TRAIN CERTIFY MAINTAIN
Acute Care Musculoskeletal (AC MSK)
CURRICULUM
Advanced skills for certification
a. Probe
Linear probe or high frequency probe of choice (10 MHz or more).
b. Knobology
i. Preset. MSK or small parts.
ii. Depth. Start at 5 cm. Adjust as needed.
iii. Gain. Initially set at mid-range. Adjust as needed.
c. Patient positioning
Patient seated with elbow flexed at 90 degrees with forearm gently resting on patient’s lap or on examination table.
d. Probe orientation
Sagittal (indicator towards patient’s head) and transverse plane (indicator towards operator’s left).
e. Probe grip
a. External landmark
Distal humerus.
b. Internal landmark
Olecranon fossa.
c. Relevant anatomy
Distal humerus, Triceps brachii muscle and tendon, Olecranon fossa, Posterior fat pad, Olecranon, Olecranon bursa, Medial and lateral epicondyles in short axis.
d. Area of interest
Olecranon fossa.
e. Adequate view
i. Long axis: olecranon fossa centred, hyperechoic and well-defined cortices of humerus and olecranon.
ii. Short axis: olecranon fossa centred. Hyperechoic and well-defined medial and lateral epicondyle.
a. Image generation
i. Landmark
- Start scan in the midline of posterior humerus in the sagittal plane.
- Slide distally until olecranon fossa visualized.
- End scan with sweep of olecranon fossa.
ii. Optimize image
- Adjust depth to centre image.
- Increase probe frequency to increase image resolution.
iii. Technique
- This is a POSTERIOR scan!
- Start scan in the midline of posterior humerus in the sagittal plane.
- Centre the humerus by sliding side to side.
Sweep side to side until humeral cortex appears well-defined (thin and bright white).
- Slide distally until the V-shape of the olecranon fossa is seen.
- Centre olecranon fossa on screen.
- Sweep and slide lateral to medial to assess for presence of an effusion in the AOI.
- Turn probe 90 degrees in transverse plane with marker towards operator’s left.
- Centre olecranon fossa on screen.
- Sweep cephalad to caudad or rock probe to make medial and lateral epicondyle appear well-defined.
- Sweep and slide through AOI to assess for presence of effusion.
iv. Interrogate AOI
- Sweep and slide through AOI in LAX and SAX.
b. Image interpretation
The following areas should be evaluated and a binary yes/no conclusion made:
i. Elbow effusion? (YES/NO).
a. If unsure where is humeral cortex in LAX, rotate probe in SAX to confirm.
b. Decrease depth to centre and increase probe frequency to increase resolution.
a. Technique
i. Keep probe steady and perpendicular to the skin.
ii. Effusions can be harder to see if elbow not flexed at 90 degrees.
iii. NERD ALERT! If olecranon bursitis is suspected: extend elbow and use a thick layer of gel to float the probe and avoid compression and displacement of bursal fluid.
b. Image interpretation
- Simple synovial fluid: anechoic.
- Complex fluid (hemorrhage or infection): can vary from hypoechoic to hyperechoic with or without debris.
- Synovial hypertrophy: hyperechoic.
- Joint recess compressibility, redistribution of joint recess content with movement and lack of internal flow on color doppler suggest complex fluid rather than synovial hypertrophy.
ii. The hypoechoic trochlear and capitellum hyaline cartilages can be mistaken for fluid. Remember that cartilage hugs and follows the bone contours and there is no posterior fat pad displacement in the AOI because no effusion is present.
iii. If in doubt, compare with unaffected side.
c. Clinical integration
i. X-rays can miss elbow fractures. In the right clinical context in adults, posterior displacement of hyperechoic fat pad on ultrasound indicates an elbow fracture (most commonly radial head). In pediatrics, posterior displacement of hyperechoic fat pad on ultrasound indicates an elbow fracture (most commonly supracondylar).
ii. Look for effusion in trauma and in painful, red, and swollen joints.
a. Use lots of gel to float probe to limit applied pressure to tender areas.
b. Have flexed elbow resting on a pillow or rolled towels to avoid having elbow unsupported and dangling.
c. PROCEDURAL POCUS: US-guided arthrocentesis of the elbow joint:
i. Rotate probe in transverse plane to avoid triceps brachii tendon in the midline.
ii. Bring biggest pocket of fluid closer to predicted needle entry on screen (better when less travel between needle and target).
iii. We suggest an in-line approach with a needle entry lateral to medial (to avoid neurovascular structures on the medial side).
iv. Remember to avoid triceps brachii tendon by choosing a needle trajectory passing underneath it.
v. EXTRA TIP! For your comfort and easy maneuvering (if patient can tolerate the position), have patient prone on stretcher with affected shoulder ABducted 90 degrees AND elbow flexed 90 degrees.
a. For a negative scan:
i. AOI must be centred and bony cortices of surrounding bones must be well-defined in 2 planes.
ii. AOI must be interrogated looking for an effusion and lack of posterior fat pad displacement in 2 planes.
iii. No pathology is found.
b. For a positive scan:
i. AOI must be centred and bony cortices of surrounding bones must be well-defined in 2 planes.
ii. AOI must be interrogated looking for an effusion and lack of posterior fat pad displacement in 2 planes.
iii. An effusion and/or a posterior fat pad displacement is found.
Document as per CPoCUS guidelines for positives and negatives according to clinical indications:
a. Elbow joint effusion + or –
b. Indeterminate
Prerequisites
Appropriate didactic and practical introduction to technique that must include written materials covering all relevant ultrasound physics, anatomy and theory, a minimum of 30 minutes of live or on-line lectures, and at least 5 introductory proctored elbow (olecranon fossa) scans.
The introductory scans do not count towards certification and do not need to be determinate.
Logged scan requirements
- 5 elbow (olecranon fossa) determinate scans supervised directly by a CPoCUS MSK Track Instructor for the entirety of the scan.
- Determinate scans are defined in ‘Determinate scan requirements’.
- A minimum of x scans (to be determined) must be done ‘unassisted’.
- An unassisted scan is one in which the learner generates a determinate image and uses appropriate troubleshooting maneuvers without any assistance (verbal or physical) from the instructor.
- There is no requirement for a minimum number of positive scans.
- All scans must be recorded in a CPoCUS logbook.
Examinations
Pass mark on CPoCUS elbow (olecranon fossa) written, practical, and visual examinations PLUS appropriate prerequisites AND logged scans as above.
Note: Prerequisites and/or logged scan requirements may be waived if a candidate is awarded a CPoCUS Exception to Certification (see website for application details).
a. Probe
Linear probe or high frequency probe of choice (10 MHz or more).
b. Knobology
i. Preset. MSK or small parts.
ii. Depth. Start at 5 cm. Adjust as needed.
iii. Gain. Initially set at mid-range. Adjust as needed.
c. Patient positioning
d. Probe orientation
e. Probe grip
a. External landmark
b. Internal landmark
c. Relevant anatomy
d. Area of interest
e. Adequate view
i. Dorsal plane: hyperechoic and well-defined (thin and bright white) cortex of DR and RCJ.
ii. Radial plane: hyperechoic and well-defined cortex of DR.
a. Image generation
i. Landmark
- Start scan in LAX dorsal plane in the midline on DR.
- End scan when RCJ is visualized.
- Re-position probe on LAX radial plane of DR.
- End-scan when DR has been imaged distal to proximal.
ii. Optimize image
- Adjust depth to centre image.
- Increase probe frequency to increase image resolution.
- Increase gain to better see white bone cortices.
- Decrease gain to visualize effusions.
iii. Technique
- LAX DORSAL. Start scan in LAX dorsal plane on DR.
- Centre the probe midline on dorsal radius by sliding side to side.
- Sweep probe to obtain hyperechoic and well-defined image of DR cortex.
- Slide distally keeping radius cortex well-defined until RCJ is identified.
- Slide probe radial to ulnar keeping RCJ centred to assess the whole joint space looking for effusion.
- LAX RADIAL. Slide probe radially to visualize RCJ in LAX radial plane.
- Slide proximally to image DR shaft.
- Sweep probe or slide side to side to keep radius cortex well-defined and centred.
- Slide distally to visualize RCJ.
iv. Interrogate AOI
- Scan DR shaft in LAX dorsal and LAX radial planes.
- Identify RCJ.
- Slide radial to ulnar to assess the whole joint in LAX dorsal plane.
b. Image interpretation
The following areas should be evaluated and a binary yes/no conclusion made:
i. DR fracture? (YES/NO).
ii. RCJ fracture? (YES/NO).
a. Rotate probe in short axis to confirm DR cortex line.
b. Decrease depth and increase probe frequency as needed.
a. Technique
i. Failure to image in both LAX dorsal and radial planes can miss fractures. Think about X-rays and their standard 2 views of most things: AP and lateral. We are aiming for the same principle here. In addition, you can also confirm fractures in SAX in the same two planes.
ii. Patient might be unable to tolerate positioning for assessment without analgesia. Use copious amounts of gel to minimize pressure on tender areas and float the probe!
iii. Radius width is not as large as expected making it is easy to lose cortex on screen if probe moves only a few millimeters off in the LAX plane. You can use your non-scanning hand to stabilize your scanning hand on patient.
iv. The RCJ extends from the radial to the ulnar side of the wrist: slide medial (radial) to lateral (cubital) to avoid missing small effusions.
b. Image interpretation
i. Ultrasound only gives information about the interrogated bone surfaces. Complete exam with as many planes as you deem necessary to have a good idea of bone integrity.
ii. Pediatric patients can present with different fracture patterns than adults.
- Fractures in children can present with:
- Cortical gap.
- Cortical bulging.
- Cortical deviation.
- Hematoma covering cortex in all views.
- Remember that normal growth plates have:
-A well-defined cortex line compared to jagged edges of fracture sites.
-No hematoma above them.
-Symmetry with unaffected side! - Immobilize and refer as per local practice when suspecting a growth plate fracture or use other imaging modality.
vi. Ultrasound cannot reliably differentiate between a septic and an aseptic effusion. High clinical suspicion and correlation are warranted and arthrocentesis is recommended to help refine diagnosis and treatment if clinician is worried about a septic joint.
vii. NERD ALERT!! LISTER’S TUBERCLE. A tubercle is a normal bony prominence at the end of a bone, a ‘bone bump’ of sorts. Lister’s tubercle is palpable on the dorsal wrist on the DR. Just palpate yours right now! Don’t make the mistake of calling it a fracture. Its smooth cortical line in continuity with the DR and absence of hematoma should help you recognizing it for what it is: normal anatomy. If in doubt, remember that you can always compare with unaffected side! Lister’s tubercle also serves as a pulley for the extensor pollicis longus and is used as an anatomy landmark in wrist arthroscopy and injections.
c. Clinical integration
i. Look for effusion in trauma or in painful, red, and swollen joints.
ii. Septic arthritis is a surgical emergency. Finding an effusion in a patient with a high suspicion of septic joint warrants urgent surgical consultation.
iii. Clinical correlation needed! If high suspicion remains, use other modalities to further assess for DR fracture.
a. The RCJ is best visualized with wrist in slight flexion. Use of a rolled towel or similar is recommended.
b. DR scan can help with assessment of displaced Colles’ fractures reductions:
i. Note gap between distal and proximal ends of fracture on LAX radial view.
ii. Hematoma block can also be performed following first scan before reduction attempt.
iii. Proceed with reduction attempt.
iv. Assess for adequate reduction by rescanning patient in same LAX radial view.
v. If reduction deemed inadequate, proceed to re-attempt reduction without analgesia wearing off or waiting for confirmatory X-rays!
c. PROCEDURAL POCUS: US-guided RCJ arthrocentesis:
i. Patient can be seated or supine with forearm supported on examination table and wrist in slight flexion (resting on a rolled towel or similar.
ii. Operator is facing the patient.
iii. Probe is placed on dorsal aspect of DR in LAX.
iv. In-plane needle visualization is recommended and needle entry is planned distal to proximal.
v. Use of a probe with a smaller footprint like a hockey stick probe is recommended if available.
vi. If space for needling without hitting the bone is too limited with probe in contact with RCJ, tilt probe 30 degrees cephalad creating a gap at the caudal end.
vii. Fill that gap with sterile gel and float the probe making space for needle entry.
viii. Needle should be visualized at all times.
a. For a negative scan:
i. Must image well-defined DR in LAX dorsal and LAX radial planes.
ii. Must image RCJ in LAX dorsal plane.
iii. Entire RCJ must be scrutinized by sliding probe from radial side to ulnar side of wrist.
iv. No fractures or effusions seen.
b. For a positive scan:
i. Must image well-defined DR in LAX dorsal and radial planes.
ii. Must image RCJ in LAX dorsal plane.
iii. Entire RCJ must be scrutinized by sliding probe from radial side to ulnar side of wrist.
iv. A DR fracture is identified and\or
iv. A RCJ effusion is identified.
Document as per CPoCUS guidelines for positives and negatives according to clinical indications:
a. DR fracture + or –
b. RCJ effusion + or –
c. Indeterminate
Prerequisites
Appropriate didactic and practical introduction to technique that must include written materials covering all relevant ultrasound physics, anatomy and theory, a minimum of 30 minutes of live or on-line lectures, and at least 5 introductory proctored DR/RCJ scans.
The introductory scans do not count towards certification and do not need to be determinate.
Logged scan requirements
- 5 wrist DR/RCJ determinate scans supervised directly by a CPoCUS MSK Track Instructor for the entirety of the scan.
- Determinate scans are defined in ‘Determinate scan requirements’.
- A minimum of x scans (to be determined) must be done ‘unassisted’.
- An unassisted scan is one in which the learner generates a determinate image and uses appropriate troubleshooting maneuvers without any assistance (verbal or physical) from the instructor.
- There is no requirement for a minimum number of positive scans.
- All scans must be recorded in a CPoCUS logbook.
Examinations
Pass mark on CPoCUS DR/RCJ written, practical, and visual examinations PLUS appropriate prerequisites AND logged scans as above.
Note: Prerequisites and/or logged scan requirements may be waived if a candidate is awarded a CPoCUS Exception to Certification (see website for application details).
a. Probe
Linear probe or high frequency probe of choice (10 MHz or more).
b. Knobology
i. Preset. Small parts or soft tissue.
ii. Depth. Minimal.
iii. Gain. Default. Adjust as needed.
c. Patient positioning
d. Probe orientation
e. Probe grip
Pencil grip or c-grip.
a. External landmark
b. Internal landmark
c. Relevant anatomy
Metacarpal, metacarpophalangeal joint
(MCPJ) space, proximal phalanx, medial phalanx, flexor tendon (FT), soft tissue.
d. Area of interest
e. Adequate view
a. Image generation
i. Landmark
- Start scan on metacarpal bone.
- Slide distally to proximal phalanx and again to medial phalanx.
- End scan when MCPJ space centred (MCPJ scan) or when FT centred on screen (FTS scan).
ii. Optimize image
- Use water bath to improve your view.
- Use minimal depth.
- Adjust probe frequency to its highest setting.
iii. Technique
- Start scan at metacarpal bone in long axis (probe marker towards patient’s head). Keep the bone cortex well-defined (bright white and thin) by sweeping or sliding side to side.
- Slide distally towards the proximal phalanx.
- Centre the MCPJ space on screen.
- Sweep to assess for effusion. Rotate probe 90 degrees into transverse to confirm impression.
- Re-centre and rotate probe back to sagittal
- Slide distally towards medial phalanx.
- Centre FT on screen.
- Assess for presence or absence of fluid surrounding the tendon by sweeping.
- Rotate probe 90 degrees to obtain transverse view and confirm impression.
- Compare with contralateral side or unaffected digit if unsure.
iv. Interrogate AOI
- Sweep MCPJ space looking for an effusion (MCPJ scan) in both axes.
- Sweep FT looking for fluid surrounding the tendon (FTS scan) in both axes.
b. Image interpretation
The following areas should be evaluated and a binary yes/no conclusion made:
i. Is there an effusion in the MCPJ space? (YES/NO).
ii. Is there fluid surrounding the FT? (YES/NO).
a. Use highest frequency possible.
b. Use water bath to improve visualization and alleviate the need to press on very tender areas.
a. Technique
i. Failure to centre joint can miss an effusion.
b. Image interpretation
i. Small amounts of fluid can be harder to detect. Compare to an unaffected digit.
ii. Cellulitis and cobblestone appearance of soft tissue can be mistaken for fluid around the FT. Remember your soft tissue layers.
c. Clinical integration
i. MCPJ scan:
- Impossible to distinguish on ultrasound between a septic or an aseptic effusion. Clinical correlation is paramount and tapping the joint recommended for final diagnosis if in doubt.
ii. FTS scan:
- FTS can also be non-infectious (ex: RA patient). Clinical correlation needed!
- Infectious FTS is a surgical emergency. Kanavel’s signs and clinical suspicion should guide your assessment. Call your hand surgeon early!
a. USE A WATER BATH to help with visualization.
b. Use gentle dynamic testing to locate FT. Can be used as Kanavel’s fifth sign!
c. Scrutinize area of maximal tenderness.
a. For a negative MCPJ scan:
i. MCPJ centred and swept in both axes and no effusion found.
b. For a positive MCPJ scan:
i. MCPJ centred and swept in both axes and effusion present.
c. For a negative FTS scan:
i. FT centred and swept in both axes and no fluid found around tendon.
d. For a positive FTS scan:
i. FT centred and swept in both axes and fluid around tendon present.
Document as per CPoCUS guidelines for positives and negatives according to clinical indications:
a. MCPJ space effusion + or –
b. FTS + or –
c. Indeterminate
Prerequisites
Appropriate didactic and practical introduction to technique that must include written materials covering all relevant ultrasound physics, anatomy and theory, a minimum of 30 minutes of live or on-line lectures, and at least 5 introductory proctored MCPJ/FTS scans.
The introductory scans do not count towards certification and do not need to be determinate.
Logged scan requirements
- 5 hand MCPJ/FTS determinate scans supervised directly by a CPoCUS MSK Track Instructor for the entirety of the scan.
- Determinate scans are defined in ‘Determinate scan requirements’.
- A minimum of x scans (to be determined) must be done ‘unassisted’.
- An unassisted scan is one in which the learner generates a determinate image and uses appropriate troubleshooting maneuvers without any assistance (verbal or physical) from the instructor.
- There is no requirement for a minimum number of positive scans.
- All scans must be recorded in a CPoCUS logbook.
Examinations
Pass mark on CPoCUS MCPJ/FTS written, practical, and visual examinations PLUS appropriate prerequisites AND logged scans as above.
Note: Prerequisites and/or logged scan requirements may be waived if a candidate is awarded a CPoCUS Exception to Certification (see website for application details).
a. Probe
b. Knobology
i. Preset. MSK, small parts, or soft tissue.
ii. Depth. Curvilinear probe: start at around 15 cm and adjust as needed. Linear probe: maximal depth and adjust as needed.
iii. Gain. Default. Adjust as needed.
c. Patient positioning.
d. Probe orientation
e. Probe grip
Pencil grip.
a. External landmark
b. Internal landmark
c. Relevant anatomy
d. Area of interest
e. Adequate view
a. Image generation
i. Landmark
- Start the scan distal to the inguinal crease.
- End scan when entire AOI assessed.
ii. Optimize image
- Decrease probe frequency for larger patients.
- Decrease depth in thinner patients.
iii. Technique
- Start the scan distal to the inguinal crease.
- Identify proximal femoral shaft in long axis.
- Slide side to side to centre femoral shaft on screen.
- Sweep probe to obtain a well-defined (thin, bright white) femoral cortex image.
- Slide the probe proximally towards the hip until the femur cortex starts to take on a curved appearance.
- Rotate probe clockwise (on right side) or anti-clockwise (on left side) into the long axis of the femoral neck with probe marker aiming at the umbilicus.
- Slide the probe towards the hip joint.
- Assess the hip joint for fluid.
- Scan the contralateral side for comparison.
iv. Interrogate AOI
- Measure the width of the joint capsule:
- From anterior concavity of the femoral neck or anterior synovial recess.
- To the posterior surface of the iliopsoas.
b. Image interpretation
The following areas should be evaluated and a binary yes/no conclusion made:
i. Hip effusion? (YES/NO).
a. Rotate probe in short axis to confirm which of the white lines seen is the femoral cortex.
a. Technique
i. Be sure to be in the long axis of the femoral head (rotate when femoral shaft appears to be curving).
b. Image interpretation
i. Bilateral joint effusions are harder to identify because patients lack an ‘unaffected side’ for comparison purposes.
ii. A small amount of physiological fluid can be mistaken for a pathological effusion. When in doubt, compare to unaffected side.
iii. Effusions can be described as complex or simple. If effusion is not completely anechoic think about a complex effusion or a synovial hypertrophy. Characteristics of a complex effusion include:
- Compressible.
- Redistribution of fluid with pressure or swirling with compression or joint movement.
- Heterogeneity of fluid with or without debris.
- No flow seen on colour Doppler.
iv. Ultrasound cannot reliably distinguish between a septic or an aseptic effusion. Clinical suspicion and correlation are paramount to making the right diagnosis and arthrocentesis is recommended to help refine diagnosis and treatment if clinician is worried about a septic joint.
c. Clinical integration
i. Septic arthritis is a surgical emergency! When clinical presentation is highly suspicious for an infectious effusion, US-guided arthrocentesis is recommended and urgent consultation warranted.
ii. Pediatric patient presents with systemic viral symptoms with sudden inability to bear weight but they are well-appearing? Think transient hip synovitis or hip flu! Clinical suspicion and correlation are paramount as ‘hip flu’ and septic arthritis are treated very differently. When in doubt, US-guided arthrocentesis can help refine diagnosis.
a. The physiologic fluid in the normal hip joint creates a “stripe sign” between the anterior and posterior reflection of the joint capsule.
b. Presence of the stripe sign excludes pathological effusion.
c. US-guided arthrocentesis of the hip:
i. Use a LAX lateral approach with effusion brought ‘closer’ on screen to expected needle entry.
ii. Use of an in-plane technique is recommended.
iii. Entry of needle recommended in a lateral to medial fashion.
iv. US-guidance decreases pain and procedure time and increases success rate.
v. Remember to call your orthopedic surgeon before attempting an arthrocentesis in patients with a prosthetic hip.
d. NERD ALERT! In case of painful hip without an effusion, IA corticosteroids injection can also be done with US-guidance. Use hydro-dissection to locate joint capsule, remember your anatomical landmarks and go for it!
a. For a negative scan:
i. Must image femoral neck, head, acetabulum, and capsule.
b. For a positive scan in ADULTS:
i. Presence of an effusion ≥ 7 mm or
ii. Difference of ≥ 1 mm with the asymptomatic side.
b. For a positive scan in PEDIATRICS:
i. Presence of an effusion ≥ 5 mm or
ii. Difference of ≥ 1.5-2 mm with the asymptomatic side.
Document as per CPoCUS guidelines for positives and negatives according to clinical indications:
a. Hip effusion + or –
b. Indeterminate
Prerequisites
Appropriate didactic and practical introduction to technique that must include written materials covering all relevant ultrasound physics, anatomy and theory, a minimum of 30 minutes of live or on-line lectures, and at least 5 introductory proctored hip joint scans.
The introductory scans do not count towards certification and do not need to be determinate.
Logged scan requirements
- 8 hip joint determinate scans supervised directly by a CPoCUS MSK Track Instructor for the entirety of the scan.
- Determinate scans are defined in ‘Determinate scan requirements’.
- A minimum of 1 scan must be done ‘unassisted’.
- An unassisted scan is one in which the learner generates a determinate image and uses appropriate troubleshooting maneuvers without any assistance (verbal or physical) from the instructor.
- There is no requirement for a minimum number of positive scans.
- All scans must be recorded in a CPoCUS logbook.
Examinations
Pass mark on CPoCUS AC MSK hip joint written, practical, and visual examinations PLUS appropriate prerequisites AND logged scans as above.
Note: Prerequisites and/or logged scan requirements may be waived if a candidate is awarded a CPoCUS Exception to Certification (see website for application details).
a. Probe
b. Knobology
i. Preset. MSK or small parts.
ii. Depth. Start at 5 cm. Adjust as needed.
iii. Gain. Initially set at mid-range. Adjust as needed.
c. Patient positioning.
d. Probe orientation
Probe indicator directed to the patient’s head in long axis (sagittal plane) and towards patient’s right in short axis (transverse).
e. Probe grip
Pencil grip.
a. External landmark
b. Internal landmark
c. Relevant anatomy
i. Quadriceps tendon: Near field, fibrillar pattern, hyperechoic, under the subcutaneous fat.
ii. Suprapatellar fat pad: Proximal to superior pole of patella, under quadriceps tendon.
iii. Anterior cortex of femur.
iv. Pre-femoral fat pad: Superficial to the femur (large hyperechoic space).
v. Suprapatellar recess: Communicates (in most patients) with the knee joint (thin and hypoechoic when empty, generally hypo or anechoic pouch when present).
d. Area of interest
e. Adequate view
a. Image generation
i. Landmark
- Start the scan in the sagittal plane, anteriorly and midline on the distal femur near the superior pole of the patella.
- End scan when joint space swept in 2 planes.
ii. Optimize image
- Adjust depth to centre image.
- Adjust gain and probe frequency as required.
iii. Technique
- LAX SPR. Start scan on the distal femur near superior patellar pole.
- Centre probe midline by sliding side to side.
- Sweep probe until a well-defined (thin, bright white) distal femur cortex image is obtained.
- Slide distally until SPR comes into view.
- You should see well-defined distal femur, patella and the SPR on the same image.
- Slide lateral to medial to scan the whole recess looking for an effusion.
- SAX SPR. Once you’ve found the SPR In LAX, turn probe 90 degrees with probe marker to patient’s right.
- Re-scan SPR by sliding medial to lateral in SAX.
- Find the biggest pocket of fluid and assess for best possible needle entry (for arthrocentesis).
iv. Interrogate AOI
- SPR imaged with distal femur, patella and SPR visualized in same plane.
- Scan SPR in LAX by sliding medial to lateral looking for an effusion.
- Rotate probe in transverse to image SPR in SAX and slide medial to lateral.
b. Image interpretation
The following areas should be evaluated and a binary yes/no conclusion made:
i. Evidence of effusion in the SPR? (YES/NO).
a. Make sure to see the femoral cortex and the superior pole of patella to identify the SPR.
b. Make sure to image the area located between the quadriceps tendon/suprapatellar fat pad anteriorly and the pre-femoral fat pad posteriorly.
c. Interrogate this area by sliding lateral and medial in the LAX and SAX.
d. Modify depth and gain if necessary.
a. Technique
i. Up to 15% of patients do not have direct communication between their SPR and the knee joint. They have some form of embryologic remnant membrane either isolating the SPR partially or completely from the joint. Be aware of that variation and remember that if high clinical suspicion remains, you can scan the joint on its lateral or medial side.
ii. Position the knee in flexion to avoid missing a small effusion.
b. Image interpretation
i. Hypertrophy of synovial membrane can have a similar appearance to a complex effusion.
ii. Effusions can be described as complex or simple. If effusion is not completely anechoic think about a complex effusion or a synovial hypertrophy.
- Characteristics of a complex effusion include:
- Compressible.
- Redistribution of fluid with pressure or swirling with compression or joint movement.
- Heterogeneity of fluid with or without debris.
- No flow seen on colour Doppler.
- Differential for complex effusions is vast and includes gout, hemorrhage, lipo-hemarthrosis (think about a fracture in the vicinity) and infection.
iii. Ultrasound cannot reliably distinguish between a septic or an aseptic effusion. High clinical suspicion and correlation are warranted and arthrocentesis is recommended to help refine diagnosis and treatment if clinician is worried about a septic joint.
c. Clinical integration
i. Look for effusions in patients who sustained trauma or in a painful, swollen, or red joints.
ii. Septic arthritis is a surgical emergency. If infectious cause of effusion is suspected, US-guidance arthrocentesis is recommended and prompt surgical consult warranted.
a. To help identify smaller effusions.
i. Ask the patient to contract their quadriceps while having the knee flexed on a rolled towel (isometric contraction).
ii. Apply pressure on the lateral and medial sides of the knee joint at the same time (pushing fluid proximally into SPR) with the free hand while scanning.
iii. Effusions are generally best seen on the superolateral side of SPR as the synovial pouch (in its continuity with the knee joint) tends to protrude in that zone in most patients. When in doubt compare with unaffected side.
b. US-guided arthrocentesis of the knee:
i. Use a SAX lateral (or medial) approach with effusion brought ‘closer’ on screen to expected needle entry (less traveling before hitting fluid by sliding biggest pouch towards screen entry of needle).
ii. Use of an in-plane technique is recommended.
iii. Entry of needle recommended in the soft tissue area between the iliotibial band and the vastus externalis to avoid puncturing quadriceps tendon.
iv. US-guidance decreases pain and procedure time and increases amount of fluid tapped and success rate.
v. Can also assess for any residual fluid left behind and redirect needle further into fluid pocket under US-guidance as needed.
vi. Remember to call your orthopedic surgeon before attempting an arthrocentesis in patients with a prosthetic knee.
vii. In case of painful knee without an effusion, corticosteroids injection can also be done with US-guidance. Use hydro-dissection to locate SPR and remember your anatomical landmarks to avoid injecting into the quadriceps tendon.
a. For a negative scan:
i. Must image a well-defined distal femur, superior pole of patella and the SPR between the quadriceps tendon/suprapatellar fat pad and the pre-femoral fat pad in LAX.
ii. SPR has been interrogated in its entirety in LAX and SAX.
b. For a positive scan:
i. Must image a well-defined distal femur, superior pole of patella and the SPR between the quadriceps tendon/suprapatellar fat pad and the pre-femoral fat pad in LAX.
ii. SPR has been interrogated in its entirety in LAX and SAX.
iii. Effusion identified.
Document as per CPoCUS guidelines for positives and negatives according to clinical indications:
a. Knee effusion + or –
b. Indeterminate
Pre-requisites
Appropriate didactic and practical introduction to technique that must include written materials covering all relevant ultrasound physics, anatomy and theory, a minimum of 30 minutes of live or on-line lectures, and at least 5 introductory proctored knee SPR scans.
The introductory scans do not count towards certification and do not need to be determinate.
Logged scan requirements
- 6 knee SPR determinate scans supervised directly by a CPoCUS MSK Track Instructor for the entirety of the scan.
- Determinate scans are defined in ‘Determinate scan requirements’.
- A minimum of 1 scan must be done ‘unassisted’.
- An unassisted scan is one in which the learner generates a determinate image and uses appropriate troubleshooting maneuvers without any assistance (verbal or physical) from the instructor.
- There is no requirement for a minimum number of positive scans.
- All scans must be recorded in a CPoCUS logbook.
Examinations
Pass mark on CPoCUS AC MSK knee SPR written, practical, and visual examinations PLUS appropriate pre-requisites AND logged scans as above.
Note: Logged scanning and/or pre-requisites may be waived if a candidate is awarded a CPoCUS Exception to Certification (see website for application details).
a. Probe
b. Knobology
i. Preset. MSK or small parts.
ii. Depth. Start at 5 cm. Adjust as needed.
iii. Gain. Default. Adjust as needed.
c. Patient positioning.
d. Probe orientation
e. Probe grip
Pencil grip.
a. External landmark
b. Internal landmark
c. Relevant anatomy
i. Distal tibia: thin strait white line seen cephalad, dropping far field caudad.
ii. Talus dome: thin white line, convex anteriorly.
iii. Anterior fat pad: hyperechoic structure located in the V or U-shape formed by distal tibia and talus.
iv. Anterior tibialis tendon: large fibrillar structure seen in long axis on the medial aspect of the anterior ankle.
v. Anterior tibialis artery / dorsalis pedis artery: small pulsatile vessel (2 mm) lateral to anterior tibialis tendon under the extensor hallucis longus tendon with deep peroneal nerve found alongside its course.
d. Area of interest
e. Adequate view
i. Imaging the ankle joint: well-defined (thin, bright white) distal tibia and talar dome with the anterior fat pad in LAX and in SAX.
ii. Finding and mapping the course of the anterior tibialis tendon AND artery in SAX.
a. Image generation
i. Landmark
- Start the scan in the sagittal plane midline on the anterior distal tibia near the ankle.
- End scan when AOI interrogated in LAX and SAX.
- Optional ending if arthrocentesis planned: End when anterior tibialis artery’s course identified and mapped in SAX.
ii. Optimize image
- Adjust depth to centre image.
- Increase probe frequency to increase image resolution.
iii. Technique
- Start scan on anterior distal tibia in long axis close to the ankle joint.
- Centre probe midline on the tibia by sliding side to side.
- Sweep to make tibial cortex appear well-defined (thin and bright white).
- Slide distally until ankle joint is reached and both tibial and talar cortices appear well-defined.
- Interrogate AOI by sliding medial to lateral looking for an effusion.
- Turn probe 90 degrees in SAX and repeat interrogation of AOI.
- If planning for arthrocentesis:
- In SAX, look for anterior tibialis artery coursing along anterior tibialis tendon.
- Centre pulsating artery on screen by decreasing depth and by sliding side to side.
- Slide proximal to distal keeping artery centred and map its course by marking patient’s skin every 1 cm.
iv. Interrogate AOI
- Anterior recess of the ankle joint visualized with distal tibia and talar dome cortices well-defined.
- Scan in the LAX and slide medial to lateral to see small effusions.
- Scan in the SAX and slide medial to lateral to see small effusions.
If planning for arthrocentesis: map the course of anterior tibial artery.
b. Image interpretation
The following areas should be evaluated and a binary yes/no conclusion made:
i. Evidence of effusion in the ankle tibiotalar joint? (YES/NO).
a. The ankle joint has the classic V-shape US-appearance of most joints. Make sure to see this sharp ‘drop’ of the distal tibia and the curved talar dome as these represent your AOI!
b. If in doubt about which white line in LAX is the tibial cortex, rotate probe in transverse plane to image distal tibia in SAX.
c. Adjust depth and gain as needed.
a. Technique
i. Small effusions can be missed if tibiotalar joint not interrogated entirely. Slide medial to lateral while keeping ankle joint centred to make sure not to miss any effusion. Confirm in SAX. Scrutinize lateral area under talofibular ligament.
ii. Contact between probe and AOI can be difficult because of its anatomical sharp angles. Put patient’s ankle in slight plantar flexion to facilitate contact.
iii. If this is not enough to get adequate contact between probe and AOI, put copious amounts of gel on the area and float the probe.
b. Image interpretation
i. Hypertrophy of synovial membrane can have a similar appearance to a complex effusion.
ii. Effusions can be described as complex or simple. If effusion is not completely anechoic think about a complex effusion or a synovial hypertrophy.
- Characteristics of a complex effusion include:
- Compressible.
- Redistribution of fluid with pressure or swirling with compression or joint movement.
- Heterogeneity of fluid with or without debris.
- No flow seen on colour Doppler.
- Differential for complex effusions is vast and includes gout, hemorrhage, lipo-hemarthrosis (think about a fracture in the vicinity) and infection.
iii. Ultrasound cannot reliably distinguish between a septic or an aseptic effusion. High clinical suspicion and correlation are warranted and arthrocentesis is recommended to help refine diagnosis and treatment if clinician is worried about a septic joint.
iv. Up to 2 mm of fluid can be found in the normal tibiotalar joint.
v. Talar cartilage can be mistakenly labeled as effusion. Remember that the talus is normally surrounded by a thin anechoic line (1-2 mm) representing cartilage. Cartilage is a thin anechoic line that hugs the bone contours smoothly. Effusions are typically:
- Anechoic.
- Teardrop shape.
- Spreading on the talar dome and possibly towards distal tibia.
- Effusions displace the articular capsule and the fat pad anteriorly.
vi. If doubt remains, comparison with unaffected side should help narrow down the differential.
c. Clinical integration
i. Look for effusions in patients presenting with inflammatory pathologies (ankle joint is second most frequent site for gout), trauma, OA (uncommon) and infection (rare).
ii. Septic arthritis is a surgical emergency. If infectious cause of effusion is suspected, US-guidance arthrocentesis is recommended and prompt surgical consult warranted.
a. To help identify smaller effusions.
i. The anterior recess is the best area to look for a tibiotalar effusion.
ii. Dorsiflexion can help increase the size of the effusion on screen while excessive plantar flexion can shift away the effusion from the anterior recess making it harder to detect.
b. US-guided arthrocentesis of the ankle joint:
i. Anterior tibialis tendon should be seen and avoided (tendons in the anterior part of the ankle, from medial to lateral are anterior tibialis, extensor hallucis longus and extensor digitorum longus).
ii. Anterior tibialis /dorsalis pedis artery’s course should be mapped and avoided. The artery is located lateral to the anterior tibialis.
iii. Mark artery course on patient with a Sharpie pen by centring artery on screen (centre of screen= centre of probe).
iv. We recommend using and in-plane LAX caudal to cephalad approach with a planned needle trajectory course MEDIAL to anterior tibialis tendon.
v. Probe is centred on the joint.
vi. Trick of the trade: if there is not enough space to needle in-plane with linear probe without hitting the talar dome, tilt probe about 30 degrees cephalad to raise the caudal end and fill this gap with sterile gel. Image will remain unchanged and you will be able to advance needle in-plane. You can also slide the probe proximally without tilting.
vii. Shortest excursion of needle before hitting fluid decreases chances to hit bone
viii. If available, the use of a probe with a smaller footprint like a hockey stick probe is recommended.
ix. You can also use an out of plane technique keeping the probe in sagittal plane or rotating it in transverse while centring pocket of fluid on screen and avoiding main tendinous and neurovascular structures.
a. For a negative scan:
i. Must image a well-defined distal tibia and talar dome cortices, joint space (possibly virtual) and fat pad.
ii. Must interrogate AOI by sliding medial to lateral in both LAX and SAX.
b. For a positive scan:
i. Must image well-defined distal tibia and talar dome cortices, joint space (possibly virtual) and fat pad.
ii. Must interrogate AOI by sliding medial to lateral in both LAX and SAX.
iii. Effusion identified.
iv. If sonographer plans to do an arthrocentesis of the tibiotalar joint:
- Must identify anterior tibial artery in SAX and map its course on patient.
Document as per CPoCUS guidelines for positives and negatives according to clinical indications:
a. Ankle joint effusion + or –
b. Indeterminate
Prerequisites
Appropriate didactic and practical introduction to technique that must include written materials covering all relevant ultrasound physics, anatomy and theory, a minimum of 30 minutes of live or on-line lectures, and at least 5 introductory proctored ankle tibiotalar joint scans.
The introductory scans do not count towards certification and do not need to be determinate.
Logged scan requirements
- 6 ankle tibiotalar joint determinate scans supervised directly by a CPoCUS MSK Track Instructor for the entirety of the scan.
- Determinate scans are defined in ‘Determinate scan requirements’.
- A minimum of 1 scan must be done ‘unassisted’.
- An unassisted scan is one in which the learner generates a determinate image and uses appropriate troubleshooting maneuvers without any assistance (verbal or physical) from the instructor.
- There is no requirement for a minimum number of positive scans.
- All scans must be recorded in a CPoCUS logbook.
Examinations
Pass mark on CPoCUS AC MSK ankle tibiotalar joint written, practical, and visual examinations PLUS appropriate prerequisites AND logged scans as above.
Note: Prerequisites and/or logged scan requirements may be waived if a candidate is awarded a CPoCUS Exception to Certification (see website for application details).