Anterior Cruciate Ligament (ACL) Injury - Orthopedics

Snapshot
- A 21-year-old man presents to the emergency department for severe pain in the right knee. A few hours prior to presentation, an opposing football player hits his leg from his right side. Afterwards, he felt a "pop" sound that was followed by severe knee pain and a sensation of knee instability. On physical exam, there is anterior translation of the proximal tibia when pulled as the patient has the knee flexed at 90° and supine. Ice is applied to the knee and ibuprofen is prescribed. Orthopedic surgery is consulted to evaluate if ligamental reconstruction is needed.

Introduction
- Clinical definition
  - injury in the form of tear or rupture affecting the anterior cruciate ligament (ACL) in the knee
- Associated conditions
  - unhappy triad which consists of injury to the
    
    ACL
    
    medial collateral ligament
    
    medial meniscus

Prognosis
- The majority of athletes are able to return to their sports activities with ACL reconstruction

Epidemiology
- Incidence
  - non-contact ACL injuries are more common
- Demographics
  - more common in female athletes
- Risk factors
  - sports (e.g., football, soccer, skiers, and basketball)
  - motor vehicle accidents

ETIOLOGY
- Pathoanatomy
  - Pathology
    
    contact mechanisms
    
    injury that causes hyperextension or valgus deformation of the knee
    
    e.g., football injury
    
    high-speed motor vehicle accident
    
    non-contact mechanisms
    
    changing direction, pivoting, or landing that leads to rotation or valgus stress of the knee after sudden deceleration
  - Normal anatomy
    
    the ACL course
    
    originates in the posteromedial aspect of the lateral femoral condyle
    
    reaches the anteromedial aspect of the tibia
    
    the ACL plays an important role in knee stability
    
    it controls anterior translation of the tibia
    
    it also restrains against tibial rotation, varus, and valgus stress

Presentation
- Symptoms
  - feeling a "pop" in the knee
    
    thereafter, there is acute swelling and pain
  - instability or "giving out" knee
- Physical exam
  - anterior drawer test
    
    the proximal tibia is anteriorly pulled while the patient is supine and the knee is flexed at 90 degrees
    
    if there is anterior translation then the test is positive
  - Lachman test
    
    the proximal tibia is anteriorly pulled with one hand, while the other hand stabilizes the distal femur while the knee is flexed at 30 degrees
  - hemarthrosis

Imaging
- Magnetic resonance imaging (MRI)
  - indication
    
    an imaging modality that can confirm the diagnosis
    
    if reconstruction is a possibility or to identify concomitant knee pathology

Studies
- Making the diagnosis
  - can be made based on typical clinical presentation alone
  - can be confirmed by MRI or knee arthroscopy

Differential
- Meniscal tear
  - differentiating factor
    
    patients can have a positive
    
    Thessaly test
    
    McMurray test
    
    Apley test
- Posterior collateral ligament (PCL) injury
  - differentiating factor
    
    patients can have a positive posterior drawer test

Treatment
- Conservative
  - rest, ice, compression, and elevation (RICE) therapy
    
    indication
    
    management to reduce pain, edema, and hemarthrosis in the acute stage of the injury
    
    nonsteroidal anti-inflammatory drugs are typically added
- Operative
  - surgical reconstruction
    
    indications
    
    performed in
    
    young and active patients with high demand sports or jobs
    
    significant knee instability
    
    such as injuries affecting multiple knee structures (e.g., unhappy triad)

Complications
- Osteoarthritis
- Arthrosis
- Sports disability

Action	Numeric Key	Letter Key	Function Key
Show Bullets		S	Enter (frontside only)
20%	1	N
40%	2	H
60%	3	F	Enter (backside only)
80%	4	E
100%	5	M
Toss	0	T

(M2.OR.17.4799) A 25-year-old male presents to his primary care physician for pain in his knee. The patient was in a wrestling match when his legs were grabbed from behind and he was taken to the floor. The patient states that the moment this impact happened, he felt a snapping and sudden pain in his knee. When the match ended and he stood back up, his knee felt unstable. Minutes later, his knee was swollen and painful. Since then, the patient claims that he has felt unstable bearing weight on the leg. The patient has no significant past medical history, and is currently taking a multivitamin and protein supplements. On physical exam you note a tender right knee, with erythema and an effusion. Which of the following is the most likely physical exam finding in this patient?

QID: 109202

Type & Select Correct Answer

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Laxity to valgus stress

(0/4)

Laxity to varus stress

(0/4)

Clicking and locking of the joint with motion

25%

(1/4)

Anterior translation of the tibia relative to the femur

25%

(1/4)

Posterior translation of the tibia relative to the femur

25%

(1/4)

Select Answer to see Preferred Response

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