Periarthritis, also known as frozen shoulder or adhesive capsulitis, is a painful shoulder condition that gradually restricts movement and stiffens the joint, often taking months or even years to fully resolve.
Periarthritis is a term that has been used historically to describe a painful shoulder syndrome distinct from typical arthritis. The condition was first described in 1870 by a physician named Duplay, who called it “scapulohumeral periarthritis” to emphasize that the problem affected the tissues around the joint rather than the joint itself. Today, this condition is more commonly known as frozen shoulder or adhesive capsulitis, though the term periarthritis is still used in some medical contexts.[2][3]
The condition earned the name “frozen shoulder” because the shoulder becomes increasingly stiff and difficult to move, as if it were frozen in place. What makes this condition particularly challenging is that it develops slowly, often without an obvious cause, and can significantly limit a person’s ability to perform everyday activities like dressing, reaching overhead, or even sleeping comfortably.[1]
How Common Is Periarthritis?
Periarthritis affects a notable portion of the population, with studies suggesting that between 2% and 5% of people will experience this condition at some point in their lives. The condition shows a clear pattern in who it affects most commonly.[9]
Women are more likely to develop periarthritis than men. The condition most frequently appears in people between the ages of 40 and 60, though it can occur at any age. This age-related pattern suggests that changes in the body’s tissues over time may play a role in the development of the condition.[1][4]
While the shoulder is by far the most common location for periarthritis, the condition can occasionally affect other joints in the body, including the hip, knee, ankle, foot, elbow, wrist, and fingers. However, these other locations are much less frequently involved.[5]
Interestingly, acute calcific periarthritis, a specific form of the condition involving calcium deposits, affects both males and females across a broad age range, with an average age of 45 years. Some researchers have noted that when this form affects the hands and feet, it appears more commonly in women who are approaching or going through menopause.[5]
What Causes Periarthritis?
The exact cause of periarthritis remains somewhat mysterious, even to medical experts. However, researchers have identified several mechanisms and situations that can trigger the condition.[1]
Periarthritis can be classified into two main types based on its origin. Primary or idiopathic periarthritis occurs spontaneously without any clear trigger or preceding event. This is the most puzzling form because there is no obvious reason why the shoulder begins to stiffen and hurt. Secondary periarthritis develops after a specific event, such as shoulder surgery, an injury to the shoulder area, or another illness that requires the shoulder to remain immobile for an extended period.[2]
The disease process involves an inflammatory response in the tissues surrounding the shoulder joint. The shoulder capsule, which is the strong connective tissue that surrounds and protects the shoulder joint, becomes thick, stiff, and inflamed. Over time, thick bands of tissue called adhesions form within the joint capsule. These adhesions act like internal scar tissue, restricting the normal smooth gliding motion of the shoulder.[1][4]
In the normal shoulder, a lubricating fluid called synovial fluid helps the joint move smoothly. In periarthritis, the amount of this fluid decreases, further contributing to stiffness and difficulty moving the shoulder. The inflammation also causes pain, which leads people to move their shoulder less, creating a vicious cycle where lack of movement causes more stiffness, which causes more pain.[4][12]
In some cases of periarthritis, calcium crystals build up around the joint. This form, called acute calcific periarthritis, creates additional inflammation and pain as the body reacts to these deposits. A history of trauma is reported in about one-third of patients with acute calcific periarthritis. Repetitive small injuries from manual work or footwear issues have also been suggested as possible triggers.[5][7]
Who Is at Risk for Developing Periarthritis?
Several factors increase the likelihood that someone will develop periarthritis. Understanding these risk factors can help people and their doctors recognize the condition early.[4][8]
Diabetes is one of the strongest risk factors for periarthritis. Between 10% and 20% of people with diabetes will develop frozen shoulder at some point. The reasons for this connection are not entirely clear, but it appears that high blood sugar levels may affect the connective tissues in the shoulder, making them more prone to inflammation and stiffness.[8][10]
People with thyroid disorders, both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid), face an increased risk of developing periarthritis. The thyroid gland plays a crucial role in regulating metabolism and tissue health throughout the body, and imbalances can affect the shoulder tissues.[4][8]
Cardiovascular disease and heart conditions have also been linked to an increased risk of periarthritis, though the exact mechanism is not well understood. Similarly, people with Parkinson’s disease face a higher likelihood of developing the condition.[8]
Once someone has had periarthritis in one shoulder, there is a possibility it could develop in the other shoulder, usually within five years. However, it is uncommon for the condition to return to the same shoulder that was previously affected.[1]
What Symptoms Does Periarthritis Cause?
The symptoms of periarthritis develop gradually and follow a characteristic pattern that has been divided into three distinct stages. Understanding these stages helps patients and doctors know what to expect as the condition progresses and eventually resolves.[1][4]
The first stage is called the “freezing” stage. During this phase, which typically lasts from six weeks to nine months, pain slowly increases and the shoulder’s ability to move becomes progressively limited. The pain is often described as a deep ache located in the shoulder joint. Any movement of the shoulder causes discomfort, and many people find that the pain worsens at night, making it difficult to sleep, especially when lying on the affected side. This nighttime pain disruption can be particularly distressing and exhausting.[1][4]
The second stage is known as the “frozen” stage. Lasting from four to twelve months, this phase is characterized by a gradual decrease in pain intensity, but the stiffness remains severe or even worsens. During this time, the shoulder feels locked in place, making everyday activities extremely challenging. Simple tasks like reaching into a back pocket, fastening a bra, combing hair, or reaching for items on high shelves become difficult or impossible. The combination of limited movement in all directions and persistent stiffness defines this stage.[1][4]
The third and final stage is the “thawing” or recovery stage. During this period, which can last anywhere from five months to two years, the shoulder gradually begins to loosen. Range of motion slowly improves, and the ability to perform daily activities returns. However, the recovery can be frustratingly slow, and complete return to normal function may take up to three years in total from the onset of symptoms.[1][4]
In acute calcific periarthritis, which involves calcium deposits, symptoms develop more suddenly. Patients experience a rapid onset of severe pain, localized swelling, redness, tenderness, and restricted range of motion around the affected joint. These symptoms typically reduce in severity within four to seven days and self-resolve completely within three to four weeks, which is much faster than typical frozen shoulder.[5]
Throughout all stages of periarthritis, patients may notice grinding, clicking, popping, or cracking sounds in the shoulder joint. These noises occur because the smooth cartilage surfaces have been affected, and the joint no longer moves as smoothly as it should. These sounds may or may not be accompanied by pain.[8]
How Can Periarthritis Be Prevented?
While it is not always possible to prevent periarthritis, especially when it occurs spontaneously, there are several strategies that can reduce the risk of developing the condition or lessen its severity.[10]
The most important preventive measure is avoiding prolonged immobilization of the shoulder. After an injury or surgery, it is crucial to begin moving the shoulder as soon as it is safely possible. Healthcare providers often recommend gentle range-of-motion exercises early in the recovery process to prevent the shoulder capsule from becoming stiff. Even small, controlled movements can help maintain joint flexibility and prevent the development of adhesions.[4]
For people with diabetes, maintaining good blood sugar control appears to be an important preventive measure. Keeping blood glucose levels within the normal range may decrease the chances of developing periarthritis. Regular monitoring and proper diabetes management through diet, exercise, and medication when necessary can help protect the shoulder tissues.[10]
Maintaining a healthy weight can reduce strain on joints throughout the body, including the shoulders. Excess weight can put additional stress on joints and may contribute to inflammation. Regular exercise helps maintain flexibility and strength in the shoulder joint, which can provide some protection against stiffness.[10]
People who work in jobs requiring repetitive shoulder motions or those who participate in sports with high shoulder demands should be mindful of avoiding overuse injuries. Taking breaks, using proper technique, and strengthening the muscles around the shoulder can help prevent injuries that might lead to secondary periarthritis.[5]
Early mobilization after shoulder injuries or surgeries is particularly important. If you have experienced a shoulder injury or undergone shoulder surgery, working with a physical therapist to safely restore movement as soon as appropriate can be crucial in preventing frozen shoulder from developing.[4]
What Happens in the Body During Periarthritis?
Understanding the physical and biochemical changes that occur in periarthritis helps explain why the condition causes such significant pain and stiffness. The disease process involves complex interactions between inflammation, tissue thickening, and scar formation.[2]
The shoulder joint is a ball-and-socket arrangement where the round head of the upper arm bone (the humerus) fits into a shallow socket (the glenoid cavity) on the shoulder blade (the scapula). This joint is surrounded by a flexible capsule made of strong connective tissue that normally allows a wide range of movement. The capsule is filled with synovial fluid, which acts as a lubricant to help the joint move smoothly.[4][12]
In periarthritis, the shoulder capsule undergoes significant changes. The tissue becomes inflamed, which means it becomes swollen, red, and painful due to increased blood flow and immune system activity in the area. This inflammation is associated with higher numbers of immune cells, including fibroblasts (cells that produce connective tissue), mast cells, macrophages, and T cells. These cells release various inflammatory substances, including growth factors and chemical messengers called cytokines and interleukins, which promote tissue scarring and stiffness.[9]
As the inflammation continues, the capsule becomes thicker and tighter. The normally flexible tissue loses its ability to stretch, which restricts shoulder movement. Microscopic examination of affected tissue shows a higher density of collagen fibers arranged in a disorganized pattern, unlike the orderly arrangement seen in healthy shoulder capsules.[2]
Adhesions, which are thick bands of scar tissue, develop within the joint space and between the capsule and the bone. These adhesions act like internal glue, sticking surfaces together that should normally glide smoothly past one another. The development of adhesions is a key factor in the loss of shoulder mobility.[4][12]
The amount of synovial fluid in the joint decreases during periarthritis. With less lubrication, the joint surfaces cannot move as freely, contributing to stiffness and the grinding sensations that some patients experience. The reduction in joint space also means there is less room for the humeral head to move within the socket.[4]
During the examination of frozen shoulders through arthroscopy (a procedure using a small camera to look inside the joint), doctors observe that the capsule appears congested and inflamed, particularly around an area called the rotator interval and certain ligaments. The tissue has a thickened, angry appearance that reflects the ongoing inflammatory process.[9]
In acute calcific periarthritis, calcium crystals accumulate in the soft tissues around the joint. These deposits are made of calcium phosphate and can range in size and location. When these crystals trigger an immune response, they cause sudden, intense inflammation. The body recognizes these deposits as foreign material and mounts an inflammatory response to try to clear them, which causes the acute pain and swelling characteristic of this form of the condition.[5][7]
The entire pathological process of periarthritis represents a cycle where inflammation leads to stiffness, stiffness leads to less movement, and less movement allows more adhesions and scar tissue to form. Breaking this cycle requires interventions that address both the inflammation and the mechanical restriction of movement.[12]
