TKA – Evaluation Of The Failed Or Painful TKA

Modern Study Review (AI-Generated)

High-Yield Summary

Evaluation of a failed or painful Total Knee Arthroplasty (TKA) is critical to identify underlying causes such as infection, mechanical failure, or instability, which directly impact patient outcomes. A systematic approach combining detailed history, focused physical examination, and targeted imaging guides diagnosis. Early identification of periprosthetic joint infection (PJI) remains paramount, as it alters treatment strategy. Modern management balances non-operative and surgical options tailored to the specific failure mechanism to optimize pain relief and function.

Key Diagnostic Findings

| Physical Exam | – Gait analysis for instability or antalgic pattern.

• Wound inspection for infection signs.
• Extensor mechanism: integrity, patellar tracking, extensor lag, active/passive ROM.
• Ligamentous stability tested at full extension, 30°, and 90° flexion for varus/valgus laxity.
• Limb alignment (varus/valgus).
• Adjacent joints (hip, spine, foot/ankle) to rule out referred pain. |

| Imaging | – Standing AP, lateral, notch, and skyline views.

• Look for component shift, fracture, or radiolucent lines >2 mm indicating loosening.
• Patellar bone stock, thickness of resection, alignment, patella alta/baja. |

| Laboratory & Aspiration | CBC, ESR, CRP for infection screening.

• Joint aspiration with synovial fluid analysis and culture is gold standard to rule out PJI. |

Current Gold Standard Treatment

| Infection (PJI) | – Two-stage revision arthroplasty is gold standard for chronic infection.

• Debridement, antibiotics, and implant retention (DAIR) may be considered in early acute infections. |

Modern Complications & Outcomes

• Persistent pain after TKA may indicate subtle infection, instability, or component malposition.
• Periprosthetic joint infection remains the most serious complication, requiring prompt diagnosis and treatment to prevent morbidity.
• Extensor mechanism failure leads to significant functional impairment and often requires complex reconstruction.
• Revision TKA has higher complication rates than primary TKA, including infection, stiffness, and instability.
• Outcomes depend on accurate diagnosis, appropriate surgical technique, and patient factors such as bone quality and comorbidities.
• Board Exam Focus: Know the diagnostic criteria for PJI (MSIS criteria), indications for DAIR vs. revision, and classification of instability patterns.

Classic Clinical Notes

Evaluation of the Failed or Painful Total Knee Replacement

History

• Original diagnosis
• WWF CART
• Post-op problems, especially infection
• Any sounds of grating

Physical

• Gait
• Wound – what kind; is there signs of infection
• The extensor mechanism is KEY – a common source of failure. Is it intact? What is the patellar tracking like? Is there an extensor lag? What is the ROM actively and passively
• The ligaments – in full extension, 30 and 90 degrees of flexion – is there ligamentous laxity with varus/valgus malalignment
• The alignment – varus/valgus
• Don’t forget to examine the hip, spine, foot/ankle

Xrays – standing AP, lateral, notch, skyline

• Component shift or fracture
• Complete radiolucency of 2 mm around implant is significant for loosening – the x-ray technique can easily obscure this though!
• Evaluate the patella very closely – is there enough bone left? What was the thickness of resection? Is it aligned? Is there patella alta or baja?

Rule out Sepsis!

• CBC, ESR, CRP, and aspiration – do not hesitate to aspirate knees. The hip literature and algorithm is not applicable to knees.

Consider diagnostic marcaine block if confused about source of pain

Consider the Diagnosis:

• Sepsis
• Mechanical Failure
• Loosening secondary to malalignment, polyethylene wear, or instability
• Extensor mechanism problems secondary to instability, fracture, delamination, AVN, poly wear
• Implant failure
• Malalignment
• Instability
• Stiffness

Last Updated on January 24, 2026 by orthonet