THURSDAY, Feb. 26 (HealthDay News) -- More people are lining up for hip and knee replacements, just as the number of surgeons who do them is falling, two new studies reveal.

Both reports were presented Wednesday at the American Academy of Orthopaedic Surgeons annual meeting, in Las Vegas.

"In 2016, nearly 200,000 patients who require hip replacement and 750,000 patients who require knee replacement will not be able to have their surgery performed, because there will not be enough orthopedic surgeons available to do the procedure," said Dr. Thomas K. Fehring, lead researcher of the first study and an orthopedic surgeon with OrthoCarolina in Charlotte, N.C.

For the study, Fehring's team looked at the retirement age of doctors performing hip and knee replacements and the number of new doctors entering the field. Using this data, the researchers calculated the number of doctors who will be available to perform these procedures in 2016.

They found that by 2016, there will be significantly fewer doctors available to replace those who retire. By 2016, 46 percent of patients needing hip replacements will not get them, and 72 percent of those needing knee replacements will have to wait.

"I understood that there were not as many young surgeons going into the arthroplasty field as were retiring from the arthroplasty field, but it shocked me that, if the trends continue, nearly a million patients who need hip and knee replacements in 2016 will not have access to this life-changing procedure," Fehring said.

Low insurance reimbursements for these procedures appear to be keeping new doctors from choosing this specialty, Fehring said. Reimbursement for joint replacement has decreased 60 percent in inflation adjusted dollars since 1990.

"These economic realities are not lost on our residents in training when selecting a career," Fehring said. "Unless things change, this will lead to excessive waiting times for our senior citizens requiring joint replacement. Wait times of one to two years may ensue, which will be unacceptable to the general public," he said.

In the second study, Steven M. Kurtz, vice president of Exponent Inc., an engineering and scientific consulting firm based in Philadelphia, and his colleagues found the dramatic increase in the demand for joint replacements is largely driven by younger patients.