Chronic knee pain in runners: how much is in the mind?

Ask any runner and they’ll tell you that knee pain and injuries are the bane of a consistent training schedule. While overuse injuries of the lower extremities are common in runners, patellofemoral knee pain (PFP) is reported as the most frequently occurring condition⁽¹⁾. PFP is defined as a knee condition that causes pain beneath or around the kneecap, which can occur during activities such as running, walking kneeling and squatting. Typically, PFP sufferers also experience pain under the kneecap after maintaining a sitting position for a period of time or when kneeling, and in acute cases, there may also be swelling present.

What causes PFP and who is at risk?

There are a number of theories as to why runners develop PFP, many of which involve weak or unbalanced musculature, which can lead to altered biomechanics. Commonly cited causes include tight hamstrings and Achilles tendons, inadequate arch support and excessive pronation (inwards rolling of the ankle following footstrike)⁽²⁾. However, other factors are undoubtedly also involved including motor performance deficits, poor shoe choice and overtraining⁽³⁾. Regardless of the cause however, PFP can often become chronic and persistent, with up to 91% of individuals reporting continued pain 4-18 years after the initial diagnosis⁽⁴⁾!

Another relevant fact about chronic PFP is that it’s twice as prevalent in female runners compared to male runners⁽⁵⁾. This is most likely due to the differing anatomy between males and females; on a height for height basis, the female pelvis is wider than the male pelvis, resulting in a larger ‘Q-angle’ of the lower limbs. The Q-angle is defined as the difference from vertical when a straight line is drawn from the outer edge of the pelvis (anterior superior iliac spine) through the midpoint of the patella (kneecap) – see figure 1. The wider the pelvis in relation to height, the greater the Q-angle, and therefore the greater the torsional stresses transmitted through the knee.

Figure 1: The Q-angle