knee imaging and LE DDx Flashcards
1
Q
Imaging choices
A
- X-ray: Fx, dislocation, non-traumatic, disorders (OA)
- CT: tibial plateau fx depression, articular defect, fragmentation
- MRI: ligaments, menisci, articular cartilage, osteochondral fx, osteochondritis dissecans
- MSK US: intraosseous & extra osseous assessment of lesion
2
Q
Describe the post traumatic knee pain application of Ottawa rules pathway
A
- X-ray indicated or not indicated
- Indicated = Fx or no Fx; Not indicated = ongoing suspicion or likely soft tissue injury
- Fx = treat; No Fx = ongoing suspicion or likely soft tissue injury
- Ongoing suspicion = CT; Likely soft tissue injury = MRI when available
- CT = normal with high clinical suspicion = bone scan
3
Q
X-ray is indicated if any of these are present for the Ottawa rules
A
- Age ≥55
- Tenderness at head of the fibula
- Isolated tenderness of the patella
- Inability to flex knee to 90º
- Inability to weight bear 4 steps both immediately & in the emergency department
4
Q
Describe the non traumatic hip or knee pain pathway
A
- X-ray = cause of pain found or cause of pain not found
- Pain found = further investigation; Pain not found = further investigation based on suspicion
- Further invest = mild arthritis or mod-severe arthritis
- Mild = conservative management; Mod-severe = referral to orthopedics
- Suspected Fx = go to suspected hip fx pathway or go to traumatic knee pain pathway
- Suspected bone metastases = bone scan generally preferred
- Suspected infection = septic arthritis or osteomyelitis
- Septic arthritis = joint aspiration & antibiotics; Osteomyelitis = go to suspected osteomyelitis pathway
5
Q
Describe the suspected acute osteomyelitis pathway
A
- X-ray = negative/equivocal or positive
- Negative = bone scan/MRI; Positive = treat
- Bone scan = osteomyelitis unlikely or osteomyelitis likely
- Osteomyelitis likely = specificity can be improved with a number of tests
- Number of tests = most commonly used, verbal disease & MRI not already performed, or labeled white cell scan & MRI are not available
- Most commonly used = labeled white cell scan; vertebral disease & MRI not yet performed = MRI; Both unavailable = Gallium scan
6
Q
Describe a routine x-ray evaluation of the knee
A
- 4 projections
- Anteroposterior: patella is obscured bc it’s superimposed over the distal femur
- Lateral: demos patellofemoral joint in profile, good for patella view & joint effusion
- Intercondylar fossa view: demos intercondylar fossa, poster femoral condyles, & intercondylar eminence of tibial plateau
- Tangential (Sunrise/Merchant) patellofemoral view: demos patella & articular relationship of patellofemoral joint at one point in ROM
7
Q
Describe the fabella
A
- An accessary ossicle typically found in the lateral head of the gastrocnemius
- Occurs in ~20% of population
8
Q
Describe the Pittsburgh decision rules for knee trauma; order x-ray if patient has the following characteristics
A
- Blunt trauma or fall MOI
- AND age <12 or >50 AND/OR inability to walk 4 weight bearing steps in the emergency department
9
Q
What are the types of tibial plateau fractures using Schatzker classification system
A
- Type I: Split
- Type II: Split-depression
- Type III: Central depression
- Type IV: Split fracture, medial plateau
- Type V: Bicondylar fracture
- Type VI: Dissociation of metaphases & diaphysis
10
Q
Fractures of the proximal tibia in adults occur most frequently where
A
- At the medial and lateral tibial plateaus when various or valgus forces combined with axial compression cause the hard femoral condyle to impact & depress the softer tibia plateau
11
Q
Non-operative versus operative treatment for tibial plateau fractures
A
- Non-operative: indicated for minimally displaced fx & in elderly with osteoporosis; non-WBing for 4-6 wks, partially WBing until solid bony union is x-rayed evident
- Operative: indicated with significant articular surface depression or displacement, open fx, or ruptured ligaments
12
Q
Types of patella fractures
A
- Vertical
- Transverse, nondisplaced
- Transverse, displaced
- Comminuted (stellate), nondisplaced
- Comminuted, displaced
- Avulsed fragments
13
Q
Advanced imaging of the knee
A
- CT exam occurs from the supra patellar region to the proximal tibiofibular joint, scanning plane is parallel to the tibial plateau
- CT data is viewed as axial slices & reformatted into sagittal and coronal planes
- MRI exam occurs from the quads tendon to the tibial tuberosity;, axial, sagittal, and coronal images are obtained
14
Q
Articular cartilage injuries
A
- Osetochondral fracture
- Osteochondritis Dissecans (OCD)
15
Q
Describe osteochondral dissecans (OCD)
A
- Condition seen in older children to young adults particularly those active in sports
- Symptoms: dull pain, subtle limp, mechanical symptoms (popping, locking), & joint effusion (all exacerbated by WBing)
- Considered a chronic form of osteochondral fx
- Non-weight bearing medial femoral condyle is involved up to 85% of the time
