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
16
Q
Different types of meniscal tears
A
- Vertical tear
- Bucket handle tear
- Peripheral tear
- Horizontal radial tear
- Discoid meniscus
17
Q
Describe Osgood-Schlatter Disease
A
- 11-15 yrs onset
- Growth spurts
- Males > females
- Self limiting
18
Q
Describe a Sinding-Larsen-Johansson Syndrome
A
- Osseous fragmentation at the distal pole of the patella
- Pain at the bottom of the kneecap (patella)
19
Q
Describe degenerative joint disease (DJD)
A
- Most common type of arthritis characterized by degeneration of articular cartilage
- Sx: pain worse with WBing, intermittent joint effusions, loss of function & virus/valgus deformities in later stages
- Imaging: X-ray demos hallmarks of DJD
20
Q
Characteristic radiographic signs of degenerative joint disease at the knee may include
A
- Decreased radiographic joint space
- Sclerosis of subchondral bone
- Osteophyte formation at joint margins
- Subchondral cyst formation
- Varus or valgus joint deformity
21
Q
Describe Kellgren-Lawerence grading scale
A
- Grade 1: Doubtful = minute osteophyte, doubtful significance
- Grade 2: Mild = definite osteophyte, normal joint space
- Grade 3: Moderate = moderate joint space reduction
- Grade 4: Severe = joint space greatly reduced, subchondral sclerosis
22
Q
Describe a fracture of the femur
A
- Traumatic fracture describe by location
- Sx: pain, inability to bear weight, swelling
- MOI: high energy collision (MVA) or falls from heights, may occur from ground level falls in elderly with demineralized bone
- Imaging: x-rays are diagnostic, CT may be needed for fragment localization
23
Q
Describe a fracture of the tibial plateau
A
- Sx: pain, inability to bear weight or flex knee, knee joint effusion
- MOI: valgus/varus force combined with axial loading
- Imaging: x-ray is diagnostic, 3D CT may assist in surgical planning, MRI will define occult fx via bone marrow edema
24
Q
Red flags for peripheral arterial occlusive disease
A
- Age >60 yrs
- Hx of Type II DM
- Hx of ischemic heart disease
- Hx of smoking
- Sedentary lifestyle
- Concurrent intermittent claudication
- Unilaterally cool extremity
- Prolonged capillary refill (>2 secs)
- Decreased pulses in arteries below level of occlusion
- Prolonged vascular filling time
- Ankle brachial index (ABI) <0.90
25
Red flags for DVT (deep view thrombosis)
- Recent surgery, malignancy, pregnancy, trauma, or leg immobilization
- Calf pain, edema, tenderness, warmth
- Calf pain that is intensified with standing or walking & relieved by rest & elevation
- Possible pallor & loss of dorsals pedis pulse (dorsal pedal pulse)
26
Red flags for compartment syndrome
- Hx of blunt trauma, crush injury, or unaccustomed exercise
- Severe persistent leg pain that is intensified with stretch applied to involved muscles
- Swelling, exquisite tenderness & palpable tension/hardness of involved compartment
- Paresthesia, paresis, pallor, pulselessness
27
Red flags for septic arthritis
- Hx of recent infection, surgery, or injection
- Coexisting immunosuppressive disorder
- Constant aching or throbbing pain, joint swelling, tenderness, warmth
- May have elevated body temperature
28
Red flags for cellulitis
- Hx of recent skin ulceration or abrasion, venous insufficiency, congestive heart failure (CHF), or cirrhosis
- Pain, skin swelling, warmth, advancing irregular margin of erythema/reddish streaks
- Fever, chills, malaise, & weakness
29
Evaluation for vascular claudication
- Fixed walking distance
- Standing palliative factor
- Walking provokes Sx
- Painful walking uphill
- Positive bicycle test (painful)
- Absent pulse
- Loss of hair & shiny skin
- Rarely weak
- Occasional back pain
- Cramping distal to proximal pain
- Atrophy is uncommon
30
Evaluation of neurogenic claudication
- Variable walking distance
- Sitting/bending palliative factor
- Walking/standing provokes Sx
- Painless walking uphill
- Negative bicycle test
- Present pulse
- Occasional weak
- Commonly has back pain
- Limited back motion
- Numbness, aching proximal to distal
- Occasionally have atrophy
31
Remote causes of referred knee pain
- Hip AVN or OA
- Lumbar L4, L5, S1 radiculopahty
32
Local causes of referred knee pain
- Dislocation
- Baker's cyst
- Bursitis: infra patellar, Pes Anserine, Prepatellar
- CRPS
- DVT
- Discoid meniscus
- Fracture: intercondylar eminence, osteochondral surface, patella, supracondylar
- Gout
- hemarthrosis
- Metastases: breast, kidney, lung, prostate, thyroid disease
- Hoffa's disease
- IT band friction syndrome
- Meniscus tear
- Muscle straina
- Nerve entrapments
- Popliteal artery occlusion
- PFPS
- OA/RA/Septic arthritis
- Reiter's syndrome
- Ruptures and tears
- Tendonitis
33
Types of knee tumors
- Chrondroblastoma: young male, benign
- Chondrosarcoma: tumor in cartilage, surgery
- Osteochondroma: end of long bone, grows away, single lesion
- Osteosarcoma: most common malignancy, 20s, surgery
- Osteoid osteoma: benign, children, self limiting, resolves on own 2-4yrs
- Parosteal Osteosarcoma: surgery, encircles end of long bone, variant of osteosarcoma
- Ganglion cyst: near insertion of lig., sx not always required
- Saint cell tumor: females > males, 20-40yrs, aggressive, benign, local
- Synovial chondromatosis: benign, synovial lining calcifies
- Synovial sarcoma: chemo plus sx, malignant mesenchymal neoplasm
