The injection frequently includes components of normal healthy joint fluid known to be reduced in arthritis. While the exact mechanism of benefit is not known, many patients, especially with early arthritis, can benefit from these injections for a variable period of time. Acetaminophen (Tylenol) containing products can be very useful analgesics in arthritis. Given its low cost and good side effect profile, it is a good first-line drug for treating arthritis. It should be avoided in some patients with a history of liver disease and care should be taken not to exceed the total  daily dose of 4gm per day.