Fact-sheet: Fibular collateral ligament tear
Updated on 09/09/2019 at 1:39 PM
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Definition
Lateral collateral ligament injury rarely occurs without involvement of the PLC.
Less common than injury to the medial ligamentous complex.
Lateral ligamentous complex composed of three layers:
- Superficial: iliotibial tract and biceps femoris muscle.
- Intermediate: patellar retinaculum and meniscopatellar + patellofemoral ligaments.
- Deep: PLC.
PLC = stability.
3 main components: LCL/popliteus tendon/popliteofibular ligament.
Clinical features
Mechanism of injury:
- sudden hyperextension
- varus stress on an extended knee
- injury with lateral rotation, twisting
Associated lesions are common (particularly of the central pivot)
In the acute setting: posterolateral knee pain and functional impairment.
In the chronic setting: knee instability, particularly in varus, with secondarily associated lesions
Laboratory findings
Unaffected
Radiography
In the acute setting, look for:
- A fracture of the fibular tip (arcuate sign), a larger fragment indicating a biceps femoris avulsion
- An avulsion fracture of the lateral border of the femoral condyle (proximal insertion of the lateral collateral ligament)
- Avulsion fracture of the iliotibial band
- Segond fracture (insertion of the ALL)
At a distance from the trauma, stress radiographs may be obtained, showing widening of the lateral femorotibial joint space.
Ultrasound
Study with the knee slightly flexed
LCL = hypoechoic band under physiological conditions
Partial tear = heterogeneous thickening with soft tissue infiltration.
Complete tear = fiber discontinuity or bony avulsion
Search for bony avulsion.
Look for common fibular nerve injury
CT
Assessment of bony avulsions
MRI
Reference examination for PLC injuries. Not all PLC structures are clearly identifiable under physiological conditions.
Direct signs = ligament signal abnormality:- Grade I = peri-ligamentous infiltration- Grade II = partial tear (focal disruption of a few fibers)- Grade III = complete tear with discontinuity, most often distal, or bony avulsion
Indirect signs:- Bone marrow edema of the fibular apex- Contrecoup bone contusion of the medial femoral condyle- Avulsion or injury of the biceps femoris myotendinous junction- Popliteus muscle involvement- Posterolateral capsular involvement- Associated meniscal and central pivot lesions
Management
Orthopedic or surgical management of the posterolateral corner and associated lesions
Differential diagnosis
Do not overlook PLC injury, which can lead to chronic knee instability.