Final answer:
The gait disorder commonly associated with a ruptured lumbar disc is ankle dorsiflexor weakness. This weakness leads to a high-stepping walk or steppage gait, where patients lift their knees higher than normal to avoid dragging their toes.
Step-by-step explanation:
A common gait disorder associated with a ruptured lumbar disc is ankle dorsiflexor weakness, which can lead to a steppage gait if severe. When the lumbar disc herniates, it can compress the spinal nerve root that innervates the muscles responsible for dorsiflexion of the ankle. As a result, patients may have difficulty lifting the front part of their foot and toes off the ground when walking, which results in a high-stepping type of walk to prevent the toes from dragging on the ground. This can be contrasted with other types of gait disorders, such as a waddling gait that is typically seen with proximal muscle weakness (e.g., in muscular dystrophies), or weakness in the triceps surae group or the ankle plantar flexors, which result in different walking abnormalities.