Melbourne Radiology Clinic
Ground Floor
Suite 3-6, 100 Victoria Parade
East Melbourne VIC 3002
Ph: 03 9667 1667
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Paediatric MRI Series – Knee

MRI Gallery - MRI of the Paediatric Knee

Paediatric MRI Series:
Knee

MRI is unparralleled when it comes to imaging of the knee. It is the most reliable non-invasive tool that is available to doctors today to diagnose disorders of the knee.

The knee is the largest joint of the body, as well as probably the most frequently injured and thefore the most commonly imaged. Frequent indications for imaging include for the assessment of meniscal tears, ligament sprains/tears, cartilage and bone injuries, fluid masses, inflammatory arthritis and surrounding tendons.

Ultrasound has a limited role in the assesment of the knee, typically to visualise superficial structures, such as the extensor mechanism (quadriceps and patellar tendons) masses and also utilised to perform any procedures, such as joint aspiration (arthrocentesis) and injection based therapies.

Meniscal tears

The most frequent reason for MRI assessment of the knee is to diagnose a meniscal tear.

The menisci are triangular fibrocartilaginous structures interposed between the femur and tibia (the two bones that make up the main compartment of the knee joint) in order to cushion the forces transmitted between these two. With trauma (and in the non-paediatric setting, age related degeneration), the menisci are prone to shear forces and therefore tearing, resulting in painful movement of the knee, a sensation of instability, catching and locking. If a tear is large enough, then the meniscus can lose most if not all of its function, thus resulting in early arthritis.

Figure 2A & 2B. In the case above, most of the medial meniscus is displaced into the intercondylar notch (arrow), with only a minimal amount remaining behind in its normal position (small double arrows). For reference, the contour of the medial meniscus should be similar to the lateral meniscus (L) and slightly larger. This is indicative of the severity of this tear as most of the meniscal tissue is flipped into the notch and consistent with known as a bucket handle tear.

MRI assessment of the knee following trauma in order to exclude a medial meniscal tear of medial collateral ligament sprain demonstrates bone marrow oedema of the medial femoral condyle consistent with a bone contusion (“bruise”). Further supportive of direct trauma is a loculated fluid collection within the overlying soft tissue, consistent with a collection of blood (haematoma). The knee was otherwise structurally intact and the patient treated with a short period of rest, pain relief and graduated return to normal activities.

Figure 3 & 4. MRI assessment of the knee in the case above demonstrates bone bruising (osseous contusion) of the medial femoral condyle (arrows) due to direct trauma, which also causes a deep soft tissue haematoma (bleed; short arrows).

Figure 5. MRI assessment of the knee following trauma in the case above reveals thickening and increased bright signal within the substance of the medial collateral ligament (arrow), in keeping with a low grade partial sprain injury.

Patellar Fracture

Figure 7 & 8. A further MRI of the knee following trauma demonstrates the presence of a small fracture in the patella (vertical dark line; arrow, left image). This is surrounded by diffuse bright signal around it, within the surrounding marrow, similar to that seen in a contusion (arrow, right image).

Patellar Dislocation

MR imaging of the knee following an episode of twisting and instability reveals contusion of the medial aspect of the patella (P) and lateral femoral condyle (F), diagnostic of an episode of lateral patellar dislocation. This occurs when the medial patellar retinaculum that holds the patellar in its position is torn (double arrows), resulting in unopposed forces from the lateral side dragging the patella,   eventually resulting in dislocation from its groove (G) when the patella relocates to its normal position (as shown below), collision occurs between the two bones to result in the pattern of bone contusions described.

Figure 9 & 10. Lateral patellar dislocation

Juvenile Chronic Arthritis (JCA).

MRI assessment of the knee in a child with a painful swollen joint demonstrates a large collection of fluid within the joint known as an effusion.

The joint is lined by specialised tissue that produces fluid known as synovium or synovial cells. When these cells become inflamed, this is known as synovitis which results in net increased production of synovial fluid and thus the accumulation of an effusion.

Inflamed synovium can be caused by many conditions, such as inflammatory arthritis (rheumatoid arthritis for example) as well as infections and degeneration. In this case, the likely diagnosis was Juvenile Chronic Arthritis (JCA).

Figure 11 & 12. MRI of Juvenile Chronic Arthritis (JCA) in a child demonstrate an excess amount of joint fluid (F) known as an effusion as well as thickening of the joint lining, known as synovitis (arrows).

MRI scans of the knee in children under 16 that are eligible for the Medicare rebate referred by GPs are bulk billed* at Melbourne Radiology Clinic.

MBS Item Description

Referral by a medical practitioner (excluding a specialist or consultant physician) for a scan of knee for a patient under 16 years where there is:

  • suspected internal joint derangement
GP Referred

BULK-BILLED*
a previous radiographic examination must have been performed