Does a greater Q angle cause Patellofemoral Pain Syndrome?
Running is an extremely popular sport across the globe; however, it comes with a high injury rate. Over 70% or runners report an injury each year, with one of the main problems being Patellofemoral Pain Syndrome (1). PFPS is often characterised as pain around or under the kneecap (2) and often becomes chronic for runners that experience it which can have a detrimental effect on health and performance.
As a result, there have been several studies looking into the cause of PFPS in the hope that there are ways that runners can avoid the debilitating injury. One of the main suggestions is that abnormal hip and knee mechanics are associated with PFPS and specifically the degree of the Q angle.
The Q angle is the angle between the line connecting the anterior superior iliac spine (ASIS) to the centre of the patella, and the extension of a line from the tibial tubercle to the same reference point on the patella (3). Women usually have a greater Q angle than men due to the size of their hips in comparison. Women are also more susceptible to running related knee injuries. Commonly an angle greater than 15 degrees for men and 20 degrees for women is classes as abnormal (4) and it has been suggested that a high Q-angle could be a risk factor for lower-limb overuse injuries, in particular Patellofemoral Pain Syndrome (PFPS) (5).
The possible theory behind a greater Q angle causing PFPS is that it increases the lateral pull of the quadriceps muscles on the patella and this places medial tensile stress on the soft tissue at the knee (6). This increased pull might lead to extra pressure on the lateral facet and cause knee pain. However, currently many studies have suggested that a greater Q angle does not correlate with PFPS in runners.
In a study of 282 students in physical education classes, they found over a two-year period 24 students developed PFPS. The findings showed that the Q angle was not associated with PFPS and instead muscle flexibility, joint laxity and reflex response time of the vastus medialis, obligus and vastus lateralis muscles did correlate with the pain. (7) Further studies by Lun et al measured the static lower limb alignment of 87 recreational runners and monitored their injuries over 6 months. Again, there was no strong evidence that lower limb alignment and PFPS had any correlation.
Another theory as to why a greater Q angle might cause PFPS is due to how it affects knee alignment in the frontal plane. It has been suggested that knee abduction impulse is a good indicator of twisting loads on the knee in the frontal plane and the impulse might be related to the development of PFPS. Studies have shown that PFPS patients show greater knee abduction impulses compared to non-injured runners. The Q angle affects the alignment; however, no research so far has shown that this then is associated with PFPS. In a study to test this, there proved to be a negative correlations with the Q angle and the magnitude of peak abduction moment and further negative correlations between Q angle and the magnitude of weight normalised knee abduction moment (8). Although a greater Q angle might alter the alignment of the knee at the frontal plane, there is not yet any evidence to suggest that it causes PFPS or any other running related overuse injury.
With the study above relating to alignment in the frontal plane, the mean Q angle degrees were 12.9 degrees in males and 16.4 degrees in females. As stated earlier, a Q angle greater than 15 degrees in men and 20 degrees in women is classed as abnormal therefore the average range in this study has not highlighted whether an abnormal Q angle would have the potential to cause PFPS. More studies need to be investigated looking at the extreme end of the Q angle and whether they have an effect of PFPS. Likewise, there is scope to look into whether or not a female and male runners at the greater end of the Q angle have the same outcomes in terms of joint alignment and whether or not it has a correlation with overuse running injuries.
Unfortunately, PFPS and other overuse injuries are still prevalent amongst the running community and so far, there is no one definite way of reducing the chance of injury. So far evidence suggests that a greater Q angle does not correlate with PFPS and other knee related injuries. However, more studies can be done to look at the ‘abnormal’ range of Q angles in men and women to determine whether these do cause pain when running.