Sulcus angle (knee)

Last revised by Dr Bálint Botz on 29 Mar 2022

The sulcus angle is useful in the assessment of patellofemoral instability and trochlear dysplasia

Measurement

The angle is formed by the trochlear opening of the knee, measuring the angle between the medial and lateral facets. Classically described in axial x-rays of the knee performed at 30-45º of flexion (skyline view), it is valuable in both CT and MR studies.

Interpretation

Its normal value is 135±10º. When the angle of the groove is >145-150º, trochlear dysplasia can be diagnosed. This condition reflects an incongruence in the patella's sliding over the femoral trochlea, which can result in patellofemoral instability.

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Cases and figures

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