Costochondritis is usually caused by inflammation where your ribs meet the cartilage near the breastbone, but in many people no single clear trigger is ever found.

Main medical causes

  • Idiopathic (no clear cause) : In most cases, doctors cannot identify a specific reason; the joints simply become inflamed without a clear injury or illness, which is why costochondritis is often called idiopathic.
  • Chest injury or trauma: A direct blow to the chest (for example, from a fall or car accident) can irritate the costochondral joints and trigger inflammation.
  • Repetitive strain and overuse: Heavy lifting, strenuous upper‑body workouts, certain sports, or work that involves repeated pushing, pulling, or twisting of the upper body can lead to repeated microtrauma in the rib joints.
  • Severe or prolonged coughing: Long bouts of coughing from infections (like a bad cold, bronchitis, or COVID‑19) or chronic lung problems create repeated strain on the chest wall and are a well‑recognized trigger.

Less common underlying factors

  • Infections: Bacterial, fungal, or other infections can rarely spread to the costosternal joints and cause painful inflammation, especially in people with weakened immune systems or after chest surgery.
  • Rheumatologic and inflammatory diseases: Conditions such as rheumatoid arthritis, seronegative spondyloarthropathies, or other inflammatory musculoskeletal disorders can involve the chest wall and present as costochondritis‑like pain.
  • Spine and posture problems: Issues with the joints in the upper back or poor posture can change how forces load the ribs and sternum, contributing to mechanical stress and pain in the costochondral joints.
  • Tumors or post‑radiation changes (rare): Benign or malignant chest wall tumors and prior radiation to the chest can occasionally irritate or damage the costal cartilage and mimic or cause costochondral pain.

How doctors think about it

  • Local inflammation: The core problem is thought to be localized inflammation of the costochondral or costosternal joints, which makes them tender and painful when pressed or moved.
  • Microtrauma and mechanics: Repetitive small stresses, muscle imbalance, or altered movement around the ribs and sternum may gradually overload these joints and provoke pain, even without a single “big” injury.
  • Overlap with other conditions: Costochondritis can look similar to heart, lung, or gastrointestinal problems, so clinicians first rule out dangerous causes of chest pain before settling on this musculoskeletal diagnosis.

Information gathered from public forums or data available on the internet and portrayed here.