# Psoriatic arthritis
**Psoriatic arthritis** (PsA) is a chronic inflammatory joint disease that usually occurs in people with the skin condition psoriasis, causing joint pain, stiffness, and swelling along with inflammation where tendons and ligaments attach to bone.[1](https://medlineplus.gov/ency/article/000413.htm) • [2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis) It occurs in 7% to 42% of people with psoriasis, and in most cases the skin disease appears years before the arthritis.[1](https://medlineplus.gov/ency/article/000413.htm) There is no cure, but medicines can control inflammation and pain, and early treatment is associated with better outcomes and less joint damage.[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis)
| Key fact | Detail |
|---|---|
| Frequency | Occurs in 7% to 42% of people with psoriasis[1](https://medlineplus.gov/ency/article/000413.htm) |
| Typical timing | On average, arthritis develops about 7 to 10 years after skin symptoms begin; usually occurs between ages 30 and 50[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis) • [3](https://medlineplus.gov/genetics/condition/psoriatic-arthritis/) |
| Sex distribution | Most common in adults, affecting men and women equally[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis) |
| Hallmark features | Dactylitis (sausage-like swelling of a whole finger or toe), enthesitis, nail pitting, and possible spine involvement[3](https://medlineplus.gov/genetics/condition/psoriatic-arthritis/) • [2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis) |
| Diagnosis | No specific blood test exists; the CASPAR classification criteria have 91.4% sensitivity and 98.7% specificity[1](https://medlineplus.gov/ency/article/000413.htm) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6135872/) |
| First-line drugs | NSAIDs for pain and swelling; conventional DMARDs include methotrexate, leflunomide, and sulfasalazine[1](https://medlineplus.gov/ency/article/000413.htm) |
| Advanced therapy | Injectable biologics for disease not controlled with DMARDs; oral JAK inhibitors tofacitinib and upadacitinib are also approved[1](https://medlineplus.gov/ency/article/000413.htm) |
| Prognosis | Joint damage occurs within the first several years in many people; early treatment can ease pain and prevent damage[1](https://medlineplus.gov/ency/article/000413.htm) |
## Who gets it and why
Anyone can develop psoriatic arthritis, but it is most common in adults and affects men and women equally.[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis) The large majority of people who get the disease already have psoriasis when they are diagnosed, though a small group have joint pain before any skin rash.[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis) Having severe, widespread psoriasis appears to increase the chance of developing arthritis, and obesity is also associated with a higher risk among people with psoriasis.[1](https://medlineplus.gov/ency/article/000413.htm) • [2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis) Nail psoriasis is linked to psoriatic arthritis.[1](https://medlineplus.gov/ency/article/000413.htm)
The cause is not known. Psoriatic arthritis is an immune-mediated disease, meaning the immune system becomes overactive and creates inflammation; genes, immune system factors, and the environment all appear to play a role.[1](https://medlineplus.gov/ency/article/000413.htm) • [2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis) Many people with the disease have a family history, and researchers have identified some of the genes involved. Stressful events, joint or bone trauma, and infections may trigger onset in some people.[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis)
## Symptoms and clinical features
Symptoms vary greatly from person to person, which can make the disease hard to diagnose.[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis) The arthritis may be mild and involve only a few joints, or it may be severe and affect many joints, including the spine.[1](https://medlineplus.gov/ency/article/000413.htm) The joints at the ends of the fingers or toes may be more affected, and the disease can involve one side of the body or both.[1](https://medlineplus.gov/ency/article/000413.htm) Joint stiffness is often worse in the morning or after resting.[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis)
**Characteristic manifestations** include several features that distinguish the disease from other inflammatory arthritides:
- Dactylitis, painful sausage-like swelling of a whole finger or toe, caused by swelling and redness of the tissues around the joints.[3](https://medlineplus.gov/genetics/condition/psoriatic-arthritis/) • [2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis)
- Tenderness in the entheses, the areas where tendons or ligaments attach to bone; the back of the heel and the sole of the foot are commonly affected spots.[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis) Tendons such as the [Achilles tendon](https://www.edgepedia.org/achilles-tendon), the [plantar fascia](https://www.edgepedia.org/plantar-fascia), and the tendon sheath in the hand may become inflamed.[1](https://medlineplus.gov/ency/article/000413.htm)
- Nail changes such as pitting or crumbling, and nails separating from the nail bed.[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis)
- Spine involvement, with stiffness and pain most often in the lower spine and sacrum.[1](https://medlineplus.gov/ency/article/000413.htm)
- Eye inflammation, especially uveitis, which can cause eye pain, redness, and blurry vision and must be treated promptly to avoid vision loss.[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis)
- Fatigue or lack of energy.[2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis)
Most of the time, people with the disease have the skin and nail changes of psoriasis, and often the skin worsens at the same time as the arthritis.[1](https://medlineplus.gov/ency/article/000413.htm)
## Enthesitis and disease mechanisms
Entheses are the insertion sites of tendons and ligaments on the bone surface, and inflammation of these sites (enthesitis) is a key feature of psoriatic arthritis and spondyloarthritis.[5](https://www.nature.com/articles/nrrheum.2017.188) Mechanistically, enthesitis arises from activation of prostaglandin E2 and the IL-23–IL-17 axis, leading to an influx of innate immune cells into the entheses, followed by tissue responses that produce new bone formation.[5](https://www.nature.com/articles/nrrheum.2017.188) Mechanical stress, genetic susceptibility, and microbial-triggered immune activation combine to activate the specific immune microenvironment of the entheses.[5](https://www.nature.com/articles/nrrheum.2017.188)
Psoriatic arthritis is anatomically more heterogeneous than rheumatoid arthritis: beyond synovitis (inflammation of the joint lining), it often also involves enthesitis, peritendinitis, tenosynovitis, osteitis, and periostitis.[6](https://www.nature.com/articles/s41584-025-01229-6) This heterogeneity has made it difficult to define resolution of inflammation objectively after treatment, with enthesitis posing a particular challenge.[6](https://www.nature.com/articles/s41584-025-01229-6)
## Diagnosis
There is no definitive test for psoriatic arthritis.[7](https://www.niams.nih.gov/health-topics/psoriatic-arthritis/diagnosis-treatment-and-steps-to-take) [Diagnosis](https://www.edgepedia.org/diagnosis) rests on the clinical picture: a doctor asks about symptoms and family history of psoriasis or psoriatic arthritis, examines the joints, skin, and nails, and orders imaging such as x-rays, ultrasound, or MRI, which can reveal changes in joints, entheses, or the spine.[7](https://www.niams.nih.gov/health-topics/psoriatic-arthritis/diagnosis-treatment-and-steps-to-take) Blood tests are used to check for other conditions, such as rheumatoid arthritis, by measuring rheumatoid factor and anti-CCP antibodies; there are no specific blood tests for psoriatic arthritis itself.[7](https://www.niams.nih.gov/health-topics/psoriatic-arthritis/diagnosis-treatment-and-steps-to-take) • [1](https://medlineplus.gov/ency/article/000413.htm) Testing for the gene HLA-B27 may be done, since people with spine involvement are more likely to carry it, though most HLA-B27-positive people do not have psoriatic arthritis.[1](https://medlineplus.gov/ency/article/000413.htm)
For classification in studies, the CASPAR (ClASsification criteria for Psoriatic ARthritis) criteria require established inflammatory articular disease plus at least 3 points from features including current psoriasis (scored 2), a personal or family history of psoriasis, dactylitis, juxtaarticular new bone formation, rheumatoid factor negativity, and nail dystrophy.[8](https://acrjournals.onlinelibrary.wiley.com/doi/10.1002/art.21972) Derived from a prospective study of 588 consecutive PsA patients and 536 controls at 32 centers worldwide, the criteria showed 91.4% sensitivity and 98.7% specificity, and they allow classification of PsA even in patients without current psoriasis.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6135872/)
## Treatment
Treatment depends on the pattern and severity of symptoms, and options have continued to expand.[7](https://www.niams.nih.gov/health-topics/psoriatic-arthritis/diagnosis-treatment-and-steps-to-take) The usual sequence runs from oral anti-inflammatory drugs to disease-modifying drugs to injectable or targeted synthetic agents.
- **NSAIDs** (nonsteroidal anti-inflammatory drugs) reduce pain and swelling of the joints and are suggested first.[1](https://medlineplus.gov/ency/article/000413.htm)
- **Conventional DMARDs** (disease-modifying antirheumatic drugs) are used when arthritis does not improve with NSAIDs; they include methotrexate, leflunomide, and sulfasalazine.[1](https://medlineplus.gov/ency/article/000413.htm)
- **Apremilast**, a phosphodiesterase-4 inhibitor, is another oral medicine used for the disease.[1](https://medlineplus.gov/ency/article/000413.htm)
- **Biologic medicines**, given by injection, are effective for progressive disease not controlled with DMARDs; they block proteins involved in the inflammation process and are often helpful for both the skin and the joint disease.[1](https://medlineplus.gov/ency/article/000413.htm)
- **JAK inhibitors**: two oral JAK inhibitors, tofacitinib and upadacitinib, are approved for psoriatic arthritis.[1](https://medlineplus.gov/ency/article/000413.htm)
- **Steroid injections** into a joint can treat very painful joints when only one or a few are involved; most experts do not recommend oral corticosteroids because they may worsen psoriasis and interfere with other medicines.[1](https://medlineplus.gov/ency/article/000413.htm)
- **Surgery** to repair or replace damaged joints is needed in rare cases.[1](https://medlineplus.gov/ency/article/000413.htm)
Supportive measures include a mix of rest and exercise, physical therapy to increase joint movement, and heat and cold therapy.[1](https://medlineplus.gov/ency/article/000413.htm) People whose disease does not improve with NSAIDs should generally see a rheumatologist along with a dermatologist for the psoriasis.[1](https://medlineplus.gov/ency/article/000413.htm)
**Choosing among targeted therapies.** Because few head-to-head trials exist, network meta-analyses of randomized trials inform comparisons. A 2022 synthesis found that despite similar efficacy for ACR response across drug classes, IL-17A and IL-17RA inhibitors and guselkumab offered preferential efficacy over anti-TNF agents for skin manifestations and for enthesitis and dactylitis, supporting drug selection based on a patient's predominant clinical phenotype.[9](https://rmdopen.bmj.com/content/8/1/e002074) An earlier meta-analysis in biologic-naive patients found infliximab most effective for ACR response, followed by golimumab and etanercept, with few safety differences between treatments.[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC7046955/)
## Prognosis
The disease is sometimes mild and affects only a few joints, but in many people joint damage occurs within the first several years, and very bad arthritis may cause deformities in the hands, feet, and spine.[1](https://medlineplus.gov/ency/article/000413.htm) Early treatment can ease pain and prevent joint damage, even in severe cases, which is why prompt medical attention when joint symptoms arise matters.[1](https://medlineplus.gov/ency/article/000413.htm) • [2](https://www.niams.nih.gov/health-topics/psoriatic-arthritis)
## References
1. [Psoriatic arthritis, MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000413.htm)
2. [Psoriatic Arthritis: Symptoms, Causes, & Risk Factors, NIAMS](https://www.niams.nih.gov/health-topics/psoriatic-arthritis)
3. [Psoriatic arthritis, MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/psoriatic-arthritis/)
4. [Classification and Outcome Measures for Psoriatic Arthritis, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC6135872/)
5. [Enthesitis: from pathophysiology to treatment, Nature Reviews Rheumatology (2017)](https://www.nature.com/articles/nrrheum.2017.188)
6. [Delineating inflammatory from non-inflammatory mechanisms for therapy optimization in psoriatic arthritis, Nature Reviews Rheumatology (2025)](https://www.nature.com/articles/s41584-025-01229-6)
7. [Psoriatic Arthritis: Diagnosis, Treatment, and Steps to Take, NIAMS](https://www.niams.nih.gov/health-topics/psoriatic-arthritis/diagnosis-treatment-and-steps-to-take)
8. [Taylor W et al. Classification criteria for psoriatic arthritis: Development of new criteria from a large international study, Arthritis & Rheumatism (2006)](https://acrjournals.onlinelibrary.wiley.com/doi/10.1002/art.21972)
9. [Targeted systemic therapies for psoriatic arthritis: a systematic review and comparative synthesis, RMD Open (2022)](https://rmdopen.bmj.com/content/8/1/e002074)
10. [Efficacy and safety of biologics in psoriatic arthritis: a systematic literature review and network meta-analysis, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC7046955/)
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*Topic: Encyclopedia › Life and health › Human health and medicine › Diseases and injuries › Skin and musculoskeletal conditions › Musculoskeletal conditions › Arthritis and crystal arthropathy*
*Initially written Sep 17, 2026 · Reviewed: Sep 17, 2026; Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license