The angle formed by the line of traction of the quadriceps tendon on the patella and the line of traction of the patellar tendon on the tibial tubercle. The area is usually larger in women than in men.
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The influence of Q-angle and gender on the stair-climbing kinetics and kinematics of the knee (dissertation).
patella alta, increased Q-angle with lateral position of the tibial tuberosity, genu valgum, ligamentous hyperlaxity, vastus medialis muscle hypoplasia, external tibial torsion, subtalar joint pronation and increased femoral anteversion.
The quadriceps angle, or Q-angle, is defined as the angle formed by the intersection of two lines, one that starts at the anterior iliac spine and goes to the center of the patella, and another that goes from the tibial tuberosity to the center of the patella.
Guerra J, Arnold M, Gajdosik R, 1994, Q-angle: effects of isometric quadriceps contraction and body position.
They suggested that acute lateral patellar dislocation may indicate a tear of the MPFL associated with concomitant injury of the MCL and both the MPFL and MCL should be managed operatively because isolated MPFL reconstruction often fails due to a persistent increase in the Q-angle. In our case, both the MCL injury and patellar dislocation were likely caused by the same injury, and MCL injury caused the dynamic increase in Q-angle and acted as an adjunctive patellar destabilizer.
In the study, the Q-angle was different between injured and non-injured runners.
On average, females have a larger quadriceps angle (Q-angle) than males (Charlton, Charlton, & Ciccotti, 2001).
Knee pain is a problem that can be experienced due to many contributing factors, including: increased Q-angle, genu-valgum and genu varum, muscle tightening through the gastrocnemius, lliotibial band and VMOs, hyperextension of the knee and tibial rotation and torsion.
Women's knees have an extra Q-angle, and that has been shown to be a factor," McLaine says.
We used regression techniques to determine if anthropometric factors (BMI, navicular drop, Q-angle) and lower-extremity muscle strength contributed to observed differences in landing movements.
Several factors have been proposed to cause patellofemoral pain syndrome such as patellar malalignment (Fredericson and Yoon 2006, Powers 2003), an increased Q-angle (Elias et al 2004, Fredericson and Yoon 2006, Mizuno et al 2001, Naslund et al 2006), quadriceps weakness (Fredericson and Yoon 2006, Thomee et al 1995), decreased flexibility of the lower extremity (Fredericson and Yoon 2006, Piva et al 2005), overuse (Thomee et al 1999), and muscle imbalance (Thomee et al 1995) which have all been shown to result in an increase in cartilage and subchondral bone stress (Fredericson and Yoon 2006).
On physical examination, check for the quadriceps angle, or Q-angle, which is the angle created between a line drawn from the center of the anterior superior iliac spine on the pelvis to the center of the patella and a second line from the center of the patella to the middle of the tibial tubercle.