MRI Knee — routine internal derangement
From above the suprapatellar pouch to below the tibial tuberosity, including the whole patella, both menisci and the proximal tibiofibular joint.
Typical, not policy
Timings, volumes and delays here are representative values drawn from published guidance. Scanner generation, injector, cardiac output and local preference all move them. Confirm against your department's own protocol before you rely on a number.
When to use it
- Suspected meniscal or cruciate ligament tear after acute injury or with mechanical symptoms.
- Locking, giving way or persistent effusion of uncertain cause.
- Suspected osteochondral injury or spontaneous osteonecrosis.
- Assessment of cartilage and subchondral marrow before joint-preserving surgery.
- Patellofemoral instability with suspected medial patellofemoral ligament injury.
Technique
- Fluid-sensitive fat-suppressed intermediate-weighted or proton-density fast spin-echo in all three planes is the backbone; echo times of roughly 30-40 ms give the cartilage, meniscal and marrow contrast this protocol depends on.
- A non-fat-suppressed intermediate-weighted or proton-density sequence in at least one plane for meniscal morphology.
- Sagittal plane angled slightly to the anterior cruciate ligament improves its visualisation along its length.
- Slice thickness of the order of 3 mm or less with a small field of view; thicker slices volume-average small meniscal tears away.
Where it goes wrong
- Field of view and slice thickness inherited from a general protocol, producing partial volume across the menisci.
- Fat suppression failing at the periphery of the field of view, most often over the medial or lateral compartment.
- Coverage clipping the suprapatellar pouch or the patella, so an effusion volume or a patellar lesion is under-assessed.
- Adding gadolinium for a mechanical question, where it contributes nothing.
- Motion in a painful knee producing blurring at exactly the resolution the diagnosis depends on.
Clinical questions that reach this study
Contrast
None
- Unenhanced. Contrast belongs to suspected infection, tumour and synovial proliferative disease, not to meniscal or ligament assessment.
Acquisition
- Breathing
- Not applicable. Immobilisation in a dedicated knee coil is the quality determinant.
- Preparation
- No preparation. Confirm the side and give the mechanism of injury and any locking or instability. Metalwork from previous ligament reconstruction should be declared; it affects both safety screening and sequence selection.
Safety checks this protocol carries
Derived from the contrast agent and phases above, not authored here — which is why they cannot drift apart from what the protocol actually does.
- MR safety screening for implants and foreign bodies· radiographer at scan