"An ankle joint effusion is best seen as a teardrop-shaped soft tissue density displacing the anterior fat pad on a lateral film and lying superior to the talar neck. Effusion within the posterior recess is usually less well-defined. Plain films are sensitive for effusions >5 mL, with US and MRI being more sensitive for smaller effusions 3."
"Hip joint effusions are easiest identified on US, CT and MRI. They are difficult to identify on plain radiographs with only one reliable sign described 5:"
Expected headings
"Knee joint effusion"
"Elbow joint effusion"
"Ankle joint effusion"
"Hip joint effusion"
"Knee joint effusion"
"Elbow joint effusion"
"There is normally only a small amount of physiological intra-articular fluid. Abnormal fluid accumulation can result from inflammation, infection (i.e. pus) or trauma and might be exudate, transudate, blood and/or fat. As part of an arthrogram, deliberate injection into the joint space of a contrast medium results in an iatrogenic effusion."
"Hip joint effusions are easiest identified on US, CT and MRI. They are difficult to identify on plain radiographs with only one reliable sign described 5:"
"Evaluation begins with probe placement just cephalad to the patella, allowing identification of the quadriceps tendon in the near field and cortex of the femur in the far-field; between these two structures lies the suprapatellar recess of the knee joint, intercalating between the suprapatellar and prefemoral fat pads. Caudad angulation allows visualisation of the lateral and medial joint recesses. An effusion will cause distension of the visualised recesses with fluid, which may be anechoic or of mixed echogenicity. No internal colour flow Doppler signals should be detected, and probe compression should result in a change in shape or internal movement within the collection 7."