Which of the following conditions may indicate a rigid Pes Planus during assessment?

A rigid Pes Planus, or flatfoot, is characterized by a persistent flattening of the foot arch that does not recover its height when weight is applied. This condition can lead to various biomechanical issues and discomfort. When assessing for rigid Pes Planus, the critical factor is observing how the arch behaves under different conditions.

The option that states the arch flattens and does not return signifies that there is a lack of elasticity or flexibility in the structures of the foot. This characteristic is a defining trait of a rigid condition, as the foot cannot regain its normal shape after weight-bearing activities.

In contrast, the other options describe different conditions: the arch remaining elevated suggests normal arch function, while the arch that appears and then flattens when weight-bearing indicates a flexible or mobile Pes Planus. The scenario where the arch functions normally under all conditions clearly points to a healthy arch structure. Thus, the condition indicating a rigid Pes Planus is aptly captured by the option regarding the arch flattening and not returning, distinguishing it from more flexible presentations.