A 30-year-old man sustains a knee injury in a road traffic accident. A cross-table lateral radiograph of the knee shows a fat-fluid level within the suprapatellar pouch. This finding indicates:

• A Rupture of the quadriceps tendon
• B Rupture of the popliteal cyst
• C Suppurative arthritis with gas-forming organisms
• D An intra-articular fracture communicating with the joint ✓

Explanation

Lipohemarthrosis is a fat-blood fluid level in the joint, seen best on a cross-table lateral radiograph. Marrow fat escapes into the joint only when a fracture line communicates with the synovial cavity, so its presence confirms an intra-articular fracture such as a tibial plateau fracture even when the fracture itself is not visible. Quadriceps rupture and Baker cyst rupture produce soft tissue changes without intra-articular fat, and septic arthritis does not layer fat over blood.

Reference: Rockwood and Green's Fractures in Adults, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.