Knee ultrasound is a method of hardware diagnostics of the articulation of the lower limb formed by the articular ends of the femur and tibia and the patella. It allows to identify traumatic processes, inflammatory lesions, degenerative-dystrophic changes in bone-cartilaginous elements and periarticular soft tissues. It is carried out in anterior (longitudinal and transverse) and posterior (longitudinal, transverse, lateral and medial) projections. The patient’s position is on his back and stomach, the joints are examined in a state of extension and flexion. Ultrasound assistance is often used during puncture of the knee joint, intra-articular administration of drugs.
Knee ultrasound is prescribed for inflammatory, degenerative-dystrophic pathology, osteochondropathy, in case of suspected traumatic damage to the lateral and cruciate ligaments, menisci, patellar fracture, tumors of the bone structures of the knee joint. Arthrosonography can be performed with pain syndrome, limited mobility in the joint, the presence of deformity, palpable formation, local edema and hyperthermia, changes in muscle strength.
The variability of the echoscopic picture makes it possible to distinguish between arthritis, inflammation of the inner synovial membrane (synovitis), periarticular bags (bursitis), tendons (tendinitis), ligaments (ligamentitis), ligament ruptures, specific changes (osteophytes, aseptic necrosis, erosion), tumors, free bodies in the joint, Becker’s cyst, meniscus cysts, etc. pathology. Knee ultrasound determines the need for puncture, periarticular blockade, lavage, intra-articular administration of drugs.
Methodology of conducting
Joint echography is performed without special preparation, but it is advisable to perform echolocation no earlier than five days after intra-articular injections. Ultrasound of the lateral and anterior parts of the knee joints is performed in the position of the subject lying on his back with his limbs straightened. When examining the menisci, the patient is asked to bend his legs. Ultrasound scanning of the posterior parts of the joints is carried out when the patient turns on his stomach. For a reliable assessment of changes and the possibility of comparing structures, ultrasound of both the affected and healthy joint is performed.
Knee ultrasound is performed by poly-projection. In the antero-longitudinal projection, when the sensor is positioned above the patella, the contours of the patella, the shape and structure of the patellar (suprapatellar) bag and the presence of effusion in it, the tendons of the 4-headed thigh muscle are examined. Under the patella, the contours of the tibia, the patella’s own ligaments, the infrapatellar bag are examined.
When the sensor is rotated into an antero-transverse projection, an echographic assessment of the contours of the femur, hyaline cartilage, sections of the condyles of the femur and a cross section of the suprapatellar sac is performed. During ultrasound of the lateral medial projection of the knee joints, the condyles of the femur and tibia, lateral ligaments, articular slits, and the surface of the medial meniscus are viewed. Knee ultrasound in the posterior projections examines the bottom of the popliteal fossa, condyles of the femur and tibia, interstitial fissure, lateral meniscus, hyaline cartilage, tendons of the muscles of the posterior thigh group.
Interpretation of results
Normally, effusion in the joint cavity is not determined, joint capsules are not changed, synovial membranes are not visualized. Hyaline cartilages have smooth, clear contours, normal echostructure. The structure and integrity of the menisci are not broken; the patellae are not displaced, have a centered position. The contours of the tibia are not changed. Violations in the integrity and structure of its own patellar ligament and lateral ligaments are not determined. No additional formations are detected during knee ultrasound. Visualization of the cruciate ligaments is difficult.
In the course of ultrasound, meniscal injuries (complete and incomplete longitudinal and transverse meniscal ruptures), meniscal cysts, traumatic injuries of the lateral ligaments, rheumatoid arthritis, osteochondropathies, chondromic bodies, Becker’s cyst, tendinitis are most often determined.
The diagnostic and technical potential of ultrasound in a number of indicators exceeds CT and is not inferior to MRI of the knee joint. Unlike arthrography, CT and other radiological techniques, ultrasound of the knee joint examines not only bone, but also cartilaginous, soft tissue structures, specifies the presence, quantity and nature of articular effusion. With a sufficiently high informative value of the method, the price of ultrasound is lower than the study using MRI or CT.
The advantages of knee ultrasound in comparison with arthroscopy are non-traumatism, safety, the possibility of multiple reproduction, real-time studies when changing the position of the limb and direct communication with the patient.