Strain gauge analysis of knee ligaments

Area of Science:

• Orthopedics
• Biomechanics
• Sports Medicine

Background:

• Knee ligament injuries are common, impacting joint stability and function.
• Understanding ligamentous strain is crucial for effective treatment and rehabilitation.

Purpose of the Study:

• To quantitatively determine the relative strain of the tibial collateral ligament (TCL), anterior cruciate ligament (ACL), and posterior cruciate ligament (PCL) as a function of knee joint position.
• To provide insights into knee ligament injury patterns and optimal immobilization strategies.

Main Methods:

• Mercury strain gauges were sutured onto the TCL, ACL, and PCL of five human knee amputation specimens.
• Specimens were subjected to various forces (flexion, extension, rotation, valgus-varus, anteroposterior) to simulate physiological loading conditions.

Main Results:

• The TCL exhibits maximal laxity in full flexion and stretches with extension, valgus, and external rotation.
• The ACL and PCL are most lax at 35 degrees of flexion and are stretched by both flexion and extension.
• Internal rotation and varus forces specifically stretch the ACL.

Conclusions:

• Optimal immobilization positions to minimize ligamentous tension are identified: 35 degrees for ACL and PCL, and 45-90 degrees (or maximal tolerable flexion) for TCL.
• This knowledge enhances understanding of knee ligament injury mechanisms and informs post-injury or post-reconstruction management.