MSK

Alpha Angle normal <55

1. Find slice on axial oblique with fattest femoral neck.

2. Draw circle (not ellipse) on femoral head bone (not cartilage).

3. Can use vertical/horizontal lines to find the absolute middle of the femoral head.

4. At the middle of the femoral head, draw angle between the fem/neck barrel and where the circle intersects the cortex anteriorly.

Femoral Head/Neck Off-set

Normal >7mm

1. Draw a line along the neck cortex

2. Draw a parallel line and shift it up so that it originates from the femoral head.

3. Measure the distance between the lines

4. Ignore the arrow above

Lateral Center Edge Angle

normal <40

1. On coronal, find center of femoral head. (Can do circles and vertical/horizontal lines)

2. Make angle between vertical line and second line through the lateral acetabular roof margin at the bone (not cartilage).

Acetabular Retroversion

Normal when anterior acetabular margin is in upper medial quadrant.

1. Draw horizontal line through both femoral heads (avoids patient being twisted by accident).

2. Draw second vertical line through femoral head.

3. Can measure angle between anterior acetabular margin and vertical line. Should be positive if normal, negative if abnormal.

Measure patellar tendon length and patella articular surface length.

Normal: 1.2 - 2.0

Patella alta > 2

Measure patellar tendon length and pole to pole of patella.

• Patella baja: <0.74

• Normal: 0.74-1.5

• Patella alta: >1.5

1. Start about 2-3cm above the joint line. Look for where the trochlea looks good.

2. Draw a line through the posterior femoral condyle cortex to avoid a rotated knee.

3. Measure the angle of the lateral trochlea to the posterior line.

4. Normal >11 degrees (means lateral trochlea is not shallow)

1. Start about 2-3cm above the joint line. Look for where the trochlea looks good.

2. Measure the medial and lateral trochlea

3. Medial divided by lateral

4. Normal >0.4 (means lateral trochlea is bigger than medial)

1. Start about 2-3cm above the joint line. Look for where the trochlea looks good.

2. Draw a line through the posterior femoral condyle cortex to avoid a rotated knee.

3. Measure the distance from the top of medial/lateral trochlea and trough of trochlea.

4. Do the equation above.

5. Normal > 3mm (means trochlea is deep enough)

1. Trying to measure the left/right distance between the tibial tuberosity and the trough of the trochlea.

2. Draw a line through the posterior femoral condyle cortex to avoid a rotated knee.

3. Draw perpendicular line through the trochlea trough.

4. Can try copying the line and pasting to all images.

5. Scroll down to tibial tuberosity and measure the distance from the pasted line to the tuberosity.

6. Normal <15mm (means the tuberosity isn't too far lateral)