MRI of intermittent meniscal dislocation in the knee

Area of Science:

• Orthopedics
• Radiology
• Sports Medicine

Background:

• Intermittent knee locking can be disabling, often presenting without clear signs on initial imaging.
• Conventional magnetic resonance (MR) imaging may fail to detect subtle causes of knee locking, especially when no meniscal tear is present.

Observation:

• Three patients with a history of reproducible intermittent knee locking had negative initial MR scans.
• Patients were able to voluntarily induce the knee "locked" position.
• A specialized MR imaging protocol was employed, capturing T(2) weighted sagittal and coronal views in the induced "locked" state.

Findings:

• Meniscal dislocation was evident on MR imaging in all three patients when they intentionally adopted the "locked" position.
• Initial MR scans showed normal meniscal appearance.
• Arthroscopy confirmed deficiency of meniscocapsular ligaments and meniscal instability, but no meniscal tear.

Implications:

• A normal conventional MR does not exclude meniscal dislocation as a cause of intermittent knee locking.
• Targeted MR imaging in the patient-reproduced "locked" position is a valuable diagnostic tool for subtle meniscal instability.
• This diagnostic approach can identify meniscal dislocation in cases with suggestive clinical history but negative conventional MR findings.