A click, pop, or slight grinding sensation from a baby’s shoulder can be alarming. This phenomenon, medically termed crepitus, is the sound produced by joint movement. In the vast majority of cases, these noises are harmless and non-painful for the infant. A baby’s joints are naturally more flexible and less developed than an adult’s, contributing to the frequency of these audible events. If your child is happy and moving their arm freely, the sound is usually a normal part of physical development.
Common Reasons for Benign Clicking
The most frequent cause for a painless joint pop is joint cavitation. This involves the formation and sudden collapse of gas bubbles (nitrogen, oxygen, and carbon dioxide) within the synovial fluid that lubricates the joint. This mechanism is identical to the sound produced when an adult cracks their knuckles and carries no medical significance. The bubbles release when the joint is rapidly moved, momentarily changing the pressure within the joint capsule.
Infants are born with ligament and tendon laxity, meaning the connective tissues surrounding the joints are softer and more pliable. This natural elasticity allows tendons to momentarily snap or slip over a bony prominence during movement. Since the baby’s skeleton is still largely made of soft, developing cartilage, the joints are less constrained, making these slight movements more common. This slipping is a benign mechanical event that usually resolves as the baby grows and their soft tissues tighten and strengthen.
The developing nature of the infant’s skeletal structure also contributes to noise production. Unlike adult joints, the shoulder surfaces are still maturing, and the surrounding structures are hypermobile. This greater flexibility translates into more frequent and audible sounds during motion. If the clicking is not associated with discomfort or restricted movement, it is simply a byproduct of this normal growth.
Medical Conditions That Cause Shoulder Noise
While most shoulder noises are benign, a crunching sound can signal an underlying medical issue, especially if it occurs shortly after birth. A clavicle fracture (broken collarbone) is a common birth injury, often following a difficult delivery or shoulder dystocia. The sound associated with this condition is typically a true crepitus—a grating or crunching noise—accompanied by clear signs of pain and limited mobility.
A brachial plexus injury, often called Erb’s palsy, involves damage to the network of nerves running from the neck to the arm. This nerve damage causes muscle weakness or paralysis. The resulting flaccidity can lead to joint instability that may occasionally produce a popping sensation. However, the defining symptom is the inability to move the affected arm, which may hang limp at the baby’s side.
Shoulder instability or true dislocation in a newborn is rare. A genuine dislocation involves the ball of the joint coming out of its socket, causing immediate, severe pain and a visible deformity. Any popping sound related to instability would be consistently painful and accompanied by a significantly limited range of motion, requiring prompt orthopedic assessment. These serious conditions are always distinguished from benign crepitus by the presence of accompanying symptoms.
Warning Signs Requiring Immediate Medical Attention
Parents should focus on associated physical symptoms rather than the sound itself. Immediate medical attention is warranted if the baby exhibits any of the following signs:
- The baby cries, flinches, or shows distress when the shoulder is moved or handled.
- Refusal to move the arm on the side of the popping, which doctors refer to as pseudoparalysis.
- Visible swelling, bruising, or warmth around the shoulder or collarbone area, suggesting inflammation or injury.
- A persistent grinding or grating sensation, distinct from a sharp, single click.
- The joint noise is accompanied by a fever, which may suggest a rare joint infection.