Quite a while ago, Conrad and Benecke found that 81% of patients with lumbar disc herniation and L5 nerve irritation had reduced gluteus medius innervation. The gluteus medius muscle is primarily responsible for hip abduction (raising the leg away from the body while lying on the side). Note that this L5 nerve root also provides innervation to the muscles involved in dorsiflexion. So if you think of it as a garden hose, we can use clinical tests to determine where compression occurs along the length of the garden hose. Does it happen at the nerve root, where it exits the spine, or does it happen further down, just below the knee, where the fibular nerve is sensitive? If the patient shows obvious strength and skill in the gluteus medius, the nerve root (near the spine) is probably not the cause. In other words, if the patient has foot drop and a fast gait with a strong gluteus medius, the entrapment is more likely to be lower. If the patient has foot drop but also gluteus medius weakness, it may be more reasonable to expect the problem to be closer to the spine. As mentioned above, this would suggest causes such as spinal stenosis or lumbar herniated disc.
If you’re not a practitioner, it’s entirely reasonable to be a little confused right now. The important message of this blog is that if you have foot drop, there is a lot you can do from a treatment standpoint. Obviously, a foot drop treatment strategy is more likely to help if we have a better idea of where the problem lies. Nerve conduction tests can be helpful in determining where the nerve entrapment is occurring, but there is often a long waiting list to do so.
When does peroneal nerve palsy occur?
Normally, movement impulses are sent from the brain to the spinal cord, from where the impulses reach the neural pathways. If this process is interrupted at any time, the pulses cannot be transmitted and processed correctly.
In case of foot drop, the peroneal nerve is affected. This extends from the thigh to the knee, where it divides into two branches that extend to the foot. The actual restriction of the nerve can come from the leg itself or from the spine or the brain. If there is paralysis or nerve damage, the brain impulses that are supposed to raise the leg so a person can walk are not transmitted correctly. This leads to the typical driving problems.