A marathon runner with rigid cavus feet experiences knee pain after wearing custom orthotics. What might be the issue?

The situation described involves a marathon runner with rigid cavus feet who experiences knee pain after using custom orthotics. The correct assertion that the orthotics may be "too hard" indicates that the materials or design of the orthotics fail to provide adequate shock absorption and cushioning for the runner’s foot type.

Runners with rigid cavus feet typically have an increased arch height, which can lead to reduced shock-absorbing capabilities during high-impact activities like running. When the orthotics are too firm or hard, they can fail to accommodate the foot's inherent biomechanics, consequently transmitting excessive forces to the knee and other joints. This can result in discomfort or pain in the knee due to the lack of appropriate cushioning and support.

In the context of rigid cavus feet, it is crucial for orthotics to provide sufficient support while also allowing some degree of cushioning to mitigate impact forces. If the material is too hard, it cannot effectively absorb the stress placed on the foot during running, leading to improper mechanics and potential injury in the lower extremities, including the knees.

Other factors, such as the softness or length of the orthotics or subtalar joint control, could also play a role in comfort and function, but in this case, the excess rigidity of