Typically affecting flexor tendon function in the hand, tenosynovitis occurs when a tendon and its fluid-filled sheath—called the synovium—become inflamed, often due to infection. Patients with infectious tenosynovitis have a good chance for recovery if they treat the condition promptly and have no comorbidities. However, those with chronic infection or an impaired immune response are at risk for long-term complications. The infectious form of this condition may develop any time after a penetrating injury. Symptoms include pain, redness, and fever, as well as swelling, pain, and tenderness in the affected area. Certain types of infections also may cause dermatitis. Non-infectious tenosynovitis may result from repeated motion of the hand (e.g., with the use of hand tools), injury, or arthritis. In some cases, it appears to run in families, and it affects men more than women. Diagnosis of the condition may involve a physical exam, culture samples, blood work, biopsy, or medical imaging. To effectively treat tenosynovitis, some patients may need to undergo surgery. Alternative treatments include antibiotics administered via IV, elevation, splinting (for compression), icing, administration of anti-inflammatory medications or oral steroids, injections of corticosteroids, and rehab therapy in the form of range of motion exercises and edema control.