What is the primary symptom that denotes acute locked back due to facet entrapment?

The primary symptom of acute locked back due to facet entrapment is localized low back pain. This condition arises when a facet joint in the spine becomes misaligned or trapped, leading to significant pain and reduced mobility in the affected area. Patients often describe a sudden onset of sharp, localized pain in the lower back, which may be exacerbated by certain movements or positions.

In addition to the pain, individuals may experience muscle spasms and stiffness in the lumbar region, making it difficult to move comfortably. The exact mechanism involves the joint surfaces of the facet joints not being able to glide properly due to the entrapment, which is why the pain is focused in the local area rather than radiating into other regions, like the legs.

Other symptoms, such as radiating pain down the leg or neuropathy, are more indicative of conditions like sciatica or herniated discs, which involve nerve root irritation or compression. Limitation in hip flexion may occur, but it is not a primary symptom associated directly with facet entrapment. Instead, the hallmark of locked back due to facet entrapment is distinctly characterized by that localized low back pain.