The advent of MRI heralded a new era in musculoskeletal imaging and sounded the end of the routineuse of invasive imaging tests, such as arthrography. Non invasive MRI is now the routine modality of choice in investigating most joints. Specifically in relation to the knee, MRI has the ability to visualise normal and pathological conditions of menisci, ligaments, joint capsule, tendons, cartilage, subchondral bone marrow oedema and intra-articular bodies.
One of the most common clinical scenarios in the clinical and imaging assessment of knee trauma is the integrity of the meniscus and whether a tear is present that may warrant arthroscopic debridement. Other important consequences of trauma includes instability, with the anterior cruciate ligament (ACL) the most important stabiliser. The ACL is typically completely torn when injured and often occurs inconjunction with other ligament injuries, as well as meniscal tears and chondral defects. An isolated tear of the ACL is often a straightforward clinical diagnosis, however with concomitant injury of other structures, pain inhibition frequently precludes an adequate clinical examination, in which case either MRI or and/or arthroscopic assessment are required.
Figure 7. Sagittal MRI of the knee in a patient presenting with instability following a twisting injury demonstrates mid substance rupture of the anterior cruciate ligament (arrow).
Figure 8. Sagittal MRI of the knee in a 54 year old male following a twisting injury reveals hyperintense (bright) signal in keeping with fluid, extending to the undersurface of the posterior horn of the medial meniscus, in keeping with a tear.
MBS item description
Referral by a medical practitioner (excluding a specialist or consultant physician) for a scan of knee following acute knee trauma for a patient 16 years or older with:
- inability to extend the knee suggesting the possibility of acute meniscal tear; or
- clinical findings suggesting anterior cruciate ligament tear
MRI scans that are eligible for the Medicare rebate referred by GPs are bulk billed at Melbourne Radiology Clinic.
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