In the vast majority of cases, cruralgia is due to compression of the crural nerve by a herniated disc. The hernia is a formation coming from an intervertebral disc, which, coming out of its normal space, puts pressure on one of the roots of the crural nerve.

The spine is formed by the stack of vertebrae separated from one another by a so-called intervertebral disc, a structure similar to that of cartilage and ligament. This disc normally acts as a shock absorber and force distributor. This disc, which has a ring with a core at its center, tends to dehydrate and crack over the years. The nucleus of the disc can then migrate to the periphery and protrude, and this is the herniated disc. This hernia can then irritate and compress a nerve root, in this case the lumbar root L3 or L4 for the crural nerve, and cause pain. This compression can also be linked to spinal osteoarthritis (parrot beaks, or bone formations compressing the root of the crural nerve) and / or a narrowing of the space of the spinal canal surrounding the spinal cord, which compresses it.

Much more rarely, other causes of compression can be considered (infection, hematoma, fracture, tumor, etc.).