Ganglion cyst of Hoffa's fat pad of knee-a rare cause of knee pain and swelling-a case report and literature review

Hoffa's fat pad ganglion cyst of the knee: a case report of a rare cause of knee pain and swelling

Introduction and importance

Hoffa's fat pad (HFP), also known as infrapatellar fat pad, is one of the three fat pads in the knee. Ganglion cyst (GC) rarely arises from HFP which presents knee pain and swelling.

Case presentation

A 43-year-old female presented with left knee pain for 1 year and swelling in her left knee for 6 months. Clinical examination revealed a palpable swelling of size around 3 cm×2 cm over the anteromedial aspect of the left knee. The size of the swelling increased on extension and decreased on flexion of the knee. A musculoskeletal ultrasound of the left knee revealed a lobulated anechoic lesion of size ∼2.3 cm×2 cm in HFP. Open excision of cystic mass through medial parapatellar approach was done, and histopathological examination showed findings consistent with GC. At 6 months follow-up, there was no residual swelling and no recurrence. She was symptom-free on her recent evaluation after 1 year of operation.

Clinical discussion

GCs arising from HFP are much rarer among the cysts around the knee. Diagnosis is primarily done by magnetic resonance imaging. However, the use of ultrasonography has grown in the diagnosis of the GC. Among different modalities of treatment, open excision is the most recommended to prevent recurrence and incomplete resection.

Conclusions

This case illustrates the importance of ultrasonography in the early diagnosis of HFP GC and reserving more costly and time-consuming imaging modality magnetic resonance imaging for localizing the extent of the cyst. We recommend an open resection to avoid recurrence and incomplete resection of the cyst.

Unusual Occurrence of Tenosynovial Giant Cell Tumor in Hoffa's Fat Pad: A Potential Differential Diagnosis for Nontraumatic Knee Swelling and Pain

A tenosynovial giant cell tumor (TGCT) is a benign lesion whose presence in Hoffa's pad has rarely been reported. This unique case report discusses a 33-year-old female patient who presented with swelling and pain in her left knee. Clinical and MRI findings were used to make the diagnosis, which was confirmed on a histopathological basis. The patient had a large tumor (5 × 3 × 3 cm) in Hoffa's fat pad, which was diagnosed as TGCT and managed with open resection due to its size. At follow-up after 20 months, the patient was asymptomatic, and there was no local recurrence of the tumor.