Why Do Shoulders and Knees Pop? Understanding the Causes Behind Joint Noises

Understanding why shoulders and knees pop can help you determine whether it’s just a normal part of joint movement or something that requires further investigation.

1. What Causes Joints to Pop?

Before diving into the specific causes of popping in the shoulders and knees, it’s important to understand the general mechanisms behind joint noises. Here are the primary reasons why joints pop:

• Gas Bubbles: One of the most common reasons for joint popping is the presence of gas bubbles in the synovial fluid, which lubricates the joints. When you move your joints, the pressure within the joint capsule changes, causing these gas bubbles to collapse or burst, resulting in a popping or cracking sound. This is similar to the sound you hear when cracking your knuckles.

• Ligaments and Tendons: Ligaments and tendons are connective tissues that support and stabilize your joints. When you move, these tissues can stretch and snap back into place, sometimes making a popping or snapping sound as they do so. This is particularly common in joints like the knees and shoulders, where multiple tendons and ligaments are involved in complex movements.

• Cartilage Wear and Tear: In some cases, joint popping can be related to the wear and tear of cartilage, the smooth tissue that covers the ends of bones in a joint. As cartilage wears down due to aging or injury, the rougher surfaces of the bones may rub against each other, creating noise during movement. This is more common in joints that have experienced significant stress or degeneration.

2. Why Do Shoulders Pop?

The shoulder is one of the most complex and mobile joints in the body, capable of a wide range of motion. This complexity makes the shoulder more prone to popping and clicking sounds. Here are some common reasons why shoulders pop:

• Labral Tears: The labrum is a ring of cartilage that surrounds the shoulder socket and helps keep the ball of the shoulder joint in place. A tear in the labrum can cause the shoulder to become unstable, leading to a popping or clicking sound during certain movements, such as lifting the arm overhead or rotating the shoulder.

• Rotator Cuff Issues: The rotator cuff is a group of muscles and tendons that stabilize the shoulder joint. Tendinitis, bursitis, or tears in the rotator cuff can cause the tendons to snap or rub against the surrounding structures, producing a popping sound.

• Shoulder Impingement: Shoulder impingement occurs when the tendons of the rotator cuff become pinched between the bones of the shoulder. This can lead to inflammation and irritation, often accompanied by popping or clicking noises during movement.

• Loose Cartilage or Bone Fragments: Injuries or degeneration can cause small pieces of cartilage or bone to break off and float within the joint. These fragments can get caught in the joint during movement, leading to popping sounds.

• Ligament or Tendon Movement: As you move your shoulder, the ligaments and tendons may shift position or snap back into place, creating a popping sound. This is often harmless and may occur during certain arm movements, such as reaching or lifting.

3. Why Do Knees Pop?

Knee popping is also common and can occur for various reasons. The knee joint bears a lot of weight and stress, making it susceptible to a range of issues that can lead to popping or cracking sounds. Common causes of knee popping include:

• Knee Ligament or Tendon Movement: Similar to the shoulder, the ligaments and tendons around the knee can shift position or snap over bony prominences, causing a popping or snapping sound. This is often harmless, especially if it occurs without pain.

• Meniscus Tears: The meniscus is a piece of cartilage that acts as a cushion between the bones in the knee. A tear in the meniscus can cause the knee to pop or click, particularly when twisting or bending the knee. This type of injury is often accompanied by pain, swelling, and limited mobility.

• Patellofemoral Pain Syndrome (Runner’s Knee): This condition occurs when the cartilage under the kneecap (patella) becomes irritated. The misalignment of the patella can cause it to rub against the femur, leading to a popping or grinding sound during knee movement, especially when going up or down stairs.

• Cartilage Wear (Osteoarthritis): As with other joints, the wear and tear of cartilage in the knee can lead to rough surfaces that produce noise during movement. Osteoarthritis is a common cause of this type of popping, particularly in older adults.

• Bubbles in the Synovial Fluid: Just like in the shoulder, gas bubbles in the knee’s synovial fluid can cause popping sounds when they collapse during movement. This is generally harmless and not associated with pain.

4. When Should You Be Concerned?

While most joint popping is harmless, there are situations where it may indicate a more serious issue that requires medical attention. You should consider seeing a healthcare provider if:

• Pain Accompanies the Popping: If the popping sound is accompanied by pain, swelling, or a loss of function, it could be a sign of an injury or underlying condition that needs treatment.
• The Popping is Persistent: Frequent or constant popping in the same joint, especially if it gets worse over time, may warrant an evaluation to rule out any structural damage or degenerative conditions.
• Your Joint Feels Unstable: If your shoulder or knee feels unstable, gives way, or locks up along with popping noises, it could be a sign of a ligament tear or other injury that requires medical intervention.

5. What Can You Do About Joint Popping?

If your shoulder or knee popping is not associated with pain or other symptoms, it’s generally not something to worry about. However, if you’re concerned or experiencing discomfort, here are some steps you can take:

• Strengthening Exercises: Strengthening the muscles around your joints can help stabilize them and reduce the likelihood of popping. Focus on exercises that target the shoulder or knee, such as resistance training or physical therapy.

• Stretching and Mobility Work: Regular stretching and mobility exercises can help maintain flexibility and prevent the tightness that can lead to ligament or tendon snapping. Yoga and dynamic stretching routines are great options.

• Proper Warm-Up: Before engaging in physical activity, ensure you warm up properly to prepare your joints and muscles. This can reduce the chances of sudden popping during exercise.

• Ice and Rest: If you experience popping along with minor pain or swelling, applying ice and resting the joint can help reduce inflammation and prevent further irritation.

• See a Specialist: If the popping is persistent, painful, or causing concern, consult with a healthcare professional, such as a physical therapist, orthopedist, or sports medicine specialist, for a thorough evaluation and personalized treatment plan.

Conclusion

Popping sounds in the shoulders and knees are common and can occur for a variety of reasons, from harmless gas bubbles to more serious conditions like ligament tears or cartilage damage. While most instances of joint popping are benign and not associated with pain, it’s important to be aware of any accompanying symptoms that could indicate an underlying issue. By understanding the potential causes and taking steps to maintain joint health, you can reduce the frequency of these noises and keep your joints functioning smoothly.

At Princeton Sports and Family Medicine, P.C., our doctors specialize in sports medicine services, including exercise counseling and physician services to assess your risk for injury and assist in your performance goals.

Call or click to book a session with our professionals at Princeton Sports and Family Medicine, P.C. In addition to problem-focused visits, we offer sports performance evaluations to stop problems before they start. Plan your visit today!

Author

Peter Wenger, MD Peter C. Wenger, MD, is an orthopedic and non-operative sports injury specialist at Princeton Sports and Family Medicine, P.C., in Lawrenceville, New Jersey. He is board certified in both family medicine and sports medicine. Dr. Wenger brings a unique approach to sports medicine care with his comprehensive understanding of family medicine, sports medicine, and surgery. As a multisport athlete himself, he understands a patient’s desire to safely return to their sport.