Quadriceps Angle (Q-Angle) or Patellofemoral Angle
The Q-angle is defined as the angle between the quadriceps muscles (primarily the rectus femoris) and the patellar tendon. It represents the angle of quadriceps muscle force.
Q angle is the angle formed by a line drawn from the anterosuperior iliac spine of the hip bone to the central patella and a second line drawn from central patella to tibial tubercle.
Measurement:
The angle is obtained in supine or in standing. It must be ensured that the lower limbs are at a right angle to the line joining the two ASISs. To represent the gait stance phase better, the knee should be in 20° to 30° flexion so that the patella is more centralized in this position. A line is then drawn from the ASIS to the midpoint of the patella on the same side and from the tibial tubercle to the midpoint of the patella. The angle formed by the crossing of these two lines is called the Q-angle. The foot and the hip should be in neutral position as different foot and hip positions alter the Q-angle. Mechanisms that cause patellofemoral pain and athletic injuries have a stronger correlation with dynamic loading conditions and Dynamic Knee Valgus (DKV) assessment may be adopted in assessing athletic injuries.
Normally, The Q angle in males is typically between 8° and 14°, whereas that in females ranges from 11° to 20°.
The Q angle is measured using a universal manual Goniometer
Significance:
Q angle is used as an assessment parameter during the diagnosis of many knee-related problems, including the anterior knee pain, osteoarthritis, and degenerative knee disorders.
Reduced Q angle may be associated with chondromalacia patellae, patella alta, or patellar instability.
Q angle greater than 18° is often associated with PFPS, subluxing patella, increased femoral anteversion, genu Valgum, lateral displacement of tibial tubercle, or increased lateral tibial torsion.
Q angle and patella
In a normal knee, the line of force exerted by the quadriceps is lateral to the joint line. This is due to a larger force of vastus lateralis. The biomechanics of patellofemoral joint is influenced by the direction and magnitude of force exerted by quadriceps muscle. An increase the Q angle is thought to increase the lateral force on the patella. Thus, a high Q angle predisposes the patella to sublux laterally or dislocate over the femoral sulcus when the quadriceps muscle is activated on an extended knee.
A high Q angle increases the lateral patellofemoral contact pressures leading to increase the compression of the lateral patella on the lateral lip of the femoral sulcus.
Any reduction in the Q angle may not shift the patella medially, but could increase the medial tibiofemoral contact pressure by increasing the varus orientation.
Q angle and neuromuscular response
It has also been found that an abnormal Q angle may also influence neuromuscular response and quadriceps reflex response time. As a result, it may be a risk factor for anterior cruciate ligament injury.
Q angle in Females
Women have a greater value greater than that for men due to the wider pelvis, increased femoral anteversion, and a relative knee valgus angle
The higher Q angle values in females have put them at higher risk of patellofemoral pain as it increases the articulating surfaces compression.
Recent studies have found that high Q-angle values in females are also linked to the increase in cartilage thickness measurements of the medial femoral condyle and cartilage grading in female patients of osteoarthritis.
The greater Q angle values in females put them at risk of developing knee abnormalities
Q angle, gender, height and condylar distance
Researchers have proved that the Q angle was greater in females as compared to males.
Latest studies show significant negative correlation between Q-angle and height. The taller the person, the smaller the Q-angle value for that person, and vice versa.
Q angle increased remarkably when there was an increase in the condylar distance.
Effect of Q angle on athletes
With a wide Q-angle in females, there is more lateral movement of the patella as the quadriceps contracts. This predisposes the female runners to be at a greater risk for knee injuries than male runners. A larger Q-angle can also put women at a mechanical disadvantage while running.
An increase in the Q angle may also cause an increase in pressure between the patella and the underlying lateral femoral condyle when there is activation of the quadriceps muscle. This makes the Q angle to be a good predictor for knee injuries specially in sports with various jumping and landing.
Studies conducted on athletes on bilateral variability in the Q angle have documented variations in both legs of same individual. There are also documents showing insignificant increase in the dominant side of the Q angle. Researches report that these are not as significant as the variations between Q angles in right leg of male and right leg of a female and in left leg of male and a left leg of female. Thus, there is significant difference in the Q angles in male and female Athletes.
Factors affecting the Q angle includes Femoral anteversion, external tibial torsion, laterally displaced tibial tubercle and Genu Valgum.
Clinical application:
Your therapist can play a major role and help you to reduce Q-angle and thus prevent lateral displacement of patella. This is done by:
Strengthening either vastus medialis oblique (VMO)
Isometric quadriceps activation
Your therapist will guide you with the right choice of exercise in the management of patellofemoral pain and lateral displacement of patella.
We, at Valley Healing Hands are equipped with best physical therapists at Brownsville, Texas and will be happy to help you with your patellofemoral discomforts
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