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Knee Problems

I. Introduction

A. Injuries by tissue types

1. Ligament injuries

a. Traumatic sprains

2. Meniscus (fibrocartilage):

a. Traumatic tears

b. Degenerative tears

3. Articular surface (hyaline cartilage):

a. Traumatic chondrosis

b. Degenerative chondrosis

4. Tendon

a. Traumatic rupture

b. Degenerative tendinosis (tendinitis)

II. Anterior cruciate ligament (ACL) tears

A. Incidence

1. Most common disabling injury of knee

2. Nationwide: 250,000 injuries per year, 1/1500 knee injuries

3. 70% sports-related

B. Common injury mechanisms

1. Contact or non-contact.

2. Deceleration-rotation

3. Hyperextension

4. Valgus or varus force

a. Combined with collateral ligament damage

C. History

1. Acute tear

a. Felt or heard "pop," "tearing"

b. Knee gave out during change of direction or landing from jump

c. Swelling within 12E

d. "Two-Fisted" sign

2. Chronic deficiency

a. Knee "gives way" during change of direction or while landing from jump

b. Knee feels "unstable," "loose" or "separates"

1) "Two-fisted sign

c. History of previous knee "sprain"

d. Other symptoms reflect associated injuries

1) meniscus tear - pain, aching, popping or swelling

2) articular cartilage injury - pain or swelling

D. Physical findings

1. Effusion, limited flexion.

2. Flexion contracture, limited extension.

3. Lachman's test: best test

a. Anterior drawer at 30E flexion.

b. Isolates ACL, neutralizes hamstrings.

4. Anterior drawer test

a. Difficult to perform in acute situation but occasionally helpful

5. Pivot shift test

a. Most helpful after acute swelling and pain has subsided.

b. Thought to correlate with "giving out" episodes

6. Common associated injuries

a. Meniscus tears

b. MCL sprains

c. Bone bruises

E. Diagnostic studies

1. X-rays: usually normal

a. Segond's sign: post-lat capsular avulsion fx. Uncommon, but pathognomonic for ACL tear

b. Tibial spine avulsion

2. MRI 90% accuracy rate for complete tears.

a. Most valuable for detecting associated meniscus tears.

b. Reveals "bone bruises" in most (significance uncertain)

F. Differential diagnosis

1. ACL Tears

2. Meniscal Tears

3. Other ligament injuries

4. Patella Dislocation

5. Osteo-chondral fractures

G. Treatment

1. Acute

a. R-I-C-E, crutches/splint pm

b. Weight-bearing as tolerated (WBAT) unless locked knee (displaced meniscus tear) suspected.

c. Early motion

d. NSAIDS X 7 - 10 days

2. Chronic

a. Same as above following recent giving way episode

b. Check carefully for meniscus tears - very common

H. Referral

1. All suspected ACL tears upon diagnosis: an acutely swollen knee following a giving way episode, twisting, or hyperextension injury should be considered an ACL tear until proven otherwise.

III. Posterior cruciate ligament (PCL) tears

A. General considerations

1. Strongest and largest knee lig.

2. Injuries uncommon

B. Common mechanisms of injury

1. Ant. blow to flexed knee, below patella

a. Sports

b. Dashboard injury

2. Fall on knee with foot plantar flexed

3. Hyperflexion

C. History

1. Swelling

2. Post. knee pain

3. Minimum instability with isolated PCL tear

4. "Something doesn't feel right"

D. Physical findings

1. (+) post drawer test

2. (+) quad-active test

3. (+) tibial sag or drop back

4. Effusion

E. Diagnostic studies

1. X-rays: normal, unless bony avulsion

2. MRI

a. Usually diagnostic acutely

b. In chronic case, ligament may appear "reconstituted"

F. Treatment: controversial

1. Avulsion fractures: surgery

2. Isolated PCL injury: conservative

3. Combined injury with other ligaments instability: surgical in most patients, depending upon age and activity level.

G. Referral: upon diagnosis, or suspected injury

IV. Collateral ligament sprains - medial and lateral

A. General considerations

1. Medial (MCL)

a. Primary restraint to valgus force.

b. Very common injury

c. Good healing potential

2. Lateral (LCL)

a. Resists varus force

b. Uncommon injury

c. More likely (than MCL) to require surgical treatment because of associated injuries.

B. History

1. Valgues blow (MCL). Varus blow (LCL)

2. "Pop"

3. Medial swelling (localized)

4. Feeling of joint opening with lateral movement

C. Physical findings

1. Medial

a. Tender along course of MCL

b. Increased valgus laxity in more severe injuries

c. Often associated with ACL tears

2. Lateral

a. Tender along course of LCL

b. Increased varus laxity in more severe injuries

c. More sever injuries frequently associated with postuolateral laxity and cruciate ligament injury.

D. Grades

1. Grade I: Microscopic injury: Tenderness, but no increased laxity

2. Grade II: Partial macroscopic tear: Increased laxity, with endpoint which is painful

3. Grade III: Complete tear: grossly increased laxity, no endpoint (less pain on stress).

E. Diagnostic studies

1. X-rays: usually normal, occasionally show femoral avulsion

2. MRI: usually diagnostic, but not indicated unless diagnosis is uncertain or cruciate tear is suspected

F. Differential diagnosis

1. Medial soft tissue/bony contusion

2. Patellar subluxation

3. Medial or lateral meniscal tear

4. Associated cruciate ligament tear

G. Treatment

1. R-I-C-E, NSAIDs

2. Hinged knee brace


4. Early rehabilitation

H. Referral

1. Assoc. injury (ACL or PCL)

2. Failure of treatment

V. Meniscus tears

A. Incidence

1. Most common referred knee injury in USA (1/1000)

2. High association with ACL tears (50% incidence)

3. Almost always tears in posterior portion (=posterior horn")

4. 2 types - traumatic and degenerative

B. Anatomy and function

1. Increase contact area between femur and tibia

2. Distribute pressure across larger area of articular cartilage

3. Check secondary stabilizers

C. Common mechanisms of injury

1. Twisting on flexed, loaded knee

2. Hyperflexion

3. In middle aged, minimal or no trauma maybe recalled due to gradual attrition over time.

D. History

1. Joint line pain (medial more common than lateral)

2. Catching, popping, locking, swelling, stiffness

E. Physical findings

1. Joint line tenderness (mid to posterior)

2. Effusion (valuable)

3. Pain with passive flexion

4. Pain with manipulative tests (McMurray, Apiey)

5. In locked knee, loss of extension, tenderness at anterior joint line, pain to passive extension

F. Diagnostic studies

1. X-rays: normal

a. Joint space narrowing suggest arthritis present

2. MRI study of choice, usually diagnostic

a. Medial - 90 - 98% sensitive and specific

b. Lateral - 70 - 80% sensitive and specific

3. Arthrogram: replaced by MRI

G. Differential diagnosis

1. Articular cartilage injury

2. Degenerative arthritis

3. Patellofemoral chondrosis

4. Osteochondritis dissecans

5. Loose body

H. Treatment

1. R-I-C-E, NSAIDs: no sports

2. Crutches for locked knee, NWB, otherwise WBAT

3. Some degenerative tears will become asymptomatic with time and NSAIDS

4. Traumatic tears usually require surgery.

I. Referral

1. Upon diagnosis or suspicion of traumatic tears

2. Failure of degenerative tears to respond to conservative treatment.

J. Surgery

1. Arthroscopic repair or partial resection