Q angle and knee pain

What is Q angle?

The Q angle describes the angle of the knee from a frontal view. The Q angle gives an idea how the thigh muscles functions to move the knee and also how the knee cap (patella) tracks in the groove of the knee joint. A normal knee cap should move up and down within the groove with flexion and extension of the knee. When the Q angle is excessive, the knee cap tends to track out of alignment and hence causes wear and tear (degeneration) of the cartilage behind the knee cap.

What is the normal Q angle?  The normal Q angle measured in standing is about 15 degrees and anything more than that is considered a risk factor for knee injuries. Ladies tend to have a wider Q angle due to their wider pelvis compared to their males.

Q angle
Q-angle

How to measure Q angle? The Q angle is an intersection of two lines. First line joins the ASIS (bony protrusion in the front of the pelvis) to the middle of the patella. Second line runs from the protrusion on the top of the shin bone (tibial tuberosity) below the patella and upwards through the middle of the knee cap.

Common injuries related to a wide Q angle:

  1. Iliotibial band friction syndrome (ITBFS)
  2. Anterior knee pain or Patella Femoral Pain Syndrome (PFPS)
  3. Anterior cruciate ligament injury (ACL)

Injuries because of an excessive Q angle can be categorised into 3 main reasons.

1. Muscle imbalance :

A large Q angle pulls the knee cap outwards due to the stronger lateral pull from the quadriceps and tight ITB. Coupled with a weakness of the inner aspect of the quadriceps (Vastus Medialis Oblique, VMO) the knee cap will track laterally instead of smoothly up and down within the knee groove. This maltracking causes the cartilage behind the knee to wear off or degenerate and hence the pain.

2. Biomechanical compensation:

An excessive Q angle can alter the movement pattern especially in the foot. The knee will tend to point inwards (valgus or knock-knee appearance) which encourages the foot to roll inwards (pronates). Over-pronation can lead to a number of injuries especially in runners.

3. Joint laxity/instability:

When the knee point inwards, the ligaments on the inner aspect of the knee gets overstretched and lax, therefore compromising the stability of the knee joint. The Anterior Cruciate Ligament (ACL) also undergoes a lot of stress in this position. Interestingly the larger Q angle in females has been attributed as a main reason why females are at a higher risk of sustaining an ACL injury.

How to manage a wide Q-angle?

You can reduce the risk of injuries by targeting the reasons above.

Muscle imbalance: Stretching on the ITB, strengthening the VMO and Glut medius to enable proper tracking of the knee cap.

Biomechanics: Get a customised orthotics to control excessive pronation and reduce the stress to the knee.

Joint Laxity/Stability: Balancing exercises to train knee proprioception and stability.

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