Doctor123.org

Knee Injuries: ACL, PCL, MCL, Meniscus, Emergency Medicine

Basics

Description

- ACL: - Most commonly injured knee ligament - 200,000 ACL injuries annually in US - 2/3 of all ACL injuries are noncontact - Female gender: 3 greater risk

- Medial meniscus injury: - Patient may recall the knee "giving way " - Inability to fully extend knee is common - Effusion is found in 50% and usually occurs over 6 " 12 hr. - Pain is often intermittent and localized to the joint line - Unlike ligamentous injury, patients often report completion of activities at time of injury - Degenerative meniscal tears tend to have a more insidious, atraumatic presentation, with mild swelling, vague joint line pain, and sometimes with mechanical symptoms. Often associated with osteoarthritis.

- Stress testing: Always compare the injured to the uninjured side (asymmetry is more reliable than absolute degree of laxity): - Pain and spasm can limit the utility of all stress testing in the acute phase - Lachman test is most reliable for ACL: - Knee flexed 20 °, patient supine with thigh supported and hip slightly externally rotated. Quickly bring the tibia forward on the femur, 1 hand holding proximal tibia, the other stabilizing the femur just above the patella, evaluating for quality of the endpoint and degree of anterior translation of the tibia - Pain with motion = partial tear or disruption - Quantification of degree of movement less important then simply positive or negative interpretation of test

- Quadriceps active test (PCL): - Patient supine, knee flexed at 90 °, hip flexed at 45 ° - Patient attempts to extend knee against examiners counterforce - Positive if the tibia translates anteriorly during quad activation

- Standard radiography: - Obtain on all suspected ACL injuries due to high risk of fractures - Important in children to evaluate for tibial spine and growth plate fractures - Views: AP, lateral, oblique, notch - Special attention to avulsion fractures of the medial/lateral tibial spine and lateral tibial plateau, which can be seen with ACL/PCL injuries and may be more likely to be treated operatively - Fat " fluid level for fracture.

- Treatment (if no fracture): - Rest, Ice, Compression, Elevation - Weight Bearing as Tolerated, crutches for comfort if needed - May provide knee immobilization for protection, but encourage motion out of brace as much as possible, especially if follow-up may be delayed

  • Cruciate ligament injuries:Anterior cruciate ligament (ACL):From the posteromedial aspect of the lateral femoral condyle to the intraspinus area on the tibiaPrevents excessive anterior translation of the tibia, internal rotation of the tibia on the femur, or hyperextension of the knee.Posterior cruciate ligament (PCL):Twice as strong and twice as thick as the normal ACL, less commonly injuredFrom anterolateral aspect of medial femoral condyle to the posterior tibia
  • Meniscal tears:Medial meniscus injury most commonMore firmly attached to the joint capsule and less mobile than lateral meniscusTears are the result of tensile or compressive forces between the femoral and tibial condylesExtension of meniscal tear may result in a free segment that may become displaced into the joint, resulting in a true locked joint.
  • Medial collateral ligament:From the posterior aspect of medial femoral condyle to the tibia, distal to jointOften accompanied by other injury:Hyperextension with external rotation (ACL/PCL injured 1st)Anterior stress (ACL injured 1st)

Epidemiology

Incidence and Prevalence Estimates

  • ACL:Most commonly injured knee ligament200,000 ACL injuries annually in US2/3 of all ACL injuries are noncontactFemale gender: 3 greater risk
  • Associated injuries: ’ Ό50% ACL injuries are associated with meniscal tearsACL injuries commonly have chondral and subchondral injuries
  • Meniscus:Medial meniscus injury 10 more common than lateralTrue locked joint in only 30%

Etiology

  • Cruciate ligament injuries:ACL: Often deceleration with flexion and rotation, or hyperextensionUsually sports-related, especially skiing and footballPlant-and-pivot or stop-and-jump mechanismPCL: "Dashboard injury " : Flexed knee with posteriorly directed force to the anterior proximal tibia (motor vehicle crash or direct trauma)Fall on flexed knee
  • Meniscus Injury:Sudden rotary motion of knee associated with squatting, pivoting, turning, and bendingCommon in sports with low stance positions (wrestling/football) or kneeling position (carpet installers, plumbers)
  • Medial collateral ligament injuries:Direct trauma to lateral kneeMost common: Valgus stress with external rotation on flexed knee:From catching a ski tipSide tackle (football)
  • The ACL is the most frequently injured knee ligament in children.
  • Isolated MCL injury infrequent before growth plate closure (<14-yr old)

Diagnosis

Signs and Symptoms

History

  • Cruciate ligament injuries:Feeling knee "give way, " pop, tearing sensationMost patients report immediate knee dysfunction, but some may ambulate despite complete ACL rupture because of stability from supporting structures.Large, almost immediate effusion " patients report significant swelling
  • Medial collateral ligament:Tearing sensation and immediate pain in medial aspect of kneeMedial pain and tenderness may be more pronounced with partial tears than with complete tears.
  • Medial meniscus injury:Patient may recall the knee "giving way "Inability to fully extend knee is commonEffusion is found in 50% and usually occurs over 6 " 12 hr.Pain is often intermittent and localized to the joint lineUnlike ligamentous injury, patients often report completion of activities at time of injuryDegenerative meniscal tears tend to have a more insidious, atraumatic presentation, with mild swelling, vague joint line pain, and sometimes with mechanical symptoms. Often associated with osteoarthritis.

Physical Exam

  • Ability to bear weight reduced with all injuries
  • Palpate for pain on:bony prominences for fracturegrowth plates in childrenmedial and lateral joint line (meniscus and collateral ligament injury)
  • Range of motion:Locking: May occur with ACL (interposition of torn cruciate), meniscus injury, loose body (arthritis)Pseudolocking may be present from pain, effusion, or spasm
  • Effusion:Immediate (within 2 " 3 hr) usually indicates a significant intra-articular injury including ACLAbout 70% of acute knee hemarthroses are caused by ACL injury, but lack of effusion does not rule out ACL injuryMCL, meniscus, PCL injuries have more delayed effusion (12 " 24 hr)Warmth, erythema: Consider infection
  • Neurovascular exam:Distal pulses1st dorsal web-space sensation (deep peroneal nerve)Ankle/toe dorsiflexion
  • Stress testing: Always compare the injured to the uninjured side (asymmetry is more reliable than absolute degree of laxity):Pain and spasm can limit the utility of all stress testing in the acute phaseLachman test is most reliable for ACL:Knee flexed 20 °, patient supine with thigh supported and hip slightly externally rotated. Quickly bring the tibia forward on the femur, 1 hand holding proximal tibia, the other stabilizing the femur just above the patella, evaluating for quality of the endpoint and degree of anterior translation of the tibiaPain with motion = partial tear or disruptionQuantification of degree of movement less important then simply positive or negative interpretation of testPivot shift test: More specific for ACL injury but unreliable without anesthesia and painful acutely. Not recommended routinely in the ED.Anterior/posterior drawer sign:Knee flexed 90 °, patient supine, hip flexed 45 °, foot neutral and stabilized (sit on foot)Observe for posterior sag of tibia, positive with PCL injuryPosterior drawer (PCL): Movement of tibia back with application of posterior pressureAnterior drawer (ACL): Movement of tibia forward with anterior distraction forceQuadriceps active test (PCL):Patient supine, knee flexed at 90 °, hip flexed at 45 °Patient attempts to extend knee against examiners counterforcePositive if the tibia translates anteriorly during quad activationVarus/valgus stress testing: Evaluate in extension and 20 ° flexion for MCL and LCL laxity
  • Meniscus: Wait until acute pain is controlled:McMurray: While palpating joint lines, extend the knee while internally and then externally rotating. Pain and click is positive.Apley: With patient prone, flex knee to 90 °, provide axial load and internally/externally rotate lower leg. Pain is positive.
  • Children and adolescents show more laxity on exam than adults
  • Examine hip and obtain radiograph if any concern for hip pathology (especially slipped capital femoral epiphysis)
  • Have a high suspicion for epiphyseal growth plate injuries

Diagnosis Tests & Interpretation

Lab

  • If cause of knee effusion not clearly traumatic, synovial aspirate can be sent for cell count, Gram stain, culture, crystals
  • Arthrocentesis is usually not indicated after trauma except to relieve symptoms from tense effusion

Imaging

  • Ottawa knee rules (adults): Plain films required for patients with any of 5 findings:Age ≥55Isolated tenderness of patellaTenderness at head of fibulaInability to flex 90 °Inability to bear weight both immediately and in ED (4 steps)
  • Standard radiography:Obtain on all suspected ACL injuries due to high risk of fracturesImportant in children to evaluate for tibial spine and growth plate fracturesViews: AP, lateral, oblique, notchSpecial attention to avulsion fractures of the medial/lateral tibial spine and lateral tibial plateau, which can be seen with ACL/PCL injuries and may be more likely to be treated operativelyFat " fluid level for fracture.
  • MRI is around 95% sensitive for ACL tears and other intra-articular disorders (menisci, PCL, osteonecrosis, osteochondral lesions, occult fractures) and even more specific, but it is rarely indicated emergently.
  • Arteriograms to evaluate vascular integrity for suspected dislocations
  • US useful to diagnose cysts and popliteal artery aneurysms

Ottawa knee rules do not apply to children.

Essential Workup

  • Neurovascular evaluation
  • Exclusion of fractures and infection
  • Evaluate for multidirectional instability
  • Valgus/varus stress at 20 ° of flexion
  • Extensor mechanism function
  • Lachman test for ACL injury

Differential Diagnosis

  • Growth plate injury
  • Tibial plateau bony injury, other fracture
  • Transient knee dislocation
  • Transient patellar dislocation
  • Hip injury causing referred pain
  • Nontraumatic causes of knee effusion and pain including septic joint, gout, osteoarthritis, rheumatoid arthritis

Treatment

Initial Stabilization/Therapy

  • ABC 's, ATLS
  • Immobilize knee
  • Document neurovascular function
  • Apply ice, elevate, analgesia

Ed Treatment/Procedures

  • Reduce locked knee from meniscus injury within 1st 24 hr after injury:With patient seated, hang extremity off edge of exam table at 90 °: This with analgesia alone may reduce locked joint.Assist with applying gentle traction and rotation of tibia
  • Arthrocentesis may afford relief with large effusions and assist in reducing locked joint:Follow with compressive dressing
  • Treatment (if no fracture):Rest, Ice, Compression, ElevationWeight Bearing as Tolerated, crutches for comfort if neededMay provide knee immobilization for protection, but encourage motion out of brace as much as possible, especially if follow-up may be delayed

Medication

  • Pain control: NSAIDs preferred over opioids
  • Ibuprofen: 400 " 600 mg (peds: 5 " 10 mg/kg) PO QID.

Follow-Up

Disposition

Admission Criteria

  • Isolated ACL, PCL, meniscus, or collateral ligament injury rarely requires emergent hospitalization
  • Low threshold to admit possible knee dislocations for monitoring
  • Fractures often need ORIF to limit post-traumatic arthritis

Discharge Criteria

Most patients can be managed as outpatients with appropriate referral.

Issues for Referral

  • Re-exam is recommended at 48 hr if ED exam is inconclusive or if history suggests more significant injury than initial exam demonstrates (i.e., severe symptoms, hearing "pop " ).
  • Orthopedic referral within 1 " 2 wk if significant ligamentous injury is present.
  • Surgical repair of all lesions may be considered for patients wishing to return to sports or active lifestyles.

Pearls and Pitfalls

  • Do a careful neurovascular exam, and always examine 1 joint above and below the pain for associated injury or referred pain
  • Have a high index of suspicion for a reduced total knee dislocation if patient has multidirectional knee instability or injuries to multiple ligaments
  • Do not miss: Knee dislocation, fractures, septic joint, referred pain from hip, neurovascular injury

Additional Reading

  • Chen L, Kim PD, Ahmad CS, et al. Medial collateral ligament injuries of the knee: Current treatment concepts. Curr Rev Musculoskelet Med. 2008;1(2):108 " 113.
  • Meuffels DE, Poldervaart MD, Diercks RL, et al. Guideline on anterior cruciate ligament injury: A multidisciplinary review by the Dutch Orthopaedic Association. Acta Orthop. 2012;83(4):379 " 869.
  • Noyes FR. Noyes ' Knee Disorders: Surgery, Rehabilitation, Clinical Outcomes. Philadelphia, PA: Saunders-Elsevier; 2010.
  • Ryzewicz M, Peterson B, Siparsky PN, et al. The diagnosis of meniscus tears: The role of MRI and clinical examination. Clin Orthop Relat Res. 2007;455:123 " 133.

Codes

ICD9

  • 836.0 Tear of medial cartilage or meniscus of knee, current
  • 844.1 Sprain of medial collateral ligament of knee
  • 844.2 Sprain of cruciate ligament of knee
  • 844.0 Sprain of lateral collateral ligament of knee

ICD10

  • S83.419A Sprain of medial collateral ligament of unsp knee, init
  • S83.519A Sprain of anterior cruciate ligament of unsp knee, init
  • S83.529A Sprain of posterior cruciate ligament of unsp knee, init
  • S83.249A Oth tear of medial meniscus, current injury, unsp knee, init
  • S83.409A Sprain of unsp collateral ligament of unsp knee, init encntr
  • S83.509A Sprain of unsp cruciate ligament of unsp knee, init encntr

SNOMED

  • 444470001 Injury of anterior cruciate ligament
  • 433162006 injury of posterior cruciate ligament (disorder)
  • 444448004 Injury of medial collateral ligament of knee (disorder)
  • 302932006 Tear of medial meniscus of knee
  • 239725005 Rupture of anterior cruciate ligament (disorder)
  • 239727002 Rupture of posterior cruciate ligament (disorder)