People around the world use running as a means to improve cardiovascular fitness, train for their chosen sport, or as a sport in itself. Patello-femoral pain syndrome (PFPS) or pain arising from the joint between the knee cap and thigh bone, is the most common injury seen in runners and affects up to 20% of the general population.
Locally, an imbalance between the quadricep muscles and abnormal tracking of the patellar contribute to the development of PFPS. The vastus lateralis and IT band pull the knee cap laterally, whereas the vastus medialis pulls the knee cap medially. Overactivity or tightness of the lateral structures or reduced/poor VMO strength causes the patellar to move laterally in its groove. During knee loading, abnormal alignment of the patellar increases the pressure in the joint, leading to anterior knee pain.
During the running cycle, the hip abductors such as the gluteus minimus and medius stabilise the hip and pelvis by preventing excessive hip adduction during loading of the lower limb. A 2008 study measured the hip abduction and external rotation strength pre and post run in runners with PFPS and healthy runners. Runners with PFPS recorded reduced hip abductor strength when compared with healthy runners, that lead to an increase in hip adduction during running (2). This increased hip adduction and therefore medial knee movement, is likely to contribute to mal-tracking of the patellar.
Running technique is another possible cause of PFPS. 75% of runners use a rear-foot strike pattern as they land, making contact with their heels (3). A heel strike pattern increases the vertical impact loading rate or the rate at which force travels up the leg when compared to a mid-foot strike (4,5). A rear foot strike pattern has also been associated with conditions such as plantar fasciitis (6), tibial stress fractures (7) and knee arthritis (8,9). It has been suggested that runners with a history of PFPS may exhibit higher vertical impact loading rates than healthy runners, possibly creating a link between foot strike pattern and PFPS (10).
Quadricep recruitment during the swing phase of running also increases in runners that land on their heels compared to a mid-foot strike pattern, increasing the force on the knee cap as they make contact with the ground. Because of these findings, a fore-foot or mid-foot striking pattern may reduce symptoms in patients with PFPS (11).
If PFPS is impacting your training and preparation for your next event, I recommend doing the following:
1. Stretch, foam roll and trigger your glutes, outside quadriceps and calves
– Ensuring optimal length of these tissues will help facilitate normal movement of the patellar and improve performance.
2. Gradually build your load
– slowly increasing your training volume will enable your body to adapt to the stress safely without putting you at risk. As a rule of thumb, increase your load by 10% every week
3. Strengthen your glutes
– Exercises such as side planks, glute bridges and theraband crab walks will help reduce excessive hip adduction as you run and provide hip/pelvic stability.
4. Increase your step rate and run quietly
– increasing your step rate as you run will cause you to use more of a mid-foot strike pattern. Trying to run quietly will also facilitate slower loading rates up the leg, allowing the muscles more time to react.
– Running shoes with a smaller heel require less work by the quadriceps and anterior shin muscles to clear the ground, reducing heel strike and therefore vertical impact loading rates. Make small changes to your footwear over time, as a dramatic change in shoe type is associated with an increased risk of injury.
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3 Hasegawa, H., Yamauchi, T. & Kraemer, W.J. (2007). Foot strike patterns of runners at the 15-km point during an elite-level half marathon. J Strength Cond Res, 21:888-893. http://dx.doi. org/10.1519/R-22096.1
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