The general objective of the OPTIMA study is to assess the time course and interrelationship of imaging (ultrasound and magnetic resonance imaging), clinical, laboratory, and Patient Reported Outcome variables in patients with active Psoriatic Arthritis (any subset) and Rheumatoid Arthritis starting therapy with a Jak-Inhibitor (Upadacitinib), during the first 6 months of follow-up.

Participants will be evaluated at the start of therapy with upadacitinib and during the follow-up visits at 2 weeks, 1, 3, and 6 months post-treatment initiation. At each visit (with the exception of the 2-weeks visit), data relating to the clinical evaluation, laboratory tests, and ultrasound of the affected joints will be collected according to standard clinical practice; questionnaires on disease activity will also be completed. In the case of axial involvement, a magnetic resonance imaging will be performed at baseline and after 6 months of therapy, only if required by the standard of care.

This is a multicentric prospective observational study in which consecutive patients diagnosed with Psoriatic Arthritis (any subset) and Rheumatoid Arthritis, that according to clinicians' evaluation should be treated with Upadacitinib therapy, will be recruited from the outpatient clinic of the Rheumatology Department of the centers included in the study.

The investigators will enroll consecutive patients with Psoriatic Arthritis and Rheumatoid Arthritis with active disease and fulfilling the inclusion and exclusion criteria, from the outpatient clinic of the Rheumatology Units of the participating centers. Written informed consent will be obtained prior to the beginning of the study. All patients, in line with clinical routine practice, will undergo a standard clinical, laboratory, and imaging assessment in order to define the disease activity according to standardized disease activity indexes, at baseline and during the first 3 follow-up visits. For patients starting new treatments for Psoriatic Arthritis and Rheumatoid Arthritis, the follow-up visits are generally scheduled after 1 month (± 1 week), 3 months (± 2 weeks), and 6 months (± 4 weeks) post-treatment initiation, in accordance with international guidelines and local protocols. In case of suspicion of axial involvement, an MRI of the sacroiliac joints will be performed at baseline and, in case of positivity, will be repeated after 6 months (±1 month) in order to assess disease activity at the spine and the treatment efficacy. Regarding the Patient Reported Outcome, the investigators will assess these during the scheduled visits, and two weeks after the initiation of treatment to evaluate earlier pain and functional improvement. The Patient Reported Outcome assessment at two weeks will be administered in a paper form to participants during the baseline visit, and subsequently participants will return these during the first follow-up visit. The data for the study will be retrieved from the medical records of participants and recorded into an appositely created electronic case report form.

The inclusion criteria for Psoriatic Arthritis patients are:

1. Patients diagnosed with peripheral Psoriatic Arthritis according to the CASPAR criteria or with axial Psoriatic Arthritis according to ASAS criteria and with at least one of the following:

   1. With active peripheral Psoriatic Arthritis regarding ongoing therapy in one of the following sites: MCP joints 1-5, proximal interphalangeal (PIP) joints of hands 1-5, distal interphalangeal (DIP) joints of hands 2-5, wrists, elbows, knees and ankles/heels and feet, according to any of the following criteria:

      I) DAPSA ≥ 15 and joint inflammation according to the Global OMERACT-EULAR US scoring for synovitis and power Doppler (GLOESS) with a grade at patient level >3,2

      II) With a clinical enthesitis and an active enthesitis (positive power Doppler of any grade), in the clinical symptomatic site, according to the OMERACT US definitions

      III) With active dactylitis (clinical diagnosis made by the physician at the time of baseline visit) and a positive US dactylitis according to the DACTylitis glObal Sonographic (DACTOS) score >3

      IV) DAPSA ≥ 15 and tenosynovitis according to the OMERACT US scoring system for tenosynovitis with a grade >1

   2. With active axial PsA regarding ongoing therapy (ASDAS ≥ 2.1) and active sacroiliitis according to the ASAS MRI definitions

2. Who are eligible according to the current guidelines/regulations to start treatment with UPA and present a favorable risk/benefit profile according to the clinician's opinion for such treatment.

3. Aged older than 18 years.

4. Able to provide informed consent, according to requirements of local IRB/ethics committee.

The inclusion criteria for Rheumatoid Arthritis patients are:

1. Patients diagnosed with RA according to the ACR/EULAR 2010 classification criteria

2. With active Rheumatoid Arthritis according to the following criteria: DAS28-PCR >3.2, and the presence of at least one US finding of the following:

   1. Joint inflammation at hands and wrists according to the Global OMERACT-EULAR (GLOESS) US scoring for synovitis and power Doppler with a grade at patient level >2
   2. One tenosynovitis at hands or wrists, according to the OMERACT US scoring system for tenosynovitis with a grade >1

3. Who are eligible according to the current guidelines/regulations to start treatment with Upadacitinib and present a favourable risk/benefit profile according to the clinician's opinion for such treatment.

4. Aged older than 18 years.

5. Able to provide informed consent, according to requirements of local IRB/ethics committee.

Exclusion Criteria:

1. Patients with any contraindication to Upadacitinib:

   1. women who are pregnant or breastfeeding
   2. active infection
   3. evidence of tuberculosis infection
   4. known infection with human immunodeficiency virus or hepatitis B or C
   5. patients who have current malignancy or history of malignancy in the last 5 years
   6. high cardiovascular risk
   7. high risk of venous thromboembolism
   8. patients with severe hepatic impairment

2. Patients with associated fibromyalgia syndrome according to the 2016 ACR diagnostic criteria

3. Unable to provide informed consent, according to requirements of local IRB/ethics committee.

Patients with active Psoriatic Arthritis and patients with active Rheumatoid Arthritis who will start therapy with upadacitinib