Chapter 48- Knee

Question 1

Fill in the following table for compartments of the lower leg

Answer 1

Question 2

List contents of popliteal fossa

Answer 2

Popliteal Artery
Popliteal Vein
Tibial Nerve
Peroneal Nerve

Question 3

Describe the sensory and motor function of nerves of the lower extremity. For each nerve, include the corresponding compartment

Answer 3

1. Peroneal nerve:
   Compartment: anterior
   Sensory: first toe webspace
   Motor: great toe extension
2. superficial peroneal:
   Compartment: lateral
   Sensory: dorsum of foot
   Motor: foot pronation/ eversion
3. Sural nerve:
   Compartment: superficial posterior compartment
   Sensory: lateral foot
   Motor: plantar flexion
4. Tibial nerve:
   Compartment: deep posterior
   Sensory: plantar aspect of foot
   Motor: foot flexion, long toe flexion

Question 4

Describe the motor and sensory testing for the following nerve roots (per ASIA) L2-S1:

Answer 4

Question 5

What compartment is most likely to be affected by compartment syndrome?

At what pressure are you concerned for compartment pressure?

Answer 5

• Anterior compartment
  -At what pressure are you concerned for compartment pressure?
  > 30 mmhg

Question 6

How do you differentiate a peroneal vs sciatic nerve injury?

Answer 6

Peroneal nerve»_space; foot drop (unable to dorsi flex foot or evert ankle)

Sciatic nerve»_space; Hamstrings (unable to flex knee) unable to dorsi/ plantar flex + every or invert

Question 7

What fracture patterns are you most concerned about peroneal nerve injury?

Answer 7

Fibular fractures

Peroneal nerve wraps around fibula

Question 8

Describe the sensory and motor testing for the peroneal nerve

Answer 8

Motor:
DPN» foot dorsiflexion + great toe extension
SPN» ankle eversion.

Sensory:
- top of foot and lateral lower leg

Question 9

Describe the Ottawa Knee Rules (5)

Answer 9

Clinical decision-making tool 9scoring system) to help decide if a patient needs XR for suspected knee # after trauma

Should be applied to all patients aged 2 and older with knee pain/tenderness in the setting of trauma.

Useful in ruling out fracture (high sensitivity) when negative, but poor for ruling in fractures (many false positives).

Sensitivity 98-100% | Specificity 19-50%

Question 10

Describe the kennedy classification for knee dislocations

Answer 10

Based on direction of displacement

Question 11

Describe the MOI for anterior knee dislocations. What are the most common associated injuries?

Answer 11

Hyperextension mechanism
***most common knee dislocation

PCL tear
Arterial injury
Highest rate of peroneal nerve injury

Question 12

Describe the MOI for posterior knee dislocations. What are the most common associated injuries?

Answer 12

Due to axial load to the flexed knee (dashboard injury)

Highest rate ofvascular injury(complete tear of popliteal artery)

Question 13

Describe the MOI for lateral knee dislocations. What are the most common associated injuries?

Answer 13

Varus or valgus force
Usually involves tears of both ACL/PCL

Question 14

A 50 year old male presents after a fall while running. He felt his L knee give out. On exam his L knee is ++ tender, without obvious deformity. You suspect a spontaneously reduced posterior knee dislocation

What structure would you be most concerned about being injured?

Answer 14

Popliteal artery injury
**Get ABIs

Question 15

List hard and 3 soft signs of lower extremity vascular injury

Answer 15

Hard:
1. lack of distal pulses
2. Palpable thrill
3. Pulsatile hemorrhage
4. Expanding hematoma
5. Classic Ps
- pain
-pallor
-paresthesia
-poikliothermia
-paralysis

Soft:
1. Decreased pulse relative to unaffected side
2. Significant hemorrhage at time of injury
3. Non expanding hematoma
4. Peripheral nerve deficit

Question 16

List 5 components for physical examinatin of the knee

Answer 16

Question 17

List 3 special tests for assessing ACL injuries

Answer 17

1. Anterior drawer
2. Lachman
3. Pivot shift test

Question 18

List 2 special tests for assessing PCL injury

Answer 18

1. Posterior drawer
2. Posterior sag sign

Question 19

List 2 special tests for assessing meniscus injuries

Answer 19

1. Mcmurray
2. Apley

Question 20

List 8 DDx for knee injuries

Answer 20

1. Knee dislocation
2. Distal femur #
3. Tibial plateau #
4. tibial spine #
5. osteochondritis
6. Osteoarthrosis
7. extensor mechanism injury (quads or patellar tendon)
8. Patellar fracture
9. patellar dislocation
10. Cruciate ligament injury
11. Collateral ligament injury
12. Meniscus injury
13. Overuse syndromes

Question 21

List 3 traumatic and 3 atraumatic causes of unilateral knee effusion

Answer 21

Trauma:
- distal femur fracture
-ACL/PCL injury
- dislocation
- tibial plateau or spine fracture

Atraumatic:
- OA
-insufficiency fracture
- septic arthritis
- inflammatory arthritis
- reactive arthritis
- hemarthrosis/lipo-hemarthrosis from occult fracture
- avascular necrosis
- ruptured bakers cyst
- possible malignancy

Question 22

List 6 DDX for Anterior Knee Pain in adults and 2 dx for peds.

Answer 22

1. Patellofemoral pain
   - common cause of anterior knee pain in children/adults and not usually associated w/ bony tenderness
2. Osteochondritis Dissecans
   - gradual onset pain over anterior femoral condyle
3. Busitis
4. Tibial plateau #
5. Extensor mechanism injury
6. Tendinitis

PEDS:
1. Osgood Schlatter disease
- Tenderness over tibial tubercle in peds

2. Salter-Harris fractures

Question 23

List 6 DDx for medial knee pain

Answer 23

1. Meniscal Injuries
   - acute onset joint line pain after twisting mechanism
2. Loose bodies
3. Osteochondritic lesions
4. Tibial fractures
5. Medial tibial stress fractures
6. Proximal medial tibial stress syndrome
7. Per anserine bursitis/tendinopathy
8. MCL/LCL strain
9. IT band dysfunction
10. Popliteal tendinitis
11. Proximal fibular stress fracture

Question 24

List 4 Ddx for posterior knee pain

Answer 24

• Baker’s cysts
• DVT
• Hamstring injury
• Popliteal artery pseudoaneurysm

Question 25

List 4 XR views that should be obtained for suspected knee pathology and their corresponding injuries

Answer 25

1. Tunnel views: used to detected tibial spine fractures and loose bodies within the notch 2. Oblique views: helpful for tibial plateau fractures 3. Sunrise views: essential in evaluating for patellar fractures 4. A/P: evaluate for subluxation, fracture, dislocation, joint space narrowing, foreign bodies

Question 26

43 F presents with L knee pain and effusion from 'twisting' her knee Diagnosis?

Answer 26

lipohemarthrosis. results from an intra-articular fracture with escape of fat and blood from the bone marrow into the joint, and is most frequently seen in the knee, associated with a tibial plateau fracture or distal femoral fracture; rarely a patellar fracture XR Subtle tri-layer appearance due to fat on serum on red cells.

Question 27

List 4 diagnostic tests/imaging should be done for suspected posterior knee dislocation?

Answer 27

1. Gold standard- CT Angiography - high morbidity due to need for femoral artery cannulation. 2. Duplex Ultrasonography - unsure of the role 3. Ankle brachial index  Ratio of systolic brachial BP / systolic ankle BP - If > 0.9 = negative predictive value of 100% in knee dislocation 4. Serial physical exams - 7% miss rate Pedal pulses serially (Sens = 79%, spec = 91%, NPV = 93%)

Question 28

List 2 bedside tests that can be performed in ED for suspected vascular injury of the lower extremity.

Answer 28

US (duplex or doppler) ABI Index (< 0.9 diagnostic)

Question 29

List 5 complications associated with traumatic knee dislocation

Answer 29

1. DVT 2. Compartment syndrome 3. Pseudoaneurysm 4. Arterial thrombosis 5. Limb loss 6. post traumatic arthritis 7. Heterotopic Ossification

Question 30

Outline the management for knee dislocations in the ED

Answer 30

- Reduce at earliest opportunity (traction- counter traction) - Assess neurovascular status before and after - Immobilize in long leg posterior splint w/ knee in 15-20 degrees of flexion after reduction - OR if hard signs or non reducible in ED

Question 31

Lisy 8 ddx for unilateral calf swelling

Answer 31

1. DVT 2. Cellulitis 3. Lymphangitis 4. MSK injury 5. Knee pathology 6. Compartment syndrome 7. Nec fasc 8. Thrombophlebitis 9. Bakers cyst 10. Venous insufficiency

Question 32

List 6 complications associated with distal femur fractures

Answer 32

○ Thrombophlebitis ○ Fat embolus syndrome ○ Delayed union/malunion ○ Angulation deformities ○ Intra-articular or quadriceps adhesions ○ OA

Question 33

Outline the management for distal femur fractures

Answer 33

Femoral nerve block Immobilize with hinged knee brace or splint Ortho consult Definitive mngmt  ORIF +/- IMN

Question 34

26 M with traumatic knee injury Dx?

Answer 34

Segond Fracture Avulsion fracture of lateral tibial plateau Attachment site of LCL Sport injurie flexed knee + internal rotation + varus stress Oval shaped fragment adjacent to lat. Tibia plateau

Question 35

Describe the Schatzker classification for tibial plateaus fractures

Answer 35

Question 36

OUtline the management for tibial plateau #s

Answer 36

Suspect tiial plateau # >> get CT of knee NV of lower extremity - popliteal or ant tibial artery -peroneal nerve ***high risk for compartment syndrome Femoral nerve block NWB Immobilize with hinged knee brace or splint Ortho consult Definitive mngmt = ORIF +/- IMN

Question 37

14 yo M with knee injury while playing football ~ hyperextension and direct trauma. Unable to WB Diagnosis?

Answer 37

Tibial spine fracture (intercondylar eminence) **associated with ACL rupture More common in children MOI- twisting knee movement, hyperflexion, hyperextension Immediate pain and swelling after injury XR: There is an avulsion fracture (red and white arrows) of the intercondylar eminence. There is a also a large suprapatellar hemarthrosis (yellow arrow). Such fractures are associated with injury to the anterior cruciate ligament.

Question 38

Outline the management for Tibial spine fracture (intercondylar eminence)

Answer 38

Immobilize with locked brace NWB Ortho f/u 3-7d

Question 39

18 yo male presenting with AoC knee pain. Diagnosis?

Answer 39

Osteochondritis Dissecans: - Partial or total separation of a segment of articular cartilage and subchondral bone from underlying bone - Cause: acute/chronic trauma, genetics, ischemia - Pain, swelling and episodes where their knee gives way - XR: subcortical lucency - Management: NWB + Ortho follow up in 3-5 day

Question 40

50 yo male presenting with a L knee injury after falling. Direct impact to the anterior knee on concrete Diagnosis? Management?

Answer 40

Patellar tendon rupture XR- large joint effusion. avulsion # at the inferior pole of the patella + superior displacement of the patella Management: Immobilize with G2 brace NWB Otho follow up in 1 week

Question 41

List 6 RF for extensor mechanism injuries

Answer 41

1. chronic systemic illness 2. RA 3. gout 4. SLE 5. hyperparathyroidism 6. immunosuppression 7. steroids 8. fluroquinolones. 9. chronic microtrauma 'jumpers knee'

Question 42

Describe the Insall-Salvati ratio

Answer 42

- Used to diagnose abnormal high/low riding patella - Lateral knee x-ray with knee 30 deg. Flexed Patellar tendon length / patellar length Normal ratio 0.8 - 1.2 (0.74 - 1.5 in other sources) Patella Baja = < 0.8 Patella Alta = >1.2

Question 43

50 yo male presenting with a L knee injury after falling. Direct impact to the anterior knee on concrete on exam, he is unable to extend at the knee and has significant knee effusion and tenderness Diagnosis? Management?

Answer 43

Transverse patellar fracture Immobilize with G2 brace Partial WB Ortho f/u 1 week

Question 44

List 4 types of patellar fractures

Answer 44

Transverse (**most common) Stellate (comminuted) Vertical (marginal) Proximal or distal pole Osteochondral (rare)

Question 45

List 3 common associated injuries with patella #s

Answer 45

1. femoral neck # 2. hip dislocation 3. acetabulum #

Question 46

An ultimate frisbee player presents to your ED after landing a jump – they felt an immediate pop to the R knee, swelling and inability to weight bear. XR of the knee shows a joint effusion with no obvious fracture. What is the most likely injury?  How should this injury be mamnaged?

Answer 46

ACL tear Unlock hinge or G2 brace WBAT F/U ortho 1 week MRI outpatient

Question 47

List 4 MOI for ACL tears

Answer 47

1. Plant/Pivot 2. Stop-and-Jump 3. Landing with knee in valgus stress 4. Direct blow to flexed knee 5. Turf injury - knee flexed + ankle plantar flexed

Question 48

26 yo tennis player, presenting with acute onset anterior knee pain and swelling after playing a tennis match. Patient was able to WB but has had progressive pain and swelling, and now has a catching or clicking sensation. On exam there is a joint effusion with joint line tenderness and clicking with passive flexion/extension What is the most likely diagnosis? List 2 special tests Management?

Answer 48

Meniscus tear (medial most common) Special tests: - mcmurray -appley - Unlocked hinged knee brace - Crutches, WBAT - Ortho follow up If knee is locked: - Attempt to unlock knee □ Pain control: IV analgesics, conscious sedation, intraarticular lidocaine □ Repeatedly perform McMurray maneuver

Question 49

List 6 overuse syndromes

Answer 49

1. Patello-femoral pain syndrome 2. Iliotibial band syndrome 3. Peripatellar Tendinitis 4. Plica syndrome (redundant folds of synovium) 5. Popliteus tendinitis 6. Bursitis

Question 50

List 3 types of bursitis. How are they differentiated from joint traumatic joint effusions?

Answer 50

1. Prepatellar Bursitis- (house maids knee) 2. Septic bursitis 3. Anserine bursitis Clinical diagnosis but requires knee arthrocentesis to rule out septic bursitis

Question 51

44 yo female, coming in with 1 month of progressive L knee swelling and pain. Pain is exacerbated when kneeling on hard surfaces. She cleans for a living and it preventing her from being able to her job. She has no infectious symptoms or history of trauma. On exam, her left knee is swollen, not warm or red. Limited active ROM but preserved passive ROM What is the most likely diagnosis? List 4 RF for this diagnosis List 3 DDx Management?

Answer 51

1. Prepatellar Bursitis MOI: repetitive kneeling on firm surface (house maids knee) Swelling of superficial bursa (overlying lower pole of patella) 2. RF - Repeated stress - Infection - Local trauma - Crystal deposition - Systemic inflammatory arthritis 3. DDx - Septic Bursitis - Anserine Bursitis - OA - Patellar tendinopathy - inflammatory arthritis -RA -Gout 4. Management Clinical diagnosis (XR to r/o other pathology) US + joint aspiration **common site of septic bursitis Therapeutic arthrocentesis + NSAIDs + Ice+ Rest +/- Steroid injection

Question 52

44 male with a history HIV (compliant with treatment) presenting with 2 weeks of progressive L knee pain and swelling. Denies a history of trauma. VS @ triage: T: 38.0, HR: 110, BP: 120/59 SPO2 On exam his L knee is swollen, warm, tender and has reduced ROM. XR knee shows no obvious fracture or abnormality What is the most likely diagnosis? List 4 RF for this diagnosis List 3 DDx Management?

Answer 52

1. Septic bursitis vs Septic arthritis 2. RF -HIV -Immunosuppression -DM -CKD -IVDU 3. DDx -Prepatellar Bursitis - Septic Bursitis - Anserine Bursitis - OA - Patellar tendinopathy - inflammatory arthritis -RA -Gout 4. arthrocentesis, send for - cell count - protein + glucose - gram staining/clx - crystal analysis - Additional>>gonorrhea + lyme CT knee ABX (gram +/ MRSA/MSSA) Ortho for I+D washout

Question 53

34 F presenting with medial knee pain and swelling. Pain exacerbated with exercise, she is a long distance runner and has not been able to complete her runs for > 1week due to pain. Denies a history of infectious symptoms or trauma. She is otherwise healthy. on exam: VS WNL ++ local tenderness over the medial tibia/knee knee swollen, not warm, no erythema normal ROM XR knee shows no obvious fracture or abnormality What is the most likely diagnosis? List 3 RF for this diagnosis List 3 DDx Management?

Answer 53

1. Anserine Bursitis 2. RF - Obese women - OA - Overuse (runners) 3.Ddx - Prepatellar Bursitis - Septic Bursitis - Anserine Bursitis - OA - Patellar tendinopathy - inflammatory arthritis -RA -Gout 4. Management: Clinical diagnosis (XR to r/o other pathology) US + joint aspiration **common site of septic bursitis Therapeutic arthrocentesis + NSAIDs + Ice+ Rest Steroid injection

Question 54

Name 5 causes of monoarticular arthritis that may present in the knee joint?

Answer 54

1. OA 2. Septic 3. Gout 4. Inflammatory 5. Trauma (fracture/ hemarthrosis) 6. Overuse

Question 55

In ALL age groups – what is 1 common organism that may be the culprit of septic arthritis ?

Answer 55

S. aureus

Question 56

List 3 indications and 3 contraindications for knee arthrocentesis

Answer 56

Indications: (1) Diagnostic (2) Therapeutic (3) Injection Contraindications: 1. Coagulopathy (INR > 2.4, PLT < 50) 2. Joint prosthesis 3. Overlying cellulitis 4. Bleeding diathesis 5. Fracture 6. Uncooperative patient

Question 57

Following knee arthrocentesis, what tests should synovial fluid be sent for?

Answer 57

Cell count Glucose + Protein Gram stain + culture Crystal analysis Clinical considerations: Gonorrhea Lyme

Question 58

38 F presents with a posterior knee mass. She first noticed it two months ago. It was much smaller then and not painful. Since then, the mass has increased in size and is causing her discomfort. She has no history of trauma, infectious or b symptoms. physical exam reveals palpable posteromedial fullness. XR knee shows no obvious fracture or abnormality What is the most likely diagnosis? List 3 associated complications for this diagnosis List 3 DDx Management?

Answer 58

1. Bakers (Popliteal) cyst -herniation of the synovial through the posterior capsule of the knee -Can rupture into calf and mimic DVT 2. Acute Complications: - Thrombophlebitis - Leg Ischemia - Nerve entrapment - Compartment syndrome 3. DDx -cystic mass - lipomas - liposarcoma - popliteal artery aneurysm -DVT -neoplasm 4. Diagnosis/ Management - US for diagnosis - investigate cause of knee effusion (degenerative, inflammatory, reactive) - Steroid injection - Surgery (for intraarticular pathology)

Question 59

List 7 DDx for lower leg injuries

Answer 59

Question 60

Describe the Ogden classification for tibial tubercle fractures in children

Answer 60

Type 1: secondary ossification centre # (near patellar tendon insertion) Type 2: fracture extends between primary and secondary ossification centres Type 3: Fracture extends into the primary ossification centre Type 4: Entire proximal tibial physis fractured Type 5: Sleeve avulsion fracture from the secondary ossification centre A: non -displaced B: displaced

Question 61

Out line the management for tibial tubercle fractures in children

Answer 61

1. Type I or minimally displaced: - Non operative -long leg cast in extension for 6 weeks 2.Type II-IV fractures - ortho in ED for ORIF with arthrotomy +/- arthroscopy, +/- soft tissue repair

Question 62

12 yo boy presents with anterior knee pain and swelling. He was playing basketball and noticed the pain while jumping. Became progressively worse during the game and now he is walking with a limp. No hx of trauma, infectious or b-symptoms. On exam, there is focal tenderness over the tibial tubercle. pain on resisted knee extension. No extensor lag. What is the most likely diagnosis? Describe the XR List 3 DDx Management?

Answer 62

1. Osgood-Schlatter Disease - apophysitis of the tibial tubercle - chronic overuse injury due to repeated microtrauma at the PT insertion @ the tibial tuberosity - boys between ages 10-15 years. 2. Fragmentation and soft tissue swelling over the tibial tuberosity. 3. DDx a. Sinding-Larsen-Johansson syndrome (chronic apophysitis or minor avulsion injury of inferior patella pole) b. Osteochondroma of the proximal tibia c. Tibial tubercle fracture **** d. Jumpers knee 4. Management - Rest, ice, analgesia, bracing - Severe cases may be immobilized for 2-3 wk - Sx not an option until epiphysis closed

Question 63

16 yo male with R lower leg injury after a dirt-biking MVC. Unable to WB with deformity to R lower extremity and severe pain. 1. Diagnosis 2. List 4 associated complications 3. Most common nerves injured 4. Management

Answer 63

1. Oblique fracture of the tibial shaft with a posterior displacement. **most common long bone fractures and the second most common type of open fractures 2. Complications - soft tissue or open injuries - compartment syndrome - infection - ipsilateral fractures, e.g. tibial plateau, tibial plafond, femoral shaft, posterior malleolar - neurovascular injuries -DVT, pseudoaneurysm -Fat embolism (long bone) -Delayed healing -malrotation -CRPS 3. Peroneal + posterior tibial nerve 4. Immobilization ** avoid circumferential cast due to compartment syndrome ***Long leg posterior splint - Analgesia >>Posterior tibial nerve block - ED ortho consult for ORIF - Open # = ABX + TDAP

Question 64

Describe antibiotic treatment options for open fractures. What antibiotics should be added for a. severely contaminated wounds b. Farm related inuries c. Fresh water wounds

Answer 64

1. Cefezolin 2 g po/IV x 10 d 2. Severely contaminated wounds > add gentamycin 3-5 mg/kg daily 3. Farm related injuries >> Add Pen G 4. Fresh water wounds (pseudomonas) >> ciprofloxacin/ pip-taz/mero