If your shoulder pops or cracks when you do exercises such as pushups, escaping gases or tendon slippage may be the cause. The structure of a joint plays a part in creating the popping sound, also called an “audible release.” The fluid that lubricates and nourishes the joint and its soft tissues contributes to the cracking. Cracking and popping is not generally considered harmful to joints, but in certain circumstances it might indicate a problem.
The fluid that lubricates your joints contains three gases: carbon dioxide, oxygen and nitrogen. When you do a pushup, you may be creating negative pressure in the shoulder joint. This allows the gases to escape the synovial fluid and form a bubble. This escaping gas creates a cracking or popping sound. This sound can happen multiple times, as long as the gases have time to collect in the synovial fluid again.
When you do a pushup, you may be stretching your shoulder joint beyond its normal range of motion. This movement can result in cracking or popping noises. Dr. Stacey Burke of West Coast Family Chiropractic suggests that the health benefits to increasing range of motion far outweigh any concerns about the popping noises that may occur.
One cause of a joint cracking or popping may be due to a tendon snapping in and out of place as the joint is moved. According to an article published on the Johns Hopkins Orthopedic Surgery website, there is no definitive evidence of the cause of joint-cracking noises, though x-rays taken during joint-cracking do show nitrogen bubbles forming.
Popping and Arthritis
Common sense might make you think that a popping or cracking sound when you do a pushup is signaling a potential problem. For example, some people think joint-cracking leads to arthritis. According to an article published in 2001 in "Scientific American": "There are actually few scientific data available on this topic. One study found no correlation between knuckle cracking and osteoarthritis in the finger joints. Another study, however, showed that repetitive knuckle cracking may affect the soft tissue surrounding the joint. Also, the habit tends to cause an increase in hand swelling and a decrease in the grip strength of the hand." If you are concerned about your shoulders popping, ask your doctor for her opinion.
Popping and cracking noises in the absence of pain is usually nothing to worry about, according to the Library of Congress Science Reference Services. If your shoulder pops during a pushup and you experience pain, consult your doctor. Although the noise itself is not an indication that anything is wrong, swollen joints, loss of range of motion or loss of function when popping occurs may be a sign of a joint problem.