What is the Q angle?
The Q angle is an important predictor of biomechanical abnormality throughout the lower limb. It is a measurement of the angle between the Quadriceps (Rectus Femoris is usually used) and the patella tendon. This provides useful information about the alignment of the knee joint, which if outside of normal ranges, can be a precursor for overuse injuries.
How do you measure the Q angle?
You will need a long-arm goniometer. The Q angle can be measured in laying or standing. Standing is usually more suitable, due to the normal weight-bearing forces being applied to the knee joint as occurs during daily activity.
Place the centre of the goniometer over the centre of the patella and position the bottom arm in line with the patella tendon and tibial tuberosity. Next position the upper arm so that it is pointed directly at the anterior superior iliac spine (ASIS) of the ilium (point to which rectus femoris attaches). The small angle of the goniometer is the Q angle.
What is a normal Q angle?
A normal range for the Q angle in standing is between 18 and 22 degrees. Women are usually at the higher end of the range due to their naturally wider pelvis. If measured laying down the angle will be 1-3 degrees lower.
A high Q angle often results in mal tracking of the patella, that is it does not travel over the front of the knee joint as it should. Overtime this can cause microtrauma to the cartilage on the rear of the patella which causes pain, often known as anterior knee pain, patellofemoral pain or chondromalacia patella.
Having over-pronated feet also places additional strain on the Q angle due to excessive internal rotation of the tibia.
How do you decrease the Q angle?
A thorough biomechanical assessment is required in order to progress with a treatment plan. The first step is to correct any over-pronation at the feet using orthotics.
There is no manipulation or adjustment (such as you might receive at a chiropractor) to reduce Q angle. Correct biomechanics must be achieved through a rehabilitation program which focuses on restoring flexibility to tight muscles (commonly calves, hamstrings and quadriceps.
Weaker muscles must also be strengthened. It is common that laterally positioned fibres of the Vastus medialis known as VMO (vastus medialis oblique) are weak. These fibres also play an important role in controlling the stability and positioning of the patella and so strength and timing of contractions should be restored.
This can be achieved by placing a rolled up towel under the knee (whilst sitting) so that it is slightly flexed. Whilst palpating VMO push the knee down into the towel so that it straightens and the heel rises from the floor. You should feel the muscle fibres under your fingers contract.
Once this is mastered half squats against a wall or fit-ball can be introduced, still maintaining contraction of the VMO.
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