Crucial anatomic ensemble of the lateral knee: the 'W' configuration

To review the normal anatomy, imaging appearance, and associated pathologies of the 'W' configuration of the knee-formed by the biceps femoris tendon, fibular collateral ligament (FCL), anterolateral ligament (ALL), and iliotibial band (ITB)-and to highlight its value as an anatomical and imaging landmark in assessing lateral knee instability.

A structured review of the posterolateral and anterolateral corners of the knee was performed, focusing on the 'W' configuration. Emphasis was placed on magnetic resonance imaging (MRI) assessment, particularly coronal and sagittal planes, to evaluate normal anatomical features and detect structural disruptions.

The posterolateral and anterolateral corners form a complex stabilising framework, with the 'W' configuration serving as a key anatomical and imaging landmark. MRI is the primary diagnostic modality for visualising this configuration. Disruption of the 'W' pattern commonly indicates injury, including biceps femoris tendon tears, FCL ruptures, ALL injuries, ITB syndrome, and ITB ruptures, frequently associated with cruciate ligament tears. Isolated injuries are uncommon, with most cases involving multiligamentous trauma.

Recognition of the 'W' configuration improves diagnostic accuracy in evaluating lateral knee injuries. While mild injuries may be managed conservatively, high-grade tears-particularly those involving the posterolateral corner or causing rotational instability-often require surgical repair. Understanding this anatomical framework supports appropriate treatment planning and optimises patient outcomes in lateral knee instability.