Human patellar tendon strain. A noninvasive, in vivo study

Area of Science:

• Biomechanics
• Musculoskeletal research
• Human tendon properties

Background:

• The patellar tendon's mechanical properties are crucial for knee joint function.
• Previous studies often assumed tendon inextensibility, potentially underestimating in vivo strain.
• Understanding tendon strain is vital for injury prevention and rehabilitation.

Purpose of the Study:

• To challenge the assumption of patellar tendon inextensibility.
• To quantify in vivo patellar tendon strain during a low-load knee extensor task.
• To compare patellar tendon strain with values reported for other human tendons.

Main Methods:

• Utilized noninvasive, in vivo, three-dimensional cine phase contrast magnetic resonance imaging (PC-MRI).
• Measured velocity profiles of the patella, femur, and tibia in 18 healthy knees.
• Calculated patellar tendon elongation and strain from the imaging data.

Main Results:

• Demonstrated that the assumption of patellar tendon inextensibility is not valid.
• Observed higher strains in the patellar tendon compared to previously reported values for other human tendons.
• Recorded average maximum strains of 6.6% during a low-load knee extension task at small knee flexion angles.

Conclusions:

• The patellar tendon exhibits significant strain, invalidating the inextensibility assumption.
• In vivo patellar tendon strain is higher than often presumed, with implications for mechanical modeling.
• Findings highlight the need for accurate strain measurements in biomechanical analyses of the knee.