Joint effusion of the knee: potentialities and limitations of ultrasonography
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This study aimed at comparing the diagnostic accuracy of ultrasonography (US) and magnetic resonance imaging (MRI) for the detection of joint effusion of the knee.
For this retrospective study, approbation by the institutional review board was not required, and written informed consent from the patients was waived. One hundred and fifty-eight patients (83 men and 75 women; median age 41.2 years; age range 13–81 years) who underwent US and MRI of the knee were included in the study. The sensitivity and specificity of US with respect to MRI in the evaluation of the effusion of the knee and in each recess were compared.
In evaluating joint effusion of the knee, compared with MRI, US correctly identified 78 of 96 patients with joint effusion, showing a sensitivity of 81.3 % and a specificity of 100 %, with a positive predictive value (PPV) of 100 % and a negative predictive value (NPV) of 77.5 % (p value = 0.001). Various results were obtained comparing ultrasound with MRI, regarding the various recesses.
US showed high specificity and sensitivity in diagnosing knee joint effusion and could be used in patients who cannot undergo MRI.
KeywordsUltrasound Magnetic resonance imaging Knee Knee effusion
Confrontare l’accuratezza diagnostica dell’ecografia (US) e la risonanza magnetica (MRI) per il rilevamento di versamento articolare del ginocchio.
Per questo studio retrospettivo, non e’ stata necessaria formale approvazione da parte del Comitato Etico, ed e’ stato derogato il consenso informato scritto. Centocinquanta pazienti (83 uomini e 75 donne; età media: 41,2 anni; range di età: 13–81 anni) sottoposti a US e MRI del ginocchio sono stati inclusi nello studio. E’ stata valutata la sensibilità e la specificità dell’ US rispetto allan MRI nella valutazione del versamento del ginocchio e in ciascun recesso.
Nella valutazione versamento articolare del ginocchio, rispetto alla MRI, l’ US ha identificato correttamente 78 su 96 pazienti con versamento articolare, mostrando una sensibilità del 81,3 % e una specificità del 100 %, con un valore predittivo positivo (PPV) del 100 % e un valore predittivo negativo (VPN) del 77,5 % (p value = 0.001). Risultati differenti sono stati ottenuti confrontando l’US con la MRI per quanto riguarda i vari recessi.
l’US ha mostrato elevata specificità e sensibilità nella diagnosi del ginocchio versamento articolare e potrebbe essere utilizzato in pazienti che non possono essere sottoposti a MRI.
Compliance with ethical standards
Conflict of interest
All authors declare that they have no conflict of interest.
All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000 (5). All patients provided written informed consent to enroll in the study and to the inclusion in this article of information that could potentially lead to their identification.
Human and animal studies
The study was conducted in accordance with all institutional and national guidelines for the care and use of laboratory animals.
Movie 1 In the anterior aspect of the knee, the suprapatellar pouch and inferior infra-hoffatic recess are evaluable with sonography. For the evaluation of the suprapatellar pouch, the quadriceps tendon is used as a landmark. Moving the transducer proximally to distally, deep to the quadriceps tendon and superficial to the femur, the suprapatellar pouch is highlighted. For the evaluation of the inferior infra-hoffatic recess, the patellar tendon is used as a landmark, deeply to the patellar tendon and fat pad of Hoffa, in touch with the tibia, the inferior infra-hoffatic recess is present (MP4 420 kb)
Movie 2 Examination of the suprapatellar pouch is performed with an extended knee, avoiding excessive probe compression, quadriceps muscle contraction and knee excessive flexion, to prevent effusion migration (MP4 661 kb)
Movie 3 In the lateral aspect of the knee, the popliteal recess and perimeniscal recesses could be evaluated with ultrasound. For the evaluation of the popliteal recess, the iliotibial tract is used as a landmark. Moving the transducer posteriorly and proximally, the popliteal recess is evaluated. Additionally, for the evaluation of the medial perimeniscal recesses, the iliotibial tract is used as a landmark. Deeply to the iliotibial tract, the perimeniscal recesses are present. In the medial aspect of the knee, medial perimeniscal recesses could be evaluated with ultrasound. The medial collateral ligament is used as a landmark. Deeply to the lateral collateral ligament, the perimeniscal recesses are present (MP4 632 kb)
Movie 4 In the posterior knee, synovial fluid can be detected in the Baker’s cyst and in the proximal tibiofibular joint. As a landmark for Baker’s cyst, the semimembranosus tendon and medial gastrocnemius muscle could be used. Once the medial gastrocnemius in the middle of the leg is identified moving the transducer proximal to the knee, the Baker’s cyst can be seen. The head of the fibula is the landmark for the evaluation of the proximal tibiofibular joint. From the head of the fibula, moving the transducer distally, effusion in the proximal tibiofibular joint is highlighted (MP4 386 kb)