Ultrasound is particularly suitable for examining soft tissues, including joint structures, tendons, ligaments, muscles, blood vessels and nerves.
Bone changes
Erosions (tiny bone changes in the joint) can often be detected earlier by ultrasound than on an X-ray. Among other things, this is very important for the early diagnosis of rheumatoid arthritis.
Many orthopaedic and rheumatological questions can therefore be answered early with ultrasound. The findings are highly relevant for further diagnosis and treatment.
In osteoarthritis, depending on how irritated the joint is, there is an effusion, the joint space appears narrowed with changes in contour, and the joint is stable.
In arthritis, there is also a joint effusion with a lifted capsule, and the joint space appears widened. The bone contours show the erosions typical of arthritis.
Fluid in the joint (effusion)
Some chronic diseases (e.g. rheumatism, gout) but also injuries (e.g. meniscus damage, cruciate ligament injury) often cause swelling in the joint. Ultrasound can clearly show both the extent (large or small) and the nature of the effusion (recent or older, due to injury or rheumatic).
On the ultrasound image, the fluid in the joint shows up as a lifted joint capsule. Because the effusion does not reflect the sound waves, the bone line appears much brighter.
When the joint is moved, the fluid can be seen shifting; for example, with the knee slightly bent, the effusion moves from the knee joint into the adjacent part of the thigh. In patients with rheumatism, ultrasound is less important for the initial diagnosis of an effusion than for showing the thickness of the synovial membrane and the size of the effusion in order to monitor the course of treatment.