Patellofemoral pain syndrome (PFPS), also called runner’s knee, is characterised by pain between the patella (or kneecap) and the femur. Symptoms include pain while sitting with bent knees, running downhill, descending stairs or squatting.
PFPS should not be confused with patellar tendonitis which is characterised by pain in the tendon between the kneecap and your shin.
PFPS is usually caused by an important increase in your running mileage or repetitive stress on your patella. Some runners will experience pain due to repetitive compressive or shearing forces. PFPS is also associated with poor quadriceps development which causes the abnormal forces applied on your patella.
What does science have to say?
Scientists have studied PFPS very widely as it is the most common of all running injuries. Here are key facts:
- Diminution of impact force and loading rate is associated with a diminution of symptoms related to PFPS (1)
- Runners with history of PFPS exhibit a higher impact force and loading rate than healthy runners (2)
- Higher peak force and loading rates are predictors to PFPS (3)
- Direct relationship between step length and PFPS joint loads (4)
- Forefoot striker exhibit lower patellofemoral stress which may reduce the risk of knee injuries (5)
- Changes in Vertical Ground Reaction Force combined with appropriate training advice could explain the reduced pain and improved function of runners with PFPS (6)
- The reduction in vertical load rates may be protective for the knee and reduce the risk for other running-related injuries (7)
How to avoid it?
Researchers have demonstrated that high impact force and loading rate are key predictors to PFPS. Therefore, measuring are reducing impact force and loading rate should be your main focus to avoid runner’s knee.
Forefoot striking has also be proved to reduce knee stress in general. It may be an option if you have recurrent knee injuries. However, forefoot striking generates higher stress on metatarsal bones (i.e. your forefoot) and in Achilles tendon.
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