Introduction

Rheumatoid arthritis (RA) is an autoimmune disease characterised by inflammation, pain, and stiffness within the joints, most commonly the hands and feet.¹ It affected around 18 million people across the world in 2019, and is most common in females and older people.² RA can be very painful and debilitating, and often requires tailored treatment programmes to successfully manage the condition. 

Tenosynovitis is a common symptom of RA and can be indicative of the beginning of the development of RA. However, it can also occur independently of RA. It is defined as an inflammation of the tendon sheath (the layer of protective tissue surrounding tendons). It can occur as a result of infectious diseases, overuse or through autoimmunity. This autoimmune route is where the connection between tenosynovitis and RA comes in. Up to 87% of patients with rheumatoid arthritis show similar clinical presentations to tenosynovitis on MRI images.³

This article aims to provide a background on RA and tenosynovitis. It will investigate how the two conditions are interconnected and how this may help in their diagnosis and treatment.

Pathophysiology

In patients with RA, tenosynovitis develops by the inflammation of the tendon sheath as a result of an autoimmune response. This occurs when the immune system mistakes the healthy cells within this sheath for foreign, unhealthy cells and begins generating an immune response towards them. Some of the immune cells that are responsible include B-cells, T-cells and macrophages.⁴ These cells use a wide range of mechanisms to induce inflammation. For example, B-cells produce antibodies that usually function to fight off infection within the body. In RA, these cells produce dysregulated antibodies such as rheumatoid factors, pro-inflammatory cytokines and anti-citrullinated proteins. This causes an inflammatory response within the joints and, in the case of tenosynovitis, around tendons.⁴

Clinical manifestations 

Generalised symptoms for both RA and tenosynovitis are pain, stiffness, swelling and tenderness around the affected area. Tenosynovitis can be brought about by overuse, injury or infection, as well as from chronic systemic inflammation that occurs in RA. Therefore, it is important for clinicians to understand and be able to determine what the cause of the tenosynovitis might be, in order to treat the condition appropriately. Tenosynovitis caused by infection usually coincides with fever and evidence of injury, whereas symptoms of non-infectious tenosynovitis tend to gradually present themselves over time with no obvious root cause.⁵

This condition is particularly present in the hands, wrists and ankles, and it can even affect nearby nerves, causing loss of feeling and weakness. Improving the diagnostic capabilities for tenosynovitis will coincidentally aid in RA diagnosis, as tenosynovitis has been recognised as an indicator for the beginning of RA development. Diagnosing RA can be quite difficult, as there is no formal diagnostic criterion, and it shares similar symptoms with other diseases such as osteoarthritis, viral arthritis, and metabolic diseases.⁶ More research is warranted for the autoimmune inflammatory diseases in order to prevent long-term complications and improve the quality of life of those affected.

Diagnosis

Clinicians specialising in these types of diseases are called rheumatologists. They often have to do extensive testing, closely monitor patient responses to treatment and have continuous follow-ups to work with the patients to try and manage these debilitating conditions. The following diagnostic tests are commonly used:

Laboratory testing 

The levels of inflammatory cells, which have been linked to RA and related tenosynovitis, can be determined through blood tests. For example, high levels of rheumatoid factors, anti-citrullinated protein antibodies or a high erythrocyte sedimentation rate can all be indicative of high levels of inflammatory markers within the body.⁷ Having these indicators in your blood does not confirm that RA and potential associated tenosynovitis are present, but they can help aid diagnosis when combined with other evidence.

Imaging techniques

• Ultrasound scans 

Ultrasound imaging utilises high-frequency sound waves to create images of internal tissues. It can be used to detect changes within tendon structure and shape to aid in the diagnosis of tenosynovitis. Thicker tendons with less defined outlines can indicate disease.⁸

• Magnetic resonance imaging 

This technique can create detailed images of joints and soft tissues potentially affected by RA and tenosynovitis using radio waves and magnetic fields. It is far more detailed than ultrasound scans, so it can be used when these have not been able to provide sufficient evidence for diagnosis. In one study, MRI images showed tenosynovitis within the wrists of over half of the patients who had suspected RA.⁹

• Computerised tomography

CT scans use X-rays to form cross-sectional images of the body, and show a very clear contrast between bone and soft tissue. It can therefore be used successfully to identify bone abnormalities that may indicate RA. However, it has not been particularly useful in identifying tenosynovitis when compared to MRI.¹⁰ 

Clinical examination

Swelling, redness, and evidence of reduced movement within the joint can be indicative of tenosynovitis.⁵ This is evident when the tendons in the finger seize up and cause the finger joints to lock up, so the finger is stuck in a position that resembles pulling the trigger of a gun, hence the name ‘trigger finger’. Lumps called rheumatoid nodules alongside other clear deformities, often seen in hands, feet, and other joints, are all common signs of RA, aiding overall diagnosis.¹¹

Treatment and management

Treatment options for RA often include incorporating various interventions into a long-term treatment plan. These include drugs,  physical therapy, lifestyle interventions, and in severe cases, surgery may be required to repair the damage done by the long-term inflammation. There has been far less research into treatment options for tenosynovitis. However, due to their association, some options which alleviate RA symptoms have been seen to also help in the context of tenosynovitis. Examples of these are listed below.

• Non-steroidal anti-inflammatory drugs (NSAIDs)

These drugs act by reducing levels of inflammation within the body. As a result, they can lessen the painful symptoms of RA/tenosynovitis. However, they do not target and prevent disease progression, and therefore, the risk of joint damage is not reduced with these drugs.⁶ These drugs can cause side effects such as intestinal issues, as it has been suggested that they may break down the protective linings within the stomach. 

• Disease-modifying anti-rheumatic drugs (DMARDs)

These drugs work by directly blocking the chemicals produced by the dysfunctional immune cells that are active in RA/tenosynovitis, and therefore halting disease progression. They are a consistently successful treatment option. The most commonly used DMARD is called methotrexate, and this is usually the first port of call for most patients. This drug is also used as a chemotherapy for cancers, and can cause several unpleasant side effects.¹² Close monitoring of liver function and blood cell counts is required to ensure this drug is not causing severe damage to the body. In a recent study, 16% of patients had to halt methotrexate treatment due to adverse side effects.¹³

Long-term implications

Tenosynovitis alongside RA can be very painful and debilitating, patients can often feel hopeless due to the lack of a clear diagnosis and treatment pathways. Living with chronic inflammation and resultant pain and immobility can lead to comorbidities such as depression and obesity. It is often so debilitating that people struggle to work, and the economic burden of RA is huge, highlighting the need for more streamlined processes within the healthcare infrastructure.⁶

Long-term complications include irreversible joint and tendon damage and deformity, alongside carpal tunnel syndrome.⁵ When disease progression gets to this stage, surgical intervention is often required, as joint or tendon replacements or whole removal of the inflamed tendon sheath can help alleviate painful symptoms.

Summary

Tenosynovitis in rheumatoid arthritis is gaining traction within the research world, as the coincidences of these two conditions are being recognised and understood more. They are both down to excessive inflammation occurring in and around joints and connective tissues, most commonly affecting the hands, wrists, and feet. These conditions manifest themselves through pain, swelling, and stiffness, inhibiting mobility and decreasing quality of life for those affected. 

Treatment options are multifactorial and successful to an extent. However, due to the lack of understanding of the exact mechanisms of these treatments used to help alleviate symptoms and prevent disease progression, trial and error is often required. This can be tedious and time-consuming for both patients and clinicians, and further research is needed to streamline treatment and increase the incidence of diagnosis early on within the disease's progression. Complex, bespoke treatment plans are essential to improve patient outcomes and help combat the global burden of these conditions.