Just after being confirmed as one of this year's contestants, the actor revealed that he has been living with the autoimmune condition.
Now in an Instagram post featuring a topless mirror selfie he has shared how the condition is impacting his life.
"A very rare sight … me with my top off," he wrote in the accompanying caption. "But I need to get comfortable feeling uncomfortable! Am not in the best shape of my life but,I could be worse."
The Strictly star went on to say how "tough" this year has been for him, but he's trying to stay "focused".
"I’m still struggling and the pain is still there but I’m putting on a brave face I’ve got to stay strong!!" he added of his condition.
"Swimming helps me so much with my arthritis, i mean as much as it kills me getting my top off and going for a swim, I know it’s helping me and I know it’s also helping me deal with the issues I’ve got with me and my body. Which is a good thing!"
Last month the star marked his 35th birthday on Instagram with a post confirming this recent diagnosis.
"I've been in a lot of pain since January, it started with my knees and then travelled to my wrists, fingers and now ankles and toes," he wrote alongside a family snapshot with his wife Caroline Daly and the couple's two children.
"I never knew what was happening and finally after several blood tests and back and forth to doctors and hospitals, I've been diagnosed with rheumatoid Arthritis! I thought that was something people, later on in their life get... but that's not the case, clearly!"
Thomas admitted that while it has been "a tough old year" he believes he is on the "right plan now" and is "finally getting it under control".
Despite the health update the actor admitted Strictly is "going to be tough" but he’s "up for the challenge" and still "can’t wait to get on the dance floor".
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What is rheumatoid arthritis?
The NHS describes rheumatoid arthritis as a "long-term condition that causes pain, swelling and stiffness in the joints" with the main areas being affected the hands, feet and wrists.
Those living with the condition may experience periods where symptoms become worse, known as flare-ups or flares.
Rheumatoid arthritis affects around 400,000 people in the UK. While it can impact adults at any age, the condition most commonly starts between the ages of 40 and 50. Interestingly about three times as many women as men are affected.
Rheumatoid arthritis symptoms
Symptoms affecting the joints
Pain, which is usually throbbing and aching.
Stiffness - for example if your hands are impacted you may not be able to fully bend your fingers or form a fist. Like joint pain, stiffness is typically worse in the morning.
Swelling, redness and feeling warm - When the lining of joints affected by rheumatoid arthritis becomes inflamed, it can cause the joints to swell, and become hot and sore.
Nodules - In some people hard swellings, known as rheumatoid nodules can develop under the skin around affected joints.
As well as problems affecting the joints, some people with rheumatoid arthritis have more general symptoms, such as:
Tiredness and a lack of energy
Dry eyes if the eyes are affected
Chest pain – if the heart or lungs are affected
Rheumatoid arthritis risk factors
As an autoimmune condition rheumatoid arthritis is caused by the immune system attacking healthy body tissue.
While it is not yet known what triggers this, experts believe there are a number of factors that may increase your risk of developing rheumatoid arthritis, including:
Genes – there is some evidence that rheumatoid arthritis can run in families, although the risk of inheriting it is thought to be low.
Hormones – rheumatoid arthritis is more common in women than men, which may be because of the effects of the hormone oestrogen. However, as the NHS points out this link has not been proven.
Smoking – some evidence suggests that people who smoke have an increased risk of developing rheumatoid arthritis
Rheumatoid arthritis treatment
While there is no cure, early diagnosis and treatment can help prevent "flare-ups" from being a common occurrence.
However, depending on the severity of the pain, stiffness, and swelling, sufferers might find overcoming everyday tasks more of a challenge.
The main treatment options include:
medication that is taken in the long-term to relieve symptoms and slow the progress of the condition
supportive treatments, such as physiotherapy and occupational therapy, to help keep you mobile and find ways around any problems you have with daily activities
surgery to correct any joint problems that develop