Osteoarthritis vs PsA: Decoding the Differences

Diagnosing psoriatic arthritis (PsA) can be a real challenge, especially since there are several arthritic conditions that can present similarly to one another. PsA is often misdiagnosed for rheumatoid arthritis, gout, or osteoarthritis, just to name a few. PsA is usually distinguished by the types of joints affected or the presence of accompanying psoriasis. But even so, diagnosis can be a challenge, and take some time. Osteoarthritis is the most common chronic joint condition and affects nearly 30 million Americans. Some estimates even report that as many as 70% of individuals between the age of 55 and 78 are affected with osteoarthritis. Despite its commonality, it is still challenging to separate it from other arthritic conditions, including PsA. However, there are some common differences between the two you can look out for.

Underlying cause and type of pain

While PsA presents with joint stiffness and swelling due to an overactive immune response, osteoarthritis (OA) usually has minimal swelling, and is the result of wear-and-tear to joints. This is why OA affects primarily major or weight-bearing joints, such as the hips, knees, spine, or neck, and typically shows up later in life. PsA can arise across a variety of ages, and often affects the smaller joints of the fingers and toes first (the reason for their “sausage” appearance). The wear-and-tear of OA is a result of cartilage breaking down. Cartilage normally keeps joints smooth and allows them to function without friction, and without it, can lead to clicking or brittle joints.

Additionally, pain and stiffness in PsA is also typically cyclic, with periods of flare-ups and remission, whereas, OA is a degenerative condition that is constantly getting worse, despite attempts at movement. Finally, the risk factors that lead to the development of each condition are also varied. Obesity, advanced age, previous joint injuries or deformities, repetitive motions, and genetics can all play a role in developing OA, whereas PsA’s causes are typically genetics, previous trauma (such as viral or bacterial infections), medications, and stress.

Diagnosis and treatment

OA and PsA are also diagnosed and treated very differently. Diagnosis for PsA often follows the presentation of psoriasis (which could be hiding in hard to notice locations), and diagnostic tests that rule out other conditions (such as the lack of RF-factor in blood tests for rheumatoid arthritis). OA, on the other hand, is a little more definitive in diagnosis. Joint fluid is directly obtained and tested from an affected joint, and often presents with crystals indicative of degeneration. Additionally, X-rays and MRIs, while expensive, have the ability to point pretty definitively towards OA and cartilage destruction, more than typically ambiguous scans of joints with PsA.

Due to their different causes, different treatments are warranted. Since inflammation is not the root cause of OA, typical medications used to treat it do not have anti-inflammatory properties. Many OA medications are strictly pain-focused, while PsA meds are aimed at reducing inflammation and keeping pain at bay. Both conditions have the ability to respond to injected steroids, however, OA may also respond to lifestyle changes, such as dieting to lose weight, in order to relieve stress on joints. In severe cases of both OA and PsA, surgery could be warranted to replace entire joints.

Overall, both conditions can present very similarly, and cause confusion for both individuals with the condition, and the healthcare providers trying to diagnose and treat them. The most important thing is to remain educated and aware of your symptoms, in order to best help your healthcare team get to the root of your struggles!

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