Over the past 20 years, the hip joint has been focused as a key injury predictor.
When the knee flexes, internally rotates and abducts during the first half of stance, the hip works in a similar fashion.
After heel strike and during the first third of the stance the hip flexes then undergoes almost full extension for the remaining two-thirds, until toe-off.
Comparatively, the hip does 3 to 4 times less internal rotation than the knee. External rotation of the hip starts at about 20% of the stance phase. Hip adduction then abduction happen with each phase.
Just like the relationship between the knee and the rearfoot, the hip and the knee work in an asynchronous way.
One of the reasons the knee gets injured so often at running is that both the knee and the ankle rotate faster and to a larger degree than the hip. The knee becomes a “logical” place of injury even under normal biomechanical circumstances, being in the middle and affected by any problem occurring downstream or upstream.
Next post we will talk about the potential impact of hip strength on runners.