Pain along the side of the abdomen, where the external oblique muscle is located, can range from a mild ache to sharp, intense discomfort that limits movement. While the external oblique is a common source of trouble, pain in this region can also originate from other systems. Understanding the muscle’s function and the various potential causes of discomfort is the first step toward finding relief.
Location and Role of the External Oblique
The external oblique (EO) muscle is the largest and most superficial of the three flat abdominal muscles, forming a significant portion of the side and front of the abdomen. It extends from the lower eight ribs, running diagonally downward and inward towards the midline, connecting to the pelvis and the central abdominal fascia.
The primary function of the external oblique is to facilitate trunk movement. Contraction on one side produces lateral flexion (side-bending) to the same side. Working with the internal oblique on the opposite side, it enables torso rotation.
The external oblique also plays a significant role in core stability and posture. It assists in increasing intra-abdominal pressure, which supports the spine during actions like coughing, forced exhalation, and heavy lifting. Injury can affect both movement and essential functions like deep breathing.
Primary Causes: Muscular Strain and Overuse
The most frequent cause of external oblique pain is a muscular injury, commonly called a “side strain.” This occurs when muscle fibers are overstretched or torn, typically due to sudden, forceful movements. Activities involving repetitive, high-velocity twisting or throwing motions, such as golf, tennis, baseball pitching, or rowing, often lead to this injury.
An acute strain usually presents as sudden, sharp, and localized pain on the side of the abdomen, often near the lower ribs. The pain intensifies immediately with movements that contract the muscle, including twisting, side-bending, coughing, sneezing, or deep breathing. Bruising, swelling, and stiffness (especially upon waking) may also be present.
Another common cause is overuse or delayed onset muscle soreness (DOMS), which follows a new or intense workout. Unlike a strain, DOMS pain is a dull, widespread ache that peaks 24 to 72 hours after exercise. Chronic, repetitive motions, such as heavy shoveling, raking leaves, or a prolonged bout of coughing, can also contribute to muscle fatigue and pain in the external oblique area.
When the Pain is Not Muscular
Pain felt in the external oblique area can sometimes be “referred” pain, meaning the source lies elsewhere in the body. Distinguishing a muscle issue from a systemic issue is important, as abdominal pain can imitate many acute and chronic conditions.
Pain referred from internal organs, particularly the urinary tract, can manifest near the external oblique in the flank area. Kidney stones, for example, cause severe, sharp pain that starts in the back and side, below the ribs, and often radiates to the lower abdomen and groin. This pain often comes in waves and may be accompanied by nausea, vomiting, or changes in urination, such as burning or blood in the urine.
Nerve pain, such as intercostal neuralgia, can present as sharp, burning, or shooting discomfort along the rib cage and upper abdomen. This condition involves irritation or damage to the intercostal nerves between the ribs. The pain may worsen with twisting, deep breathing, or coughing, similar to a muscle strain, but it may also include tingling, numbness, or a squeezing pressure sensation around the chest.
Another source of non-muscular pain is costochondritis, an inflammation of the cartilage connecting the ribs to the breastbone. Although typically felt in the front of the chest, the pain can sometimes be felt on the side. Like a strain, costochondritis pain is sharp and worsens with movement, deep breaths, or pressure on the chest.
Treatment, Recovery, and Medical Red Flags
For a mild external oblique muscle strain, conservative treatment focused on rest is effective. The initial step involves avoiding activities that caused the injury or increase the pain, allowing the muscle to heal. Applying ice to the painful area for 15 to 20 minutes every few hours during the first two or three days helps reduce swelling and discomfort.
Over-the-counter pain relievers, such as nonsteroidal anti-inflammatory drugs (NSAIDs), manage pain and inflammation. Once acute pain subsides, gentle stretching and strengthening exercises, often guided by a physical therapist, restore function and flexibility. Full recovery from an oblique strain can take a few weeks to a couple of months, depending on the severity.
Recognizing symptoms that require immediate medical attention is important to rule out serious conditions. Seek a medical evaluation if you experience severe, sudden-onset pain that is unbearable or prevents you from sitting still.
Red Flags Requiring Urgent Care
Pain accompanied by the following symptoms should prompt an urgent medical visit:
- High fever or chills.
- Persistent vomiting or signs of systemic illness.
- Blood in the urine or difficulty passing urine.
- Pain that radiates to the chest, neck, or shoulder.