Magnetic resonance imaging of anatomical variations in the knee. Part 1: ligamentous and musculotendinous.

Magnetic resonance imaging (MRI) is now the modality of choice for the investigation of internal derangement of the knee. Technological advances, including the wider availability of stronger magnets and new sequences, allows improved visualisation of smaller structures. Normal variants must be recognised as such, so that both over-investigation and mis-diagnosis are avoided. This article reviews both the well-recognised and the less common ligamentous and musculotendinous anatomical variants within the knee and illustrates their imaging characteristics on MRI.