MRI features of some uncommon causes of painful knee

Aim of the work: The purpose of this study is to describe the MRI features of some uncommon causes of knee pain. Materials and methods: This is a retrospective study. We reviewed our database including the last 1000 knee MRI examinations done within the period from January 2012 till June 2013. This revision revealed 12 cases with reported variable uncommon diagnoses explaining knee pain. Unenhanced MRI of the knee was performed and included sagittal T1, T2, T2* and proton density fat suppression (PDFS), axial T2 and coronal PDFS. Some cases had complementary CT assessment. Results: The selected 12 cases included the following; three cases of supero-lateral Hoffa’s pad of fat edema expressing edema signal at the superolateral aspect of the Hoffa’s pad of fat. Three cases with fabella syndrome with chondral and subchondral edema signal at the posterior aspect of the lateral femoral condyle. Two cases with symptomatic bipartite patella showing marrow edema around the patellar synostosis. One case with proximal tibio-fibular synostosis evident on MRI as bony fusion. Two cases with quadriceps (suprapatellar) fat-pad impingement syndrome manifested as edema signal within the supra-patellar fat-pad and lastly one case with lipoma arborescence seen as frond like projections with fat signal protruding into the supra-patellar bursa. Conclusion: MRI is a useful tool in evaluation of some uncommon causes of painful knee.