Dynamic Knee Alignment and Collateral Knee Laxity and Its Variations in Normal Humans

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Medical Imaging

Background:

• Knee alignment and collateral ligamentous laxity are critical in orthopedic surgery, with traditional quantitative values frequently debated.
• Existing measurement methods for knee alignment and laxity have known limitations and inaccuracies.

Purpose of the Study:

• To review current literature on human knee alignment and collateral laxity.
• To introduce and evaluate a novel method for measuring knee alignment and laxity using computer navigation in a clinical setting.
• To challenge the conventional understanding of knee alignment, particularly the concept of a straight mechanical axis in normal knees.

Main Methods:

• A comprehensive review of recent scientific literature on knee alignment and collateral laxity.
• Implementation of a novel computer navigation technique for pre-operative assessment of knee alignment and laxity in a clinical setting.
• Analysis of alignment changes from non-weight-bearing to weight-bearing positions in both coronal and sagittal planes.

Main Results:

• Normal knees exhibit a mean varus alignment, contradicting the myth of a straight mechanical axis.
• Knee alignment significantly changes between non-weight-bearing and weight-bearing positions.
• Collateral knee laxity demonstrates variations based on gender and race, with differences noted between males and females.

Conclusions:

• The study dispels the myth of a straight mechanical axis in normal knees, highlighting a mean varus alignment.
• Knee alignment and collateral laxity are dynamic and influenced by patient-specific factors like position, gender, and race.
• Further research is essential to establish ideal alignment parameters and collateral laxity targets for individual knee surgeries.