January 19 (HealthDay News) -- People with severe osteoarthritis tend to be happier with their care and treatment if they see eye-to-eye with their health-care providers on the issue of total knee replacement, a new study finds.

However, about 20 percent of patients don't agree with providers when it comes to this common treatment. Osteoarthritis affects more than 20 million Americans, experts say.

The study, published in the January issue of Arthritis & Rheumatism (Arthritis Care & Research), found agreements between most providers and patients about the importance and potential benefits of the joint replacement surgery, but patients generally had greater concerns about the severity of their condition and possible complications.

"Discrepancies in provider-patient beliefs about the risks, benefits and need for TKR [total knee replacement] are not only a barrier to informed decision-making, but such differences also can affect post-consultation outcomes," study author Richard L. Street Jr., of Texas A&M University, said in a news release from the journal.

The researchers questioned 27 health-care providers and 74 patients with severe osteoarthritis about their views on the need for, risks of, and benefits of the surgery.

The findings indicated that patients who were more in agreement with their providers about the pros and cons of total knee replacement ended up happier with the care they received. They were also more likely to follow the provider's recommendations on treatment.

The authors suggest that the two parties in the study may have discussed the procedure at length without fully talking about why it was even necessary.

"More research is needed on effective information-giving, so that all the requirements of informed decision-making are met," the researchers said.

SOURCE: Wiley-Blackwell, news release, Jan. 7, 2009