The knee x-rays (frontal & lateral) show –

1. Air in the knee joint.

2. Fractured patella.

3. Evidence of dressing on the anterior knee with skin breach.

Air in the knee joint in the context of skin breach and patella fracture indicates a compound injury and the patient needs emergency washout of the knee. The air/ fluid pattern on HBL view should not be mistaken for a fat/ fluid interface or lipohaemarthrosis.