Joint effusion
Updates to Article Attributes
This article is dedicated to the humble joint effusion, particularly the plain radiographic appearances.
A joint effusion is defined as an increased amount of fluid within the synovial compartment of a joint. There is normally only a small physiological physiological amount of fluid. Abnormal fluid accumulation can result from inflammation, infection (i.e. pus) or trauma and may be an exudate, transudate, blood and/or fat.
Recognition of a joint effusion on plain radiographs can be difficult difficult, particularly for the non-radiologist. Appreciation of the typical appearances and signs of joint effusions can assist diagnosis.
Radiographic appearancefeatures
Knee joint effusion
A knee joint effusion appears as well-defined rounded homogeneous soft tissue density within the suprapatellar recess on a a lateral radiograph. The effusion will 2:
- separate peri-articular fat pads >
;10mm;10 mm - obliterate the normally crisp posterior border of the quadriceps tendon
- displace the quadriceps tendon and patella anteriorly
Lipohaemarthrosis is a particular type of effusion that occurs in the setting of intra-articular fracture where a fat-fluid level is seen due to marrow fat leaking into the joint via the fracture. Lipohaemarthrosis can occur in other joints (e.g. shoulder) but is most readily identified in the knee.
Elbow joint effusion
The sail sign is the key to recognising an elbow joint effusion. On a lateral radiograph, an effusion causes causes displacement of the anterior and posterior fat pads surrounding the distal humerus. The triangular appearance of the displaced low density fat pad simulates the appearance of a sail.
An elbow joint effusion in in the setting of trauma is very often a sign of an occult fracture In adults the occult fracture is most commonly of the radial head while in children a non non-displaced supracondylar fracture should be suspected.
{{youtube:http://www.youtube.com/watch?v=k1UYfi9zdOg}}
Ankle joint effusion
An ankle joint joint effusion is best seen as a teardrop-shaped soft tissue density displacing the anterior fat pad on a lateral film and lies superior to the talar neck. Effusion within the posterior recess is usually less well defined. Plain films are sensitive for effusions >5 mlmL with US and MRI being more sensitive for smaller effusions 3.
Hip joint 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:
- asymmetrical widening > 1 mm in teardrop distance (between lateral aspect of the pelvic teardrop and most medial aspect of femoral head)
-<p>This article is dedicated to the humble <strong>joint effusion</strong>, particularly the plain radiographic appearances. </p><p>A joint effusion is defined as an increased amount of fluid within the synovial compartment of a joint. There is normally only a small physiological amount of fluid. Abnormal fluid accumulation can result from inflammation, infection (i.e. pus) or trauma and may be an <a href="/articles/exudate">exudate</a>, <a href="/articles/transudate">transudate</a>, blood and/or fat.</p><p>Recognition of a joint effusion on plain radiographs can be difficult, particularly for the non-radiologist. Appreciation of the typical appearances and signs of joint effusions can assist diagnosis.</p><h4>Radiographic appearance</h4><h5>Knee joint effusion</h5><p>A knee joint effusion appears as well-defined rounded homogeneous soft tissue density within the suprapatellar recess on a lateral radiograph. The effusion will <sup>2</sup>:</p><ul>-<li>separate peri-articular fat pads >10mm</li>- +<p>This article is dedicated to the humble <strong>joint effusion</strong>, particularly the plain radiographic appearances. </p><p>A joint effusion is defined as an increased amount of fluid within the synovial compartment of a joint. There is normally only a small physiological amount of fluid. Abnormal fluid accumulation can result from inflammation, infection (i.e. pus) or trauma and may be an <a href="/articles/exudate">exudate</a>, <a href="/articles/transudate">transudate</a>, blood and/or fat.</p><p>Recognition of a joint effusion on plain radiographs can be difficult, particularly for the non-radiologist. Appreciation of the typical appearances and signs of joint effusions can assist diagnosis.</p><h4>Radiographic features</h4><h5>Knee joint effusion</h5><p>A knee joint effusion appears as well-defined rounded homogeneous soft tissue density within the suprapatellar recess on a lateral radiograph. The effusion will <sup>2</sup>:</p><ul>
- +<li>separate peri-articular fat pads >10 mm</li>
-</ul><p><a href="/articles/lipohaemarthrosis">Lipohaemarthrosis</a> is a particular type of effusion that occurs in the setting of intra-articular fracture where a fat-fluid level is seen due to marrow fat leaking into the joint via the fracture. Lipohaemarthrosis can occur in other joints (e.g. shoulder) but is most readily identified in the knee. </p><h5>Elbow joint effusion</h5><p>The <a href="/articles/sail-sign">sail sign</a> is the key to recognising an <a href="/articles/elbow-joint-effusion">elbow joint effusion</a>. On a lateral radiograph, an effusion causes displacement of the anterior and posterior fat pads surrounding the distal humerus. The triangular appearance of the displaced low density fat pad simulates the appearance of a sail.</p><p>An <a href="/articles/elbow-joint-effusion">elbow joint effusion</a> in the setting of trauma is very often a sign of an occult fracture In adults the occult fracture is most commonly of the <a href="/articles/radial-head">radial head</a> while in children a non-displaced <a href="/articles/supracondylar-fracture">supracondylar fracture </a>should be suspected. </p><p>{{youtube:http://www.youtube.com/watch?v=k1UYfi9zdOg}}</p><h5>Ankle joint effusion</h5><p>An ankle joint effusion is best seen as a teardrop-shaped soft tissue density displacing the anterior fat pad on a lateral film and lies 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 <sup>3</sup>.</p>- +</ul><p><a href="/articles/lipohaemarthrosis">Lipohaemarthrosis</a> is a particular type of effusion that occurs in the setting of intra-articular fracture where a fat-fluid level is seen due to marrow fat leaking into the joint via the fracture. Lipohaemarthrosis can occur in other joints (e.g. shoulder) but is most readily identified in the knee. </p><h5>Elbow joint effusion</h5><p>The <a href="/articles/sail-sign">sail sign</a> is the key to recognising an <a href="/articles/elbow-joint-effusion">elbow joint effusion</a>. On a lateral radiograph, an effusion causes displacement of the anterior and posterior fat pads surrounding the distal humerus. The triangular appearance of the displaced low density fat pad simulates the appearance of a sail.</p><p>An <a href="/articles/elbow-joint-effusion">elbow joint effusion</a> in the setting of trauma is very often a sign of an occult fracture In adults the occult fracture is most commonly of the <a href="/articles/radial-head">radial head</a> while in children a non-displaced <a href="/articles/supracondylar-fracture">supracondylar fracture </a>should be suspected. </p><p>{{youtube:http://www.youtube.com/watch?v=k1UYfi9zdOg}}</p><h5>Ankle joint effusion</h5><p>An ankle joint effusion is best seen as a teardrop-shaped soft tissue density displacing the anterior fat pad on a lateral film and lies 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 <sup>3</sup>.</p><h5>Hip joint effusion</h5><p>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 <sup>5</sup>:</p><ul><li>asymmetrical widening > 1 mm in teardrop distance (between lateral aspect of the <a title="Pelvic teardrop" href="/articles/pelvic-tear-drop">pelvic teardrop</a> and most medial aspect of femoral head)</li></ul>
References changed:
- 5. Sweeney J, Helms C, Minagi H, Louie K. The Widened Teardrop Distance: A Plain Film Indicator of Hip Joint Effusion in Adults. AJR Am J Roentgenol. 1987;149(1):117-9. <a href="https://doi.org/10.2214/ajr.149.1.117">doi:10.2214/ajr.149.1.117</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/3495970">Pubmed</a>
Unable to process the form. Check for errors and try again.