The unstable knee: wobble and buckle

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering

Background:

• Instability after total knee replacement (TKR) is a significant complication, necessitating revision in 10-22% of cases.
• Accurate diagnosis of TKR instability requires comprehensive patient history, physical examination, and advanced imaging.
• Deep periprosthetic joint infection must be excluded through laboratory tests and knee aspiration.

Purpose of the Study:

• To outline the diagnostic process for evaluating knee instability after total knee replacement.
• To categorize the primary types of post-TKR instability.
• To highlight the contributing factors and corrective surgical techniques for flexion instability.

Main Methods:

• Review of clinical presentation and diagnostic workup for TKR instability.
• Classification of instability into flexion, extension (symmetric/asymmetric), and genu recurvatum.
• Analysis of recent findings on flexion instability etiology and surgical management.

Main Results:

• Instability is a major cause of TKR revision, with specific diagnostic steps required.
• Three main instability types are identified: flexion, extension, and genu recurvatum.
• Flexion instability etiology and surgical correction strategies have been recently detailed.

Conclusions:

• Systematic evaluation is essential for diagnosing TKR instability.
• Understanding the different types of instability guides treatment.
• Surgical technique, alongside implant design and patient factors, plays a critical role in preventing and managing TKR instability.