PA Axial Intercondylar Fossa Holmblad is a radiography positioning projection of the Lower Extremity. Kneeling on the table, affected knee over the IR, leaning forward, knee flexed 60-70 degrees, CR perpendicular to lower leg. SID 40". The centering point is located midpopliteal crease with patient kneeling and knee flexed 60-70 degrees. The central ray is perpendicular to the lower leg (no tube angle; the flexed-knee position provides the axial projection). Image-quality criteria include intercondylar eminence clearly visualized in axial projection, intercondylar fossa in profile and open, not superimposed by the patella. A sample technique is 70 kVp with DR 2.5 or CR 5 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Intercondylar eminence of tibia.
- Intercondylar fossa and notch.
- Posteroinferior articular surfaces of the femoral condyles.
- Tibial plateau in axial projection.
- Medial and lateral intercondylar tubercles.
- Fibular head in relation to tibia.
Patient preparation
- Verify patient identity using two identifiers.
- Remove shoes and any radiopaque items from the leg.
- Position patient kneeling on the table on all fours, affected knee over the IR.
- Keep the weight mainly on the unaffected knee; pad under the affected ankle and leg.
- Lean forward slowly 20-30 degrees and hold (knee flexed 60-70 degrees).
- Ensure the leg is not rotated.
Position & centering point
Midpopliteal crease with patient kneeling and knee flexed 60-70 degrees.
Central ray
Perpendicular to the lower leg (no tube angle; the flexed-knee position provides the axial projection).
Exposure / technique
- kVp
- 70
- mAs
- DR 2.5 / CR 5
- SID
- 40" (102 cm)
- Notes
- Leaning forward 20-30 degrees gives 60-70 degrees of knee flexion. Bontrager prints a grid and digital 75 +/- 5 kV; the sample is Merrill's nongrid tabletop row. Sample technique: DR 2.5 / CR 5 mAs at 70 kVp, 40 in SID, for a 14 cm part. Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Intercondylar eminence clearly visualized in axial projection.
- Intercondylar fossa in profile and open, not superimposed by the patella.
- No rotation: posterior femoral condyles symmetric, about half the fibular head behind the tibia.
- Tibial plateau included showing intercondylar area.
- Medial and lateral intercondylar tubercles differentiated.
- Collimation: four sides to the knee joint area (Bontrager); 1 inch beyond the sides (Merrill's).
Common errors
- 1 Leaning forward less or more than 20-30 degrees leaves the knee outside 60-70 degrees of flexion.
- 2 CR not perpendicular to the lower leg.
- 3 Rotation: posterior femoral condyles not symmetric.
Clinical indications
- Bony or cartilaginous pathology, osteochondral defects, or joint space narrowing.
- Osteochondritis dissecans of the intercondylar fossa.