Side comparison for shoulder pain
Changes in the rotator cuff increase with age and often exist without any complaints: partial ruptures of the supraspinatus tendon after fifty years are found in a significant proportion of people who have never complained about the shoulder. Therefore, the finding in itself does not explain the pain. Examination of a healthy shoulder helps to understand what is the background age norm for a particular person, and what is a recent and clinically significant change.
Bilateral examination is necessary for systemic diseases: rheumatoid arthritis with symmetrical lesions, polymyalgia rheumatica, which is characterized by bilateral subacromial bursitis and biceps tendinitis, gout and calcific tendinitis, often affecting both shoulders sequentially.
A separate group includes people with professional or sports loads on the shoulder girdle: swimmers, volleyball players, painters who work with their arms raised. In them, overload changes develop on both sides, but appear first on the dominant hand. Examination of the second shoulder allows you to identify the process before pain appears and adjust the load in time.
What can be seen on an ultrasound of the joint
Ultrasound, better than any other method, shows the soft tissues surrounding the joint: tendons and their sheaths, ligaments, muscles, synovium, joint capsules and peripheral nerves. It reliably detects free fluid in the joint cavity and bursae, tendon ruptures and tears, cysts, bursitis and tendinitis.
There are also fundamental limitations. Ultrasound does not pass through the bone, so the internal structures - menisci along the entire length, cruciate ligaments, articular cartilage deep in the joint, bone marrow - remain inaccessible. They use magnetic resonance imaging, and X-rays are used to evaluate the bone itself.
The main advantage is exploration in motion
Unlike MRI, which takes a picture of a motionless joint, ultrasound allows you to look at the joint in dynamics. The doctor asks you to bend, straighten or rotate the limb straight during the scan and sees how the tendons and ligaments behave under load.
Many conditions manifest themselves only during movement: tendon subluxation from the groove, impingement, trigger finger, ligament instability. At rest, the picture looks normal, and without functional tests the diagnosis cannot be made.
When to start with ultrasound
Ultrasound is reasonable as the first method for pain and swelling of the joint without injury, for suspected bursitis, tendinitis and cysts, for monitoring the treatment of inflammatory diseases and, if necessary, to induce a puncture or blockade.
If there was a serious injury with a suspected fracture, you need to start with an x-ray. If a torn meniscus or cruciate ligament is suspected, MRI remains the method of choice.