A hernia develops when an internal organ or tissue pushes through a weak spot in the muscle or connective tissue that normally holds it in place. This happens through a combination of two forces: a weakness in the body’s containment wall and enough pressure to push tissue through that weakness. Sometimes the weak spot is something you’re born with. Other times, it forms gradually over years of strain, aging, or surgery.
How Hernias Actually Form
Think of your abdominal wall as a layered barrier of muscle and connective tissue keeping your organs in place. When that barrier has a thin spot, a gap, or a tear, the contents behind it can bulge outward. The bulge typically starts small and grows over time as the opening stretches and more tissue pushes through.
Your body has several natural weak points where hernias are most likely to appear. The groin, where muscles and ligaments form a canal, is the most common site. The navel is another, since it’s where the umbilical cord once passed through. The midline of the abdomen, where sheets of connective tissue join the left and right muscle groups, is also vulnerable. And any spot where a surgeon has cut through the abdominal wall becomes a permanent weak point.
Pressure: The Driving Force
A weak spot alone doesn’t always cause a hernia. It usually takes repeated or sustained pressure from inside the abdomen to force tissue through. That pressure can come from many sources, and it often builds up over months or years before a hernia becomes noticeable.
- Heavy lifting: When you lift something heavy, the natural pressure inside your abdomen spikes to help stabilize your spine. The more you lift, the higher that pressure rises, straining the abdominal wall. Repetitive strain can cause tissue to weaken and eventually tear.
- Chronic coughing: Conditions like COPD generate forceful, repeated coughing that hammers the abdominal wall from the inside. Over time, this can wear down tissue at weak points.
- Chronic constipation: Straining during bowel movements creates the same kind of internal pressure as heavy lifting. Done repeatedly over years, it can push tissue through a vulnerable area.
- Obesity: Carrying excess weight puts constant pressure on the abdominal wall, particularly around the navel and midline.
- Pregnancy: The expanding uterus stretches and thins the abdominal muscles, while the added weight increases intra-abdominal pressure. Umbilical hernias are especially common during pregnancy.
Even everyday actions like sneezing, coughing, or bending over can worsen an existing weak spot. You might not notice a hernia until one of these sudden pressure spikes makes a bulge visible for the first time.
Groin Hernias: The Most Common Type
Inguinal hernias, which occur in the groin, account for the majority of all hernias. About 27% of men will develop one in their lifetime, compared to roughly 3% of women. The reason for this gap is anatomical. During fetal development, the testicles descend from the abdomen through a channel called the inguinal canal into the scrotum. That channel is supposed to close after the testicles pass through, but it doesn’t always seal completely. This leftover opening creates a ready-made weak point.
There are two subtypes. An indirect inguinal hernia enters through the top of the inguinal canal, often because that fetal opening never fully closed. This is the type that can appear in infancy or childhood. A direct inguinal hernia pushes straight through the wall of the canal itself, developing in adults over time as muscles weaken and chronic pressure takes its toll. Direct hernias are most common in men over 50, and the cumulative prevalence in men climbs from about 5% in the 25 to 34 age group to 45% in men over 75.
Women can also develop groin hernias, though less frequently. Femoral hernias, which occur just below the groin crease near the upper thigh, are more common in women than in men.
Hiatal Hernias: A Different Location Entirely
Not all hernias involve the abdominal wall. A hiatal hernia occurs when part of the stomach pushes upward through the opening in the diaphragm where the esophagus passes through. A band of connective tissue normally keeps the junction between the esophagus and stomach anchored below the diaphragm, but aging loosens that tissue.
The sliding type accounts for up to 99% of hiatal hernias. It happens when the upper portion of the stomach slides symmetrically upward through the diaphragm opening. The less common paraesophageal type occurs when the stomach’s upper curve bulges through a widened opening beside the esophagus, while the junction itself stays in place.
Hiatal hernias become more common with age because muscle tone around the diaphragm opening decreases and connective tissue loses elasticity. When that tissue can no longer snap the stomach back into position after a swallow, the stomach gradually migrates upward. Anything that repeatedly spikes abdominal pressure, like heavy lifting, chronic coughing, or obesity, accelerates the process.
Why Previous Surgery Raises Your Risk
Any time a surgeon cuts through the abdominal wall, the repaired site never regains its original strength. About 10% of open abdominal surgeries result in an incisional hernia, where tissue bulges through the old surgical site. Midline incisions carry the highest risk at around 11%, while transverse (side-to-side) incisions drop to about 5%. Minimally invasive laparoscopic surgery brings the rate down dramatically to under 1%.
Older patients and those who develop wound infections after surgery face the highest odds. The hernia may not appear for months or even years after the original procedure, often becoming visible only when a sudden spike in pressure, like a sneeze or a heavy lift, pushes tissue through the weakened scar.
The Role of Genetics and Connective Tissue
Some people are simply built with weaker connective tissue than others, and genetics plays a meaningful role. Research has found that people who develop hernias tend to have an imbalanced ratio of the two main types of collagen that make up connective tissue. One type provides rigidity and strength, while the other is more flexible but weaker. When the balance shifts toward the weaker type, the tissue is less able to withstand pressure, making hernias more likely to form and more likely to recur after surgical repair.
This helps explain why hernias often run in families and why some people develop them without obvious heavy lifting or chronic straining. It also explains why certain individuals develop hernias at multiple sites or experience recurrence after surgery.
Age, Sex, and Who Gets Hernias Most
Hernias follow a distinctive pattern across the lifespan. In men, there’s a two-peak curve: one spike in the first year of life (from congenital openings that didn’t close) and another after age 40 as muscles weaken and collagen deteriorates. The lifetime prevalence in men is striking. Roughly 24 out of every 100 men will have or have had an inguinal hernia.
Women are more likely to develop ventral hernias, which occur along the front of the abdomen, particularly in their 50s. Pregnancy, C-section scars, and the broader shape of the female pelvis all contribute. While groin hernias are far less common in women, femoral hernias specifically are more prevalent in women than men.
In both sexes, the central theme is the same: aging weakens connective tissue while life accumulates the pressures, injuries, and surgeries that create or widen openings. By the time most people notice a hernia, the underlying weakness has likely been building for years.