The sternum, or breastbone, is the flat bone where the ribs meet. Sometimes, the joints can pop or crack as a person stretches or moves. A muscle spasm, an injury, costochondritis, and surgery are ...

When a person cracks their back, the sudden movement causes air pockets in the synovial fluid of the joints to react with a popping or cracking noise. Although cracking the back may feel good, it can ...