Seronegative spondyloarthropathies are a family of joint disorders that classically include ankylosing spondylitis (AS), psoriatic arthritis (PsA), inflammatory bowel disease (IBD) associated arthritis, reactive arthritis (formerly Reiter syndrome; ReA), and undifferentiated SpA. Enthesitis, or inflammation of the sites where the tendons or ligaments insert into the bone, is a key pathological finding in SpA . It is considered the hallmark and characteristic feature of spondyloarthritis (SpA). Entheses could be classified as fibrous entheses and fibrocartilaginous entheses. Regional structural damage, such as tendon injuries and bone erosions, are frequently caused by persistent enthesitis. The healing process that follows may result in the emergence of enthesophytes and, eventually, functional impairment of related anatomic structures. Imaging modalities for evaluating entheseal lesions include conventional radiology, bone scintigraphy, magnetic resonance imaging (MRI) and power Doppler (PD) ultrasound (US). US has its own unique advantage in the diagnosis of enthesitis in AS; it uses a high-frequency or ultra-high-frequency probe that effectively visualizes the internal structure of the tendon and is recognized as the gold standard for tendon involvement.

It is superior to clinical examination in the detection of peripheral enthesitis.

Manifestations of tendon enthesitis in SpA on US include a thickened tendon, hypoechoicity, local calcification and bony erosion. Abnormal blood flow in tendon entheseal sites can be detected by Power Doppler US. Fibromyalgia (FM) is a syndrome characterized by chronic musculoskeletal pain. The main symptoms of which are muscle stiffness, joint stiffness, insomnia, fatigue, mood disorders, cognitive dysfunction, anxiety, depression, general sensitivity and the inability to carry out normal daily activities [8, 9]. It can also be associated with specific diseases, such as infections, diabetes, rheumatic diseases and psychiatric or neurological disorders. Smythe and Moldofsky later developed the name "fibromyalgia" after identifying "pain points," which are areas of severe tenderness. These points are defined as areas of hyperalgesia/allodynia when a pressure of about 4 kg causes pain.

Inclusion Criteria:

• Patients fulfill the Assessment in Spondyloarthrits International Society (ASAS) classification criteria for Axial Spondyloarthritis.
• Age above 18 years old.
• Patient cooperative and can answer questions.
• Patients who are able and willing to give written informed consent.

Exclusion Criteria:

• Other rheumatologic or collagen diseases.
• Age below 18 years and above 60 years.
• Uncooperative patients.
• Patient not able and willing to give written informed consent.

Inclusion Criteria:

• Patients fulfill the Assessment in Spondyloarthrits International Society (ASAS) classification criteria for Axial Spondyloarthritis.
• Age above 18 years old.
• Patient cooperative and can answer questions.
• Patients who are able and willing to give written informed consent.