First and second year — the floor first, then every step
A lipohaemarthrosis on the lateral knee radiograph means an intra-articular fracture; CT maps the split, the depression and the columns, and gives the step-off and widening numbers the surgeon plans from.
Orient first
The lateral plateau is involved far more often (valgus force); a medial plateau fracture implies a higher-energy injury and is associated with knee dislocation and vascular injury.
SPLIT is a vertical fracture separating a fragment; DEPRESSION is the articular surface pushed down. Most fractures are a mix, and the classification is built on which.
A fat–fluid level in the suprapatellar bursa on a horizontal-beam lateral means marrow fat has escaped into the joint — there is an intra-articular fracture even if you cannot see it.
Acquire the study
AP and HORIZONTAL-BEAM lateral of the knee (the lipohaemarthrosis needs a horizontal beam); obliques if CT is not immediately available.
The manoeuvre
Horizontal-beam lateral view: a fat–fluid level in the suprapatellar bursa.
AP: lateral plateau contour and the joint line — a step, a double contour or a sclerotic band of depression; lateral condylar widening beyond the femoral condyle.
AP view: the fibular head, the tibial spines, and the Segond fracture (a lateral capsular avulsion at the tibial rim — ACL tear marker).
What confirms it
A fracture line reaching the articular surface of the plateau, or a lipohaemarthrosis with a plateau cortical break.
What licenses you to exclude it
A normal AP radiograph does not exclude a plateau fracture when there is a lipohaemarthrosis — CT is required.
The classic misread
Calling a knee normal with a lipohaemarthrosis present.
Reporting the injury
Classification to use
Schatzker I–VI: I lateral split; II lateral split-depression; III lateral pure depression; IV medial plateau; V bicondylar; VI metaphyseal–diaphyseal dissociation. The three-column CT concept (lateral, medial, posterior) is increasingly used alongside — state what you use.
Measurements — and how to take them
Articular depression: from the intact subchondral line of the plateau to the deepest depressed articular fragment, in mm on coronal or sagittal.
Condylar widening: the lateral edge of the tibial plateau beyond the femoral condyle on coronal, in mm.
Articular step-off and gap in mm (a step-off of about 2–3 mm is a commonly cited operative threshold — verify).
What to report
Schatzker type and the columns involved.
Maximal articular depression and step-off; split fragment and condylar widening; metaphyseal extension.
Tibial spine and fibular head fractures; lipohaemarthrosis.
On MRI: meniscal tear or entrapment, ligaments.
How to report it
CT: "Lateral tibial plateau split-depression fracture (Schatzker II) with maximal central articular depression of 9 mm and 6 mm lateral condylar widening. No medial or posterior column involvement. Associated fibular head fracture."
What not to report
Do not describe depression as "minimal" — give the mm.
Associated injuries to look for
Meniscal tears (lateral with Schatzker II), ACL and collateral injury, peroneal nerve, popliteal artery injury and compartment syndrome with medial (IV) and high-energy (V/VI) fractures.
What changes management
Articular depression or step-off beyond the operative threshold, condylar widening, and instability — operative fixation.
Schatzker IV–VI — assess the popliteal artery (ankle–brachial index or CTA).
See it on real cases
Direct links to Radiopaedia — the reference article and worked cases with their images. Each opens on Radiopaedia.