Other issues, such as arthritis or pain in the psoas muscle (which helps flex the hip joint), can cause similar symptoms.

For instance, lung cancer that spreads to the psoas muscle—a long, ribbon-shaped muscle on either side of the lower spine—may cause lower back pain. Soft tissue metastasis is often a sign of ...

The iliacus is a key part of the larger and better-known hip flexor (the other main muscle being the psoas). Together, the iliacus and the psoas make up the hip muscle group that connects the ...