A recent 2023 study by Esculier, Bouyer and Roy showed immediate and significant changes in runners with kneecap pain when subjected to 6 different gait modification strategies. 

 

While there was plenty of biomechanical evidence to explain the changes in symptoms (due to changes in joint loading), some runners reported less pain despite increased loading on their joints. This seems counter intuitive. What could explain this? 

 

The authors mentioned that changes to the nervous system or a placebo effect may play a role in improving symptoms. This may explain why some participants responded to different movement patterns despite an increase in knee loading. There is speculation from the authors that this may be due to analgesic effects working on at the level of the brain and spinal cord. 

 

Fuel for this speculation is added by a February 2023 paper published by Eckenrode and colleagues. Here they examined the differences of pain sensitivity between runners with kneecap (patellofemoral) pain and pain-free runners. But pain is a subjective experience that varies for everyone, so how did the authors objectively measure this?

 

This issue was resolved by comparing each group’s pressure pain threshold values. A device called an algometer was placed on the shinbone (tibia), kneecap (patella) and thigh muscles (quadriceps) and squeezed pressure on those areas until the runner reported pain. The authors found that the amount of pressure needed to cause pain was significantly lower at all locations in the runners with knee pain. Additionally, it wasn’t only the symptomatic side that was affected, the non-symptomatic side was also more sensitive! 

 

From this, the authors concluded that the runners with persistent knee cap pain showed increased sensitivity to pain, both at “central” and “peripheral” levels. Central sensitization refers to a decreased threshold for cells in the brain and spinal cord to interpret pain. Peripheral sensitization refers to a decreased threshold for cells in other body parts to interpret pain. 

 

In bringing this concept back to Esculier’s paper, perhaps changing the running gait on someone with knee pain also changes how their brain and spinal cord interprets pain. It is truly difficult to parse the differences on which running variables are responsible for what, but this new research serves as an important reminder on the vital role in which the brain and nervous system play in our running and in pain.

 

References:

Esculier, J. F., Bouyer, L. J., &Roy, J. S. (2022). Running gait modifications can lead to immediate reductionsin patellofemoral pain. Frontiers inSports and Active Living, 4.

Eckenrode, B. J., Kietrys, D. M., Brown, A., Parrott, J. S., & Noehren, B.(2023). Signs of Nervous System Sensitization in Female Runners with Chronic Patellofemoral Pain. International Journal of Sports Physical Therapy, 18(1),132-144.