How should a total knee arthroplasty be performed in a patient over 60 years old with end‑stage osteoarthritis and a valgus deformity greater than 10° (lateral mechanical axis), intact neurovascular status and no major medical contraindications?

Total Knee Arthroplasty in Valgus Knee: Surgical Technique

For valgus deformity >10°, use a lateral parapatellar approach rather than the standard medial approach, as it provides superior deformity correction, shorter operative times, and better functional outcomes. 1, 2

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Preoperative Planning

Obtain standing full-length hip-to-ankle radiographs to accurately assess the mechanical axis and degree of valgus deformity. 3, 4 Standard AP knee radiographs alone are insufficient for surgical planning in valgus knees. 3

• Obtain standing AP and lateral knee radiographs with 10° internal rotation for detailed joint assessment and accurate valgus/varus alignment evaluation 3, 4
• Add tangential axial views of the patellofemoral joint to assess patellar tilt and subluxation, which are commonly present in valgus knees 4
• Consider CT scanning to determine optimal axial rotation of the femoral component 4
• Identify anatomical variations including lateral cartilage erosion, lateral condylar hypoplasia, contracted lateral structures (LCL, posterolateral capsule, popliteus, IT band, lateral gastrocnemius), and elongated medial structures 5

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Surgical Approach Selection

The lateral parapatellar approach is superior to the medial approach for valgus deformities >15°. 1, 6, 2 This differs fundamentally from the standard medial approach used in varus knees.

Lateral Approach Advantages:

• Corrects deformity more effectively (10.8° correction vs 7.3° with medial approach) 1
• Reduces operative time significantly (87 minutes vs 137 minutes with medial approach) 1
• Achieves higher postoperative KSS Knee scores (85.31 vs 77.42 with medial approach) 2
• Requires fewer constrained implants (9% vs 16% with medial approach) 1
• Provides direct access to contracted lateral structures for release 6, 7
• Improves patellar tracking by correcting patellar tilt (from -2.3° to 0.3°) 1

Lateral Approach Technique:

Make a lateral parapatellar incision 2-4 cm from the patellar edge. 7

• Perform "apple pie" or "Z-plasty" of the iliotibial band to allow adequate exposure and reduce tension on the common peroneal nerve 7
• Extend the arthrotomy through the lateral retinaculum and capsule 6, 7
• Consider tibial tubercle osteotomy (TTO) for severe deformities >20° to facilitate exposure and reduce residual valgus (9% residual valgus with TTO vs 32% without) 6

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Bone Cuts in Valgus Knee (Different from Varus)

Use 5° valgus angle for distal femoral cuts (compared to the standard 5-7° valgus used in neutral/varus knees). 7 This accounts for the altered anatomy in valgus deformity.

• Reference femoral rotation using both Whiteside's line and the transepicondylar axis to ensure proper rotational alignment 7
• Adjust tibial cuts to account for lateral plateau wear and potential metaphyseal remodeling 5
• Plan for potential lateral condylar hypoplasia which may require augmentation or modified component sizing 5

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Lateral Soft Tissue Release Sequence

Release lateral structures sequentially through the lateral approach to achieve balanced flexion and extension gaps. 5, 6, 7 This is the opposite of medial releases performed in varus knees.

Sequential Release Order:

1. Release iliotibial band at Gerdy's tubercle 7
2. Release lateral collateral ligament from femoral origin 7
3. Release posterolateral capsule 7
4. Release popliteus tendon if needed 5
5. Release lateral head of gastrocnemius if persistent tightness 5

Perform releases with the knee flexed during capsule closure to maintain the expanded lateral soft tissue sleeve. 7

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Implant Selection

Use posterior-stabilized implants for most valgus knees >15°. 7 Constrained implants are needed less frequently with the lateral approach (9%) compared to medial approach (16%). 1

• Reserve constrained condylar implants for severe instability after lateral release or MCL incompetence 5, 1
• Resurface the patella routinely in valgus knees to address patellar maltracking 7

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Closure Technique (Critical Difference from Varus Knees)

Close the capsule with the knee flexed to maintain the expanded lateral soft tissue sleeve created by Z-plasty. 7

• Suture the expanded deep lateral soft tissue sleeve (coronal Z-plasty) to the medial retinacular sleeve 7
• Avoid overtightening the lateral closure which can recreate lateral tightness 6

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Postoperative Management

Obtain standing AP and lateral radiographs to assess alignment correction. 4

• Initiate early mobilization to reduce hospital length of stay 4
• Prescribe supervised exercise program for the first 2 months to improve physical function 4
• Schedule radiographic follow-up every 1-2 years long-term 4

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Common Pitfalls to Avoid

• Do not use the standard medial approach for valgus deformities >15° as it results in inferior correction, longer operative times, and higher complication rates (14% vs 9%) 2
• Do not perform bone cuts without full-length standing radiographs as standard knee films cannot accurately measure mechanical axis 3
• Do not close the lateral capsule with the knee extended as this prevents adequate soft tissue balancing 7
• Do not underestimate lateral condylar hypoplasia which may require augments or constrained implants 5