Knee

Question 1

DDx locking, instability, swelling of the knee

Answer 1

Torn meniscus/loose body in joint

Question 2

DDx psudo-locking (limited ROM without mechanical block) in the knee

Answer 2

Effusion

Muscle spasm after injury

Arthritis

Question 3

DDx painful clicking (audible) in knee

Answer 3

torn meniscus

Question 4

Ddx giving way (instability) in knee

Answer 4

Cruciate ligament or meniscal tear, patellar dislocation

Question 5

ACL tear mechanism, history and treatment

Answer 5

Sudden deceleration Hyperextension and internal rotation of tibia on femur (i.e. “plant and turn”)

Audible “pop” Immediate swelling Knee “giving way” Inability to continue activity

Stable knee wth minimal functional impairment: immobilization 2-4 wk with early ROM and strengthening High demand lifestyle: ligament reconstruction

Question 6

PCL tear mechanism, history and treatment

Answer 6

Sudden posterior displacement of tibia when knee is flexed or hyperextended (e.g. dashboard MVC injury)

Audible “pop” Immediate swelling Pain with push off Cannot descend stairs

Unstable knee or young person/hgih-demand lifestyle: ligament reconstruction

Question 7

What is O’Donoghue’s Unhappy Triad

Answer 7

ACL rupture

MCL rupture

Meniscal damage (medial and/or lateral)

Question 8

How to determine if there is a partial or complete collateral ligament tear on clinical exam

Answer 8

■ laxity with endpoint suggests partial tear

■ laxity with no endpoint suggests a complete tear

Partial ligamentous tears are much more painful than complete ligamentous tears

Question 9

Collateral ligament tears treatment

Answer 9

• non-operative
■ partial tear: immobilization x 2-4 wk with early ROM and strengthening
■ complete tear: immobilization at 30° flexion

• operative
■ indication: multiple ligamentous injuries
■ surgical repair of ligaments

Question 10

Meniscal tears mechanism

Answer 10

• twisting force on knee when it is partially flexed (e.g. stepping down and turning) • requires moderate trauma in young person, but only mild trauma in elderly due to degeneration

Question 11

Meniscal tears clinical features

Answer 11

• immediate pain, difficulty weight-bearing, instability, and clicking • increased pain with squatting and/or twisting • effusion (hemarthrosis) with insidious onset (24-48 h after injury) • joint line tenderness medially or laterally • locking of knee (if portion of meniscus mechanically obstructing extension)

Question 12

Meniscal tears treatment

Answer 12

• non-operative
■ indication: not locked
■ ROM and strengthening (NSAIDs)

• operative
■ indication: locked or failed non-operative treatment
■ arthroscopic repair/partial meniscectomy

Meniscal repair is done if tear is peripheral with good vascular supply, is a longitudinal tear and 1-4 cm in length Partial meniscectomy is done with tears not amenable to repair (complex, degenerative, adial)

Question 13

Tissue sources for ACL reconstruction

Answer 13

• Hamstring
• Middle 1/3 patellar tendon (bone-patellar bone)
• Allograft (e.g. cadaver)

Question 14

Quadriceps/Patellar Tendon Rupture mechanism and common populations

Answer 14

• sudden forceful contraction of quadriceps during an attempt to stop

• more common in obese patients and those with pre-existing degenerative changes in tendon
■ DM, SLE, RA, steroid use, renal failure on dialysis

Question 15

Quadriceps/Patellar Tendon Rupture clinical features

Answer 15

• inability to extend knee or weight-bear
• possible audible “pop”
• patella in lower or higher position with palpable gap above or below patella, respectively

Patella alta = high riding patella 
Patella baja (infera) = low riding patella

• may have an effusion

Question 16

Quadriceps/Patellar Tendon Rupture investigations

Answer 16

• ask patient to straight leg raise (unable with complete rupture)
• knee X-ray to rule out patellar fracture, MRI to distinguish between complete and partial tears
• lateral view: patella alta with patella tendon rupture, patella baja (infera) with quadriceps tendon rupture

Question 17

Quadriceps/Patellar Tendon Rupture treatment

Answer 17

• non-operative
■ indication: incomplete tears with preserved extension of knee
■ immobilization in brace

• operative
■ indication: complete ruptures with loss of extensor mechanism

• early surgical repair: better outcomes compared with delayed repair (>6 wk post-injury)
• delayed repair complicated by quadriceps contracture, patella migration, and adhesions

Question 18

Dislocated knee mechanism

Answer 18

• high energy trauma

* by definition, caused by tears of multiple ligaments

Question 19

Dislocated knee clinical features

Answer 19

• classified by relation of tibia with respect to femur
■ anterior, posterior, lateral, medial, rotary

• knee instability
• effusion
• pain
• ischemic limb
• Schenck classification

Question 20

Dislocated knee investigations

Answer 20

• X-ray: AP, lateral, skyline
• associated radiographic findings include tibial plateau fracture dislocations, proximal fibular fractures, and avulsion of fibular head
• ABI (abnormal if <0.9)
• arteriogram or CT angiogram if abnormal vascular exam (such as abnormal pedal pulses)

Question 21

Dislocated knee treatment

Answer 21

• urgent closed reduction
■ complicated by interposed soft tissue

• assessment of peroneal nerve, tibial artery, and ligamentous injuries
• emergent operative repair if vascular injury, open fracture or dislocation, non-reducible dislocation, compartment syndrome
• knee immobilization x 6-8 wk

Question 22

Dislocated knee specific complications

Answer 22

• high incidence of associated injuries
• popliteal artery tear
• peroneal nerve injury
• capsular tear
• chronic instability, stiffness, post-traumatic arthritis

Question 23

Schenck classification

Answer 23

Type 1: single ligament injury (ACL or PCL)

Type 2: Injury to ACL and PCL

Type 3: Injury to ACL, PCL and either MCL or LCL

Type 4: Injury to ACL PCL, MCL, LCL

Type 5: Multiligamentous injury with periarticular fracture