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MR appearances of the locked knee
J M Elliott1, P F Tirman, A J Grainger
1Department of Radiology, University of California, 350 Parnassus Avenue, Suite #150, San Francisco, CA 94117, USA.
The British Journal of Radiology
|March 29, 2001
Summary
Magnetic Resonance Imaging (MRI) reveals common and rare causes of a "locked knee". Meniscal tears are the primary cause, but other abnormalities blocking knee extension are also discussed.
Area of Science:
- Radiology
- Orthopedics
- Medical Imaging
Background:
- A locked knee, characterized by mechanical blockage of knee extension, can stem from various internal derangements.
- While meniscal tears are frequently implicated, a differential diagnosis is essential for accurate patient management.
Purpose of the Study:
- To review the Magnetic Resonance Imaging (MRI) findings of common and uncommon pathologies causing a locked knee.
- To highlight less frequent causes of mechanical knee blockage for improved diagnostic accuracy.
Main Methods:
- Review of relevant literature and illustrative cases.
- Focus on MR imaging features of internal derangements, loose bodies, and specific ligament/synovial lesions.
Main Results:
- Bucket handle tears of the menisci are the predominant cause of locked knee.
- Other significant causes include traumatic/degenerative loose bodies, cruciate ligament cysts, and pigmented villonodular synovitis.
- Non-specific kinematic interference often accompanies meniscal tears, necessitating a broader diagnostic approach.
Conclusions:
- MRI is crucial for diagnosing the diverse etiologies of a locked knee.
- Recognizing less common abnormalities is vital for identifying mechanical blocks to knee extension.
- Comprehensive MR evaluation aids in differentiating various causes of knee locking beyond meniscal pathology.