Abstract
Background
The Q angle is an index of the vector of combined pull of the quadriceps and the patellar tendon. However, the Q angle is traditionally measured with the knee extended and static. The indexation of the Q angle measured using the traditional method therefore is questionable.
Questions/purposes
We asked if the Q angle would change when the knee flexed; if it did change, how it changed; and if it changed with different patterns in females and males.
Methods
We studied 30 volunteers' right lower extremities. To define the dynamic Q angle, we measured each volunteer's spatial position of the anterior superior iliac spine, patella center, tibial tuberosity, hip joint center, knee joint center, and ankle joint center. The Q angles were calculated with the knees at different angles of knee flexion.
Results
The Q angle was dynamic, and it was correlated with the knee flexion angle (P < 0.001). It decreased when the knee flexion angle increased and finally approached 0° when the flexion angle was larger than 90°. The dynamic Q angle in males and females had no significant difference (P = 0.066).
Conclusions
The Q angle is dynamic, and it approaches 0° when the knee is highly flexed. Additional studies are needed to further clarify the difference of Q angles in males and females.
