Enthesitis is observed in up to 70% of patients with reactive arthritis, and most often manifests as tenderness and sometimes pain, with or without swelling at the entheses. The most characteristic and clinically helpful site of involvement is at the insertion of the posterior and inferior surfaces of the calcaneum (Achilles tendon and plantar fascia insertions, respectively), which can result in painful heels and difficulty on walking. Other common sites include spinal processes, ischium, iliac crest, greater femoral trochanter, tibial tubercle, and the digits (dactylitis). There can also be associated tendinitis or tenosynovitis in Enthesitis.

Enthesitis is an inflammation of the entheses . It is also called enthesopathy, or any pathologic condition involving the entheses. Pain at these points of connection is known as enthesopathy, and inflammation at these sites is known as enthesitis. Metaplasia of fibroblasts at this attachment site results in the formation of fibrocartilage. One of the primary entheses involved in inflammatory autoimmune disease is at the heel. Sometimes other family members may have the same condition or an associated condition, for example, Ankylosing Spondylitis. The regions of tendons and ligaments that make up the entheses are dynamic structures with a high capacity for tissue turnover in order to respond continually to changing mechanical factors These children are at risk of the eye condition acute uveitis but this eye condition is quite different to the one that children who have pauciarticular arthritis may develop The high rate of tissue attrition at the enthesis may partly explain why this is a common target for many diseases of the skeletal system. Heel swelling and inflammation are therefore used to help diagnose certain inflammatory autoimmune diseases, including ankylosing spondylitis.

Symptoms of Enthesitis
-- Inflammation of the tendon and bone may cause shoulder pain and limited mobility of the affected shoulder(s).
-- It is common for patients with these diseases to complain of general fatigue, stiffness, joint pain or swelling, especially in the early morning hours.
-- As with any chronic inflammatory disease, patients with AS may have fatigue and malaise. Disturbed sleep, caused by back or joint pain at night, may contribute to fatigue. Low-grade fevers and weight loss can also occur in some patients.
-- Inflammation of the prostate gland (prostatitis)
-- Joint stiffness
-- Fever and general feeling of being unwell

Treatnent of Enthesitis :
-- NSAID therapy needs to be individualized
-- Medications such as NSAIDs (non-steroid anti-inflammatory drugs) and DMARDs (disease modifying anti rheumatoid drugs) to reduce inflammation in the affected joints and avoid long-term damage to those joints.
-- Intra-articular corticosteroid injections into acutely inflamed joints do not have as dramatic or as sustained a response as in rheumatoid arthritis
-- Your doctor may prescribe an antibiotic to eliminate the bacterial infection that triggered your reactive arthritis if it's still detectable in your body.
-- It has been shown that physical therapy (PT) can significantly improve symptoms in patients with AS, helping with range of motion and control of pain.
-- TNF is a cell protein (cytokine) that acts as an inflammatory agent in rheumatoid arthritis.
-- Pain relieving drugs (such as codeine and other narcotics) and sedatives (sleeping pills) should also be used cautiously, if at all, since these also increase the risk of falling