Duration of an MRI of the knee

The duration of an MRI from the knee varies depending on the problem and the performance of the device. In general, the newer the MRI machine and the fewer shifts are worked, the faster the examination is completed. In general, the duration of an MRI examination of the knee can be assumed to be 20 – max. 40 minutes. If contrast medium has to be given, the duration can be further extended.

Alternatives to MRI

In most cases, the examination of the knee joint using an MRI machine is the best way to assess the structures located there. Since structures such as ligaments (especially cruciate ligaments), cartilage (including cartilage damage and meniscus damage) and connective tissue can also be easily recognized and differentiated by the knee in the MRI, the examination with the use of this device is in many cases without alternative. This is especially a problem for patients with claustrophobia, as they have to lie in a small tube for a long time during the examination.

This claustrophobia can often be eliminated by using new MRI devices which are “open” (open MRI ́s). The use of sedatives can also help to reduce the anxiety of these people.MRI of the knee joint is the preferred method for children and pregnant women because, according to current medical knowledge, the magnetic field has no effect on the human body. Especially in contrast to the use of diagnostic methods that work with X-rays, this is an advantage for the MRI examination of children and pregnant women.

Alternatives to the examination with magnetic resonance imaging must be found if there are contraindications for the examination. In these cases, imaging methods using X-rays and ultrasound must be used. It must be noted, however, that differentiation of the affected structures is very difficult or even impossible when using these examination methods.

MRT around the meniscus

In the MRI, the two menisci appear as two wedges in the view from the front, which rest on the lower part of the knee joint on the left and right. The view from above shows the menisci like two C ́s or crescents with the opening to each other, the outer meniscus is almost closed. In a healthy meniscus, the black of the cartilage is continuous; there should be no bright spots or stripes.

An MRI examination is the method of choice if a meniscus tear is suspected. If the meniscus is torn, synovial fluid flows through the newly created gap, which is bright in the T2 image and thus stands out from the surrounding cartilage. In the T1 image technique, a light line may also be visible in the otherwise dark meniscus, but this may be a sign of degeneration.

In addition, an altered shape of the surface of the menisci can be detected, which is normally smooth and even. In the case of meniscus degeneration, you can see in the MRI that the otherwise uniform coloration of the cartilage has disappeared, and bright areas, so-called signal elevations, appear. The surface of the meniscus is no longer smooth but frayed.

Furthermore, cracks, contour irregularities and detached cartilage parts can be found. With a meniscus damage the otherwise black structure is no longer continuous, but there are spotty or streaky brightenings, which indicate cracks or damage to the cartilage. The otherwise even surface can be interrupted and frayed. Degenerative meniscus damage begins centrally and spreads outwards. They can be classified into different degrees:

Central
Horizontal, not reaching the surface
Band-shaped and reaching the surface (from here on we speak of meniscus tear)
Multiple