When is it acceptable to fuse an ankle in slight equinus?

When is it acceptable to fuse an ankle in slight equinus?

• A. Good quadriceps strength
• B. Plantarflexion contracture
• C. Obesity
• D. Weak quadriceps muscles

Answer: (D)

The position is chosen to compensate for quadriceps weakness. When the quadriceps aren’t able to control the knee during stance, fusing the ankle in slight plantarflexion (a gentle equinus) reduces the knee extensor demand needed to keep the knee stable as the body progresses over the limb. This ankle position helps stabilize the knee by altering the tibial progression over the foot and providing a more favorable alignment during stance, making ambulation with a fused ankle more feasible and energy efficient. If the quadriceps are strong, or if the goal is to correct a plantarflexion contracture, or if other factors like obesity predominate, this ankle position would not be appropriate.