Internal Oblique: Definition, Location & Function

Instructor: Alexandra Unfried

Alexandra earned her master's degree in nursing education and is currently a hospital supervisor/administrator.

The internal oblique is a part of a group of abdominal muscles that help support the abdominal wall. This lesson will define the internal oblique muscle and discuss the location and function.

Why is there Pain in the Rib Cage?

Mark is a golfer who has developed a sharp pain around his rib cage, especially when twisting his upper body to the left. He has also noticed some bruising and tenderness in the same area. Mark is now wondering what he has injured and how it will affect his daily life.

Internal Oblique: Definition

In his research, Mark finds out that there are four sets of muscles that make up the abdominal muscles. They are the rectus abdominis, the transverse abdominis, the external obliques, and the internal obliques. There are two sets of internal oblique muscles that are located on each side of the body. They are below the rectus abdominis and just inside the hip bones. The internal obliques control the movement on the same side of the body. This means that if Mark twists to right, the right side internal obliques are contracting. Therefore, they are sometimes referred to as 'same side rotators'.

Location of internal obliques

Mark is realizing that since he has pain when twisting his upper body, he may have injured one of his abdominal muscles. He needs to understand where the muscles are located in order to figure out which muscle is injured.

Internal Oblique: Location

The internal oblique begins at the lumbar fascia, the outer two-thirds of the inguinal ligament, and the front two-thirds of the iliac crest. The lumbar fascia is a connective tissue that covers the lower back. The inguinal ligament is a ligament located on the bottom-outer edge of the pelvis. The iliac crest is the upper-outside portion of the pelvis.

The internal oblique ends at the costal margin, aponeurosis of the rectus sheath, and the connected tendon to the pubic crest and pectineal line. The costal margin is located at the bottom on the rib cage. The aponeurosis is a fibrous tissue covering the rectus sheath, which is where the abdominal muscles come together. The pubic crest is the lower front of the pelvis.

Location of iliac crest, inguinal ligament, and pubic crest

Therefore, pain felt in the ribs is often caused by an injury to the internal obliques because they are attached to the bottom of the rib cage. Mark identifies that the pain he is feeling is probably caused by a strain to his internal oblique on the left side of his abdomen. This was most likely triggered by the twisting motion that he does with his body when he swings his golf club.

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