A fusion of the subtalar joint affects which joints during gait?

When the subtalar joint undergoes fusion, it significantly impacts foot mechanics and thereby affects several joints during gait. The correct option reflects the interrelatedness of the kinetic chain in lower extremity movement.

The subtalar joint is crucial for pronation and supination of the foot, which in turn influences how the foot interacts with the ground and how forces are transferred up the leg. If the subtalar joint is fused, the foot loses its ability to adapt to various surfaces and absorb shock effectively. This rigidity can lead to altered gait patterns that affect both the hip and knee joints, as they rely on foot positioning for optimal alignment and movement.

In contrast, while the ankle joint is closely linked to the subtalar joint mechanics, it may not experience the same level of functional compromise in terms of kinetic chain dynamics as the hip and knee, which have to compensate for a more stable foot structure. Similarly, the mid-tarsal joint and calcaneal cuboid joint are also affected by subtalar function, yet the most significant compensatory adjustments typically occur at the hip and knee levels.

Therefore, recognizing the integration of movements throughout the lower limb helps explain why the hip and knee joints are primarily affected by the subtalar fusion in the context of gait.