CASE 11149 Published on 11.12.2013

Synovial haemangioma in the infrapatellar fat pad

Section

Musculoskeletal system

Case Type

Clinical Cases

Authors

Castro R, Oliveira I, Fernandes T, Madureira AJ

Radiology Department
Hospital de São João,
Porto, Portugal;
Email:rcastro83@sapo.pt
Patient

25 years, female

Categories
Area of Interest Musculoskeletal system, Musculoskeletal soft tissue ; Imaging Technique MR
Clinical History
A 25-year-old woman presented with 9 months history of swelling of the anterior aspect of the left knee associated with pain during knee flexion. There was no history of traumatic injury, complaints in other joints or systemic symptoms.
Imaging Findings
The initial plain film demonstrated opacification of the infrapatellar (Hoffa’s) fat pad, which contained a small ovoid calcification. No other relevant radiographic abnormalities were noted.
MRI showed a lobulated mass in the infrapatellar fat pad, with invasion of the patellar tendon anteriorly. This lesion demonstrated marked high signal intensity on fluid-sensitive sequences and intermediate signal on T1-weighted images. Fluid-fluid levels and an internal small focus of low signal in all sequences was also noted, in keeping with the phlebolith depicted in the plain film.
There was no joint effusion, marrow signal abnormality or other abnormalities.
Discussion
Synovial haemangioma is an uncommon benign vascular malformation that occurs most frequently around the knee, but has also been reported in other joints and tendon sheaths. It may occur as a focal or diffuse lesion. The average age of onset is adolescence and early adulthood [1].
The initial clinical presentation often includes pain, swelling, mechanical symptoms and haemarthrosis. On examination, the mass is frequently palpable, compressible and spongy [2].
Plain films are normal or non-specific, often demonstrating a soft tissue mass. Phleboliths are occasionally seen.
MR imaging features of synovial haemangioma are frequently very characteristic. Generally there is a lobulated mass, with low to intermediate signal on T1 weighted images and marked hyperintensity on fluid sensitive sequences, reflecting blood pooling in vascular spaces. Thin hypointense fibrofatty septa can be present. Identification of fluid/fluid levels in the vascular spaces and small rounded signal voids compatible with phleboliths are not uncommon [3]. Siderotic synovitis associated with repetitive episodes of haemarthrosis presents with synovial thickening and hypointensity, more pronounced on gradient echo images. Sometimes the lesion can infiltrate the surrounding soft tissues.
Treatment usually consists of open or arthroscopic surgical excision. Recurrence is common in cases of diffuse synovial haemangioma [4].
Differential Diagnosis List
Synovial haemangioma
Synovial osteochondromatosis
Pigmented villonodular nodular synovitis
Final Diagnosis
Synovial haemangioma
Case information
URL: https://www.eurorad.org/case/11149
DOI: 10.1594/EURORAD/CASE.11149
ISSN: 1563-4086