Runners Knee – AKA patella femoral pain syndrome (PFPS) – Pain on or around the knee cap (part 1)
Patella femoral pain syndrome (PFPS) is consistently documented as the most common running injury. A study by Taunton et al (2002) documented running injuries in 2,002 runners over a 2 year period. PFPS was by far the most common with 16.5% of runners suffering with this condition.
Put very simply, your patella (knee cap) sits at the bottom of your femur (thigh bone) in a little groove, called the trochlea. When the knee flexes and extends, the patella runs in this groove a bit like a train runs on a track. Your patella is continuous with your quadriceps muscles (the muscles on the front of your thigh) and helps give the quadriceps muscle a mechanical advantage.
With PFPS, pain is usually felt on or around the knee cap. Painful activities typically include running, squatting, going up/down stairs, kneeling and sitting with the legs bent for a long time.
As you can see from the pictures, there’s lots of “stuff” (muscles, tendons, fat pads, bursa, ligaments, etc.) around this area and they all could be involved in the pain response… However, there are currently 3 main theories as to the tissue source:
- The patella femoral joint (PFJ) – Any translation of the patella (and this only has to be mm) on the femur, or excessive compression, can alter the pressure transmitted to the sub-chondrol bone, which is highly innervated (has lots of nerves).
- Peri-patella soft tissues (the muscles, ligaments, tendons, etc. around the kneecap). Increased stress/load on these areas can cause injury. It has been reported, that these tissues undergo angiogenesis (form new blood vessels) and neuronal ingrowth (form new nerves – similar to tendonopathy). It is hypothesised, that this constitutes a failed healing response and the subsequent pain is related to the neuronal ingrowth.
- Fat pad (highly innervated) – This can get pinched, which causes odema (swelling), this in turn changes the alignment of the patella, e.g. patella alta (patella being pushed upwards).
Now, this is the important bit from my point of view, knowing the tissue source involved in the pain state is helpful, I call this the “what?” of an injury, but I place much greater emphasis on the “why?”. The “why?” is the clinical reasoning behind it all. The question is: why is the joint/peri-patella soft tissues/fad pad injured or overloaded? We can argue and argue about where exactly the tissue source is…could it be the retinaculum?, the plica?, the medial patella facet? Trying to be 100% accurate is impossible. In my world the “why?” is much more important. Once we sort the “why?” out, the “what?” will take care of itself.
In part 2 of this blog (HERE) I will discuss how I commonly treat this condition in runners, including the common running patterns that I see and how to change your gait to improve symptoms…