee. Case study, Radiopaedia.org (Accessed on 05 Jan 2023) https://doi.org/10.53347/rID-62450 • CC by-nc-sa 3.0 (modified)
Soft tissue
chondroma of the Hoffa fat pad • Intracapsular chondroma - knee - Ganzer Fall bei Radiopaedia
Haouimi A, Intracapsular chondroma - knee. Case study, Radiopaedia.org (Accessed on 05 Jan 2023) https://doi.org/10.53347/rID-91674 • CC by-nc-sa 3.0 (modified)
Soft tissue
chondroma of the Hoffa fat pad • Intracapsular chondroma - knee - Ganzer Fall bei Radiopaedia
Haouimi A, Intracapsular chondroma - knee. Case study, Radiopaedia.org (Accessed on 05 Jan 2023) https://doi.org/10.53347/rID-150561 • CC by-nc-sa 3.0 (modified)
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Soft tissue chondroma of the Hoffa (infrapatellar) fat pad is a rare form of chondroma. It is considered by some to be the end-stage of Hoffa disease of the infrapatellar fat pad.

Clinical presentation

The condition usually presents in adults with chronic anterior knee pain as well as a hard swelling inferior to the patella.

Pathology

The pathogenesis of this condition is unclear but several theories exist. It may occur as a result of metaplasia from mesenchymal cells due to acute or repetitive trauma related to hyperextension of the knee and subsequent inflammation and hemorrhage .

Microscopic appearance
  • lobulated mass of hyaline cartilage
  • endochondral ossification in the central areas
  • variable areas of:
    • fibrocartilage
    • myxoid tissue
    • fibroadipose tissue

The variety of tissues present accounts for its heterogeneous and variable MRI appearance. 

Radiographic features

Plain radiograph

Arc-like calcifications and ossified areas in the infrapatellar fat pad, corresponding to variable endochondral ossification predominant in the central areas of the lobulated mass.

Ultrasound
  • lobular mass with acoustic shadowing
CT
  • nodular partially calcified cartilaginous mass
MRI

Features include

  • T1

    • mass in the Hoffa fat pad
    • generally low signal
    • isointense to muscle
    • some dark areas signifying calcification
  • T2: high signal in the cartilaginous components
  • PD: as above with T1, plus high intensity signal areas corresponding to medullary bone
  • GRE: prominent signal voids within a nodular mass 

Differential diagnosis

Possible considerations include

Practical points

  • it is important not to rely solely on MRI or US imaging features alone as the appearances can be variable
  • contrast enhancement can occur and does not necessarily imply malignancy
  • it is important to correlate the MRI findings with plain radiographs or CT
Siehe auch:
Assoziationen und Differentialdiagnosen zu Weichteilchondrom des Hoffa'schen Fettkörpers: