Three-dimensional patellar motion at the natural knee during passive flexion/extension. An in vitro study

Area of Science:

• Orthopedics
• Biomechanics
• Biomedical Engineering

Background:

• Patellar maltracking is linked to various patellofemoral joint (PFJ) disorders.
• Limited quantitative data exists for normal PFJ kinematics, hindering maltracking identification.

Purpose of the Study:

• To accurately measure in vitro all six degrees of freedom of patellar motion relative to the femur and tibia in normal knees.
• To establish quantitative references for normal PFJ kinematics.

Main Methods:

• Utilized a state-of-the-art knee navigation system adapted for PFJ analysis.
• Defined anatomical reference frames for femur, tibia, and patella per international standards.
• Calculated PFJ flexion, tilt, rotation, and translations alongside tibiofemoral joint (TFJ) kinematics.

Main Results:

• Demonstrated repeatable patellar motion patterns intra- and inter-specimens.
• PFJ flexion averaged 62% of the TFJ flexion range.
• Observed average tilt and translations within 12 degrees, 6 mm, and 9 mm, respectively, with specific directional trends.
• No consistent pattern was identified for PFJ rotation.

Conclusions:

• The study provides consistent, quantitative data on normal PFJ kinematics.
• Findings contribute to understanding knee biomechanics and orthopedic treatments.
• The data can aid in identifying patellar maltracking and inform intraoperative measurements.