MRI features of some uncommon causes of painful knee

This work was not presented anywhere.

Available online 20 February 2014

Figures & data

Table 1 Summary of the demographic, clinical and MRI features of the cases included in this study.

Diagnosis	Number	Age & sex	Complaint	MRI features
Fabella syndrome	3	2 Females 18 and 30 years	Pain at the lateral posterior aspect of the knee with localized tenderness.	Edematous changes were noted at chondral and subchondral marrow portion of the posterior aspect of lateral femoral condyle.
		One male 25 years
Symptomatic bipartite patella.	2	2 Males 17 and 21 years	Chronic pain at anterior aspect of the knee with elicited tenderness at the patella.	Bipartite patella with edematous marrow changes around the junction of the accessory and main patella.
Quadriceps fat-pad impingement syndrome.	2	1 Male 25 years	Chronic pain at anterior aspect of the knee especially during walking with tenderness just above the patella.	Low T1 and high T2 signal at the small supra-patellar pad of fat with high signal on the PDFS sequences.
		1 Female 27 years
Proximal tibio-fibular synostosis.	1	Male 22 years	Chronic pain at lateral aspect of the knee and upper leg.	Bony over growth and communication at proximal tibiofibular articulation and upper shafts of the fibula and tibia
Lipoma arborescence	1	1 Male 42 years	Knee anterior, superior knee mild pain lasting for years ago and supra-patellar swelling	Villous like synovial lesions protruding into the supra-patellar bursa expressing fat signal intensity (T1 and T2 high signal that dropped on PDFS).
Superolateral Hoffa’s fat pad edema.	3	2 Females 42 and 36 years	Chronic pain at anterior aspect of the knee with clinically elicited tenderness just lateral and inferior to the patella.	Low T1 and high T2 signal at the superior lateral portion of the infrapatellar fat pad with high signal on the PDFS sequences.
		1 Male 38 years

Figure 1 Sagittal T2 (a), sagittal T1 (b) and sagittal PDFS (c) demonstrated edematous changes noted at chondral and subchondral portion of the posterior aspect of lateral femoral condyle with a related small fabella, no chondral defects seen. Features are suggestive of fabella syndrome.

Figure 2 Axial T2 (a), coronal PDFS (b) and sagittal PDFS (c) demonstrated bipartite patella type III with marrow edema within the bipartite fragment with thinning and irregularity of the intervening cartilage, reflecting symptomatic bipartite patella. Mild joint effusion is also seen.

Figure 3 Sagittal T2 (a), sagittal T1(b) and sagittal PDFS (c) demonstrated suprapatellar pad of fat impingement syndrome manifested as low T1 and intermediate T2 signal at the small supra-patellar pad of fat with high signal on the PDFS sequences while the infra-patellar pad of fat and the subcutaneous fat showed drop of signal. The overlying quadriceps tendons as well as the patella were unremarkable.

Figure 4 Sagittal T2 (a) and sagittal T1 (b) demonstrated bony communication noted partially at proximal tibiofibular articulation and also involve the upper shafts of the fibula and tibia with relative deformity of the fibular head reflecting synostosis which was clearly evident on complementary CT (c). The signal was that of marrow without signal alteration noted or effusion within the proximal tibiofibular joint.

Figure 5 Sagittal T1 (a) and axial T2 (b) demonstrated villous like synovial lesions protruding into the supra-patellar bursa that is distended by effusion. These lesions express fat signal intensity that dropped on T2 fat suppressed coronal images (c and d). CT (e) proved the fatty nature of the lesion.

Figure 6 Sagittal PDFS (a) axial PDFS (b) and coronal PDFS demonstrated focal high signal denoting edema at the superior lateral portion of the Hoffa‘s pad of fat matching with superior lateral pad of fat impingement syndrome.