0313: Knee Tendons and Ligaments. Anatomy and Pathology

Abstract

In the knee, particular strengths of US include the ability to assess traumatic disease affecting tendons and some ligaments. In the quadriceps tendon, US is able to distinguish partial from complete tears thus helping clinical examination that is often misleading. In partial-thickness tears, the superficial tendon layer (from the rectus femoris) is the first involved, followed by the intermediate one (from the vastus medialis and lateralis). In complete tears, the tendon can be retracted at variable distance: the medial and lateral patellar retinacula should also be carefully evaluated because they are often involved. In patellar tendinosis (jumper's knee), chronic microtrauma between the undersurface of the patellar insertion and a prominent patellar tip has been assumed to be a causative factor for chronic impingement and secondary degenerative changes of the patellar tendon. Complete patellar tendon tears may follow a direct local injury or represent the end stage chronic tendinopathy. On the medial knee, MCL injuries can be readily diagnosed with US. Partial tears most often affect the meniscofemoral ligament and can be difficult to differentiate from complete ruptures. Pes anserinus tendinopathy is rare and presents with thickened, hypoechoic tendons and bony cortex irregularities resulting from traction injury. On the lateral knee, chronic local impingement of the iliotibial band against the lateral condyle may lead to friction, local inflammation and pain, the so called “runner's knee”. When inflamed, the bursa between the iliotibial band and the lateral condyle is distended by fluid and can be associated with iliotibial band thickening. In the intercondylar fossa, the middle and distal thirds of the PCL can be demonstrated with US as a deep thick hypoechoic band. Ganglion cysts arising in close proximity to the cruciate ligaments can be occasionally identified with US as incidental findings. A rare tendon-related pathology of the posterior knee is the popliteal artery entrapment syndrome. This syndrome is related to compression of the popliteal artery secondary to the anatomic relationships between the vessel and an abnormal medial head of the gastrocnemius or popliteus. When examining the distal biceps femoris, US scanning should be extended cranially to include the musculotendinous junction as it is a common site of sport-related injuries.