High Yield Topics

Posterolateral Capsular Tear

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Ovid: 5-Minute Sports Medicine Consult, The


Posterolateral Capsular Tear
Matt Roth
Jacklyn Kiefer
Basics
Description
  • Posterolateral corner (PLC) of the knee is composed of the posterior lateral capsule and its supporting structures.
  • The supporting structures of the PLC are composed of the popliteus muscle/tendon complex, the popliteofibular ligament, the lateral collateral ligament complex, and the arcuate-fabellofibular ligament complex.
  • Biomechanically, the PLC is a primary restraint to both varus motion and external rotation of the tibia, and helps to resist posterior translation (1)[C].
  • When some or all of these structures are damaged, a pathologic laxity occurs that can result in varus and rotational instability and chronically can lead to post-traumatic arthritis (1)[C].
  • Grading system:
    • Address both varus opening and rotational instability compared to unaffected side
    • Grade I: Posterolateral pain, varus opening/break 0–5 mm, 0–5 degrees of laxity on dial test
    • Grade II: Varus opening 6–10 mm, 6–10 degrees of laxity on dial test
    • Grade III: Varus opening >10 mm, >10 degrees of laxity on dial test
Epidemiology
  • Isolated PLC injuries are uncommon (<2% of all acute ligamentous knee injuries).
  • May occur in conjunction with cruciate or lateral collateral ligament injury or any multiligamentous knee injury
  • High association of chronic PLC insufficiency in the setting of failed cruciate ligament reconstruction and/or chronic instability
Risk Factors
Any collision sport or recreational activity where running and cutting may cause an anteromedially directed blow or a noncontact hyperextension with external twisting of the knee
Etiology
Various mechanisms of injury can occur:
  • Posterolateral directed blow onto a nearly fully extended tibia, which results in knee hyperextension
  • Noncontact hyperextension with an external rotation twisting injury
  • A posterior directed blow to the proximal tibia of a flexed knee (dashboard injury)
  • Complete knee dislocation from varus force with hyperextension
Commonly Associated Conditions
  • Posterior cruciate ligament (PCL) tear
  • Anterior cruciate ligament (ACL) tear
  • Tibial plateau fracture or contusion
  • Lateral collateral ligament (LCL) ligament injury
  • Peroneal nerve injury (as high as 30%)
Diagnosis
History
  • Mechanism of injury
  • Acutely, pain and swelling to posterolateral knee
  • Feelings of knee instability, hyperextension, or knee “giving out”
  • Difficulty with twisting, pivoting, or cutting
  • Pain with kneeling
  • History of cruciate repair failure
Physical Exam
  • Assess for effusion.
  • Assess the vascular status of the leg and foot. Diminished pulses may indicate a vascular injury and warrant an arteriogram (2)[C].
  • Assess neurologic status of leg and foot, particularly the common peroneal nerve and its branches (weakened ankle dorsiflexion and great toe extension or diminished dorsal foot sensation).
  • Assess alignment and gait. Inspection in standing position may reveal asymmetrical varus involvement on the affected side. In chronic injury, varus thrust ambulatory pattern or ambulation with flexed knee (1)[C].
  • Perform a complete ligamentous examination:
    • Cruciate and collateral ligaments must be evaluated to rule out a multiple ligamentous injury (2)[C].
    • Test anterior and posterior translation with the knee in 30 degrees of flexion (Lachman examination) and 90 degrees of flexion (drawer test).
    • Test varus and valgus laxity with the knee fully extended at 30 degrees of flexion. Laxity with full extension suggests PLC injury (3)[C]
  • Specialty testing of the PLC:
    • Dial test or posterolateral rotation test most helpful (1)[C]:
      • With the patient in the supine position, the foot is passively externally rotated and the degree of rotation, measured by thigh-foot angle, is compared to the contralateral limb.
      • Test should be performed with the knee in both 30 and 90 degrees of flexion.
      • >10-degree increase in external rotation with the affected knee in 30 degrees of flexion represents a pathologic state.
      • If improvement occurs with 90 degrees of flexion, suggestive of isolated PLC injury (no PCL involvement)
    • External rotation recurvatum test:
      • Lift great toe while stabilizing thigh, looking for increased recurvatum compared to unaffected knee.
    • Posterolateral drawer test:
      • Knee flexed 80 degrees, foot stabilized in 15 degrees of external rotation, looking for increased translation when posterior force applied to tibia (2)[C]
    • Reverse pivot shift test addresses tibial plateau subluxation:
      • With the patient supine, knee flexed, and foot externally rotated 45–60 degrees.
      • Valgus force applied as knee extended
      • Visible shift or clunk near 30 degrees of flexion implies reduction of the subluxation.
      • If PLC is insufficient, the lateral tibial plateau will be subluxed posteriorly relative to the lateral femoral condyle (1)[C].
Diagnostic Tests & Interpretation
Imaging
  • Plain radiographs: Minimum of anteroposterior and lateral to rule out associated fractures (1)[C]:
    • Segond sign (see ACL Injury), avulsion fracture of the fibular head or styloid, or tibial plateau fracture may be associated with injury to posterolateral structures (1)[C].
  • Low threshold for MRI in case of suspected PLC injury:
    • Higher-powered magnets (1.5 T or greater) helpful for viewing variable structures of PLC (1)[C]
    • Injuries to 2 or more structures of PLC (especially popliteus complex, LCL, or postererolateral capsule) strongly suggests PLC insufficiency (4)[C].
    • Thin-slice coronal oblique view through fibular head and styloid may improve PLC structure visibility (4)[B].
  • US may be an emerging tool for evaluating posterolateral corner structures (5)[C].

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Differential Diagnosis
  • Posterior cruciate ligament injury
  • ACL injury
  • Lateral collateral ligament complex injury
  • Knee dislocation
  • Tibial plateau fracture
Treatment
  • Acute treatment:
    • Recognize that a serious knee injury has occurred.
    • Treatment depends on degree of laxity or instability, timing from injury, and concomitant ligament involvement (2)[C].
    • Acute PLC injuries are amenable to surgical repair if treated early. Surgical options for treatment include primary repair, advancement, or reconstruction (2)[C].
  • Immobilization with pain and swelling control comprise initial treatment.
  • Grade I injuries:
    • No abnormal motion or instability.
    • Nonoperative treatment results in good functional outcomes (2)[B].
    • Hinged knee brace locked in extension for 2–4 wks with protected weight-bearing for the 1st 2 wks (3)[C]
    • Followed by progressive range of motion and rehabilitation program. Closed chain exercises (2) initiated at 6–8 wks (3)[C].
    • Gradual progression as strength improves. Full release to activities anticipated at 12–14 wks (3)[C].
  • Grade II injuries:
    • Mild to moderate abnormal joint motion
    • Nonoperative or surgical treatment, depending on associated injuries (2)[C]
    • Isolated injury can be treated like grade I injuries with prolonged protected weightbearing (2)[C]:
      • Residual laxity may persist with nonoperative treatment (1)[C].
      • Unrestricted return to full activity may take up to 3–4 mos for nonoperative cases (3)[C].
    • More significant injuries or those associated with cruciate injury should be fixed surgically (2)[C]:
      • Primary repair may be possible if surgery performed within 3 wks of injury (2)[C].
      • Delayed treatment requires anatomic reconstruction and addressing malalignment issues (2)[C].
  • Grade III injuries:
    • Requires operative intervention to prevent long-term instability and expedited development of osteoarthritis (6)[C]
    • Early on, primary repair may be possible depending on quality of injured structures (2)[C].
    • After 4–6 wks, reconstruction necessary because of associated scarring (3)[C]
    • Return to unrestricted sports participation usually 10–12 mos post surgical repair (1)[C]
  • Chronic posterolateral rotatory instability:
    • Management of chronic PLC instability is more difficult than an acute PLC (injury) (1)[C].
    • Primary repair of structures usually is impossible (2)[C].
    • Assessment of both gait and lower extremity alignment is important (1)[C].
    • Patient with preexisting varus malalignment and varus thrust during gait may not have a successful reconstruction because the lateral structures may be attenuated and nonfunctional (1)[C].
    • In this setting, proximal tibial osteotomy may be indicated before ligamentous reconstruction. The most critical structures to reconstruct are the popliteofibular ligament, popliteus, and LCL (1)[C].
    • A variety of surgical procedures described without consensus or evidence-based outcomes (4)[C]
    • Recreating damaged structures favored over nonanatomical reconstructions (1)[C]
Additional Treatment
Additional Therapies
  • Rehabilitation emphasis on quadriceps strengthening (1)[C]
  • Early immobilization should not preclude protected strengthening. Best results are achieved with early intervention (1)[C].
  • Progressive resistance exercises and sports-specific drills initiated as range of motion advanced (2)[C]
  • Patients who develop excessive knee hyperextension or varus thrust during gait may benefit from gait retraining before reconstruction (7)[C].
Ongoing Care
Complications
  • Peroneal nerve dysfunction secondary to primary injury or surgery (1)[C]
  • Residual laxity, persistent pain, or osteoarthritis may occur even with surgical intervention (1)[C].
References
1. Ranawat A, Baker CL, Henry S, et al. Posterolateral corner injury of the knee: evaluation and management. J Am Acad Orthop Surg. 2008;16:506–518.
2. Ricchetti ET, Sennett BJ, Huffman GR. Acute and chronic management of posterolateral corner injuries of the knee. Orthopedics. 2008;31:479–488; quiz 489–490.
3. Cooper JM, McAndrews PT, LaPrade RF. Posterolateral corner injuries of the knee: anatomy, diagnosis, and treatment. Sports Med Arthrosc. 2006;14:213–220.
4. Vinson EN, Major NM, Helms CA. The postero-lateral corner of the knee. AJR Am J Roentgenol. 2008;190:449–458.
5. Barker RP, Lee JC, Healy JC. Normal sonographic anatomy of the posterolateral corner of the knee. AJR Am J Roentgenol. 2009;192:73–79.
6. Kannus P. Nonoperative treatment of grade II and III sprains of the lateral ligament compartment of the knee. Am J Sports Med. 1989;17:83–88.
7. Covey DC. Injuries of the posterolateral corner of the knee. J Bone Joint Surg Am. 2001;83-A:106–118.
Additional Reading
Malone AA, Dowd GS, Saifuddin A. Injuries of the posterior cruciate ligament and posterolateral corner of the knee. Injury. 2006;37:485–501.
Codes
ICD9
  • 844.0 Sprain of lateral collateral ligament of knee
  • 844.2 Sprain of cruciate ligament of knee
  • 844.8 Sprain of other specified sites of knee and leg
Clinical Pearls
  • Appropriate management depends on injury severity and timing of diagnosis.
  • Significant posterolateral capsular and PLC injuries causing varus and rotational instability require expedited evaluation and treatment, as surgery is ideally performed within 3 wks from injury onset.
  • Isolated PLC injuries are rare, and concomitant cruciate and bony injuries must be ruled out.
  • Chronic injuries associated with feeling of instability or hyperextension and can cause abnormal gait and expedited medial osteoarthritis.
  • Diagnosis and treatment of this injury continue to evolve.


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