Courtesy: Dr S Macdonald, Ashok Shyam TV, Ortho

Don’t Forget Pre-Operative Evaluation

Before analyzing a painful postoperative knee, always revisit:

• Was TKA truly indicated?

• Was there clear bone-on-bone osteoarthritis?

• Could pain have originated elsewhere (e.g., hip)?

Key Clinical Lesson

• Mild radiographic knee arthritis + severe hip arthritis ? knee replacement will not solve the pain.

• Always evaluate:

  • Ipsilateral hip

  • Lumbar spine

  • Referred pain patterns

Inappropriate indication leads to persistent postoperative pain.

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Postoperative Radiographic Assessment: Three Pillars

1. Limb Alignment

2. Balancing

3. Component Alignment & Orientation

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1?? Limb Alignment

Goal

• Mechanical axis:

  • Center of hip ? center of knee ? center of ankle.

Does It Have to Be Perfect?

• Traditional target: ±3° from neutral.

• Long-term data (15-year follow-up studies):

  • No significant difference in function or survivorship between:

    • Knees within 3°

    • Knees outside 3°

Takeaway:

• Aim for neutral.

• Minor deviations may not compromise long-term results.

• Avoid gross malalignment.

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2?? Balancing

Even on early postoperative films, you can assess balance.

What to Look For

• Symmetry between femoral component and polyethylene insert.

• Medial and lateral compartment congruence.

Warning Signs

• Lift-off on one side (especially medial side in former varus knees).

• Asymmetric joint space.

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Joint Line Elevation: Is It Always Bad?

Traditional teaching:

• Elevation = poor function.

Evidence suggests:

• Minor elevation (2–4 mm) does NOT necessarily:

  • Affect function.

  • Reduce survivorship.

  • Alter clinical outcomes.

Key principle:

• Proper flexion–extension gap balance is more important than millimeter-perfect joint line restoration.

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3?? Component Positioning

Malposition can cause:

• Pain

• Stiffness

• Instability

• Increased wear

• Early failure

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? Femoral Component

Sagittal Plane

Target:

• Parallel to femoral shaft.

• Flush with anterior cortex.

Common Errors

Small notches may not be clinically significant.

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Coronal Plane

• 5–7° valgus to anatomical axis.

• Slightly central to lateral placement preferred.

Errors:

• Excess valgus ? wear, pain.

• Medial shift ? patellar instability.

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Rotational Alignment (Most Critical)

Target:

• ~3° external rotation relative to posterior condylar axis.

Pitfall:

• Valgus knees with hypoplastic lateral condyle.

  • Posterior referencing jigs may create internal rotation.

  • Leads to:

    • Patellar maltracking

    • Anterior knee pain

    • Stiffness

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? Tibial Component

Coronal Alignment

• 90° to long axis of tibia.

Malalignment ? excessive polyethylene wear.

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Tibial Slope

Debated topic:

• CR knees: 3° posterior slope common.

• PS knees: some prefer 0°, others still use slope.

Consequences:

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Tibial Rotation

Target:

• Medial one-third of tibial tubercle.

Malrotation leads to:

• Patellar maltracking.

• Patellar instability.

• Anterior knee pain.

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? Patellar Component

Target:

• Central or slightly medial placement.

Common mistake:

• Excess lateral placement ? instability.

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Radiographic Clues to Common Clinical Problems

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Stiff Knee

Look for:

• Oversized components.

• Overstuffed flexion gap.

• Too little tibial slope (especially CR).

• Tight flexion space.

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Instability

Look for:

• Undersized femoral component.

• Loose flexion gap.

• Excess tibial slope.

• Asymmetric polyethylene thickness.

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Persistent Pain

Look for:

• Overhanging components.

• Focal implant prominence.

• Malrotation.

• Joint line mismatch.

• Patellofemoral overstuffing.

Always correlate imaging with clinical exam.

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Final Clinical Pearls

• Not every painful TKA is a technical failure.

• Not every malalignment leads to failure.

• Indication matters as much as execution.

• Evaluate hip and spine in every painful knee.

• Minor radiographic imperfections may be clinically irrelevant.

• Major malrotation errors are rarely forgiving.