District of Columbia Fire Chief Burton W. Johnson, 60, is seeking a $29,000 tax-free disability pension based on a back injury he suffered in a fall in 1943, according to records obtained by The Washington Post.

Johnson is scheduled to appear before the Police and Firemen's Relief and Retirement Board today.

Board decisions on any individual case are entirely secret, and doctors and board members have refused to discuss this case.

According to the records obtained by The Post, however, Johnson is maintaining he was injured in the line of duty when he fell through the roof of one-story home while fighting a fire 35 years ago. He has subsequently aggravated the back injury in a couple of off-duty car accidents and while bending over a filing cabinet at work and now suffers from a "degenerated" disk according to his doctors. They now say he should be retired on disability for a line-of-duty injury.

A specialist contacted by The Post yesterday, Dr. Thomas Powell, an instructor of orthopedic surgery at Johns Hopkins School of Medicine, said that a degenerated disk is a common condition, the result of aging.

"In a 60 year old man, you're surprised if you don't see it," Powell said in response to a reporter's question. Generally, he said, "the existence of a degenerated disk is no more the cause of retirement than gray hair. It's just part of getting old."

The disability pension system for Washington's police and firemen has come under increasing scrutiny recently from Congress and citizens.

The system was brought again into focus last month when Police Chief Maurice J. Cullinane retired on $32,000 tax-free pension citing complications from a 10-year-old knee injury. Subsequently it was learned that 82 percent of the police retirees and 83 percent of the firemen have retired on disability.

Johnson claims his back hurts. His spokesman, Francis X. Flaherty, has said he has seen the chief in such pain "he can hardly stand."

The D.C. Code states that if the board finds a man "permanently disabled" from an injury in the line of duty he is eligible to receive between 66 and 70 percent of his salary. Johnson would receive the maximum because of his 35 years of service. The board also can find that Johnson is disabled, but that his injury did not occur in the line of duty, but was aggravated by his work. In that case he could if he chooses, receive 40 percent of his $41,500 salary tax free.

If the board finds that he is not disabled or that there is no connection between his injury and his work, he can go out on regular retirement, which entitles him to 81 per cent of his salary, subject to taxes.

The Internal Revenue Code permits citizens in other jobs who receive disability pensions a maximum tax-free exemption of only $5,200.

Dave Ryan, president of the local firefighters union, cites statistics showing that the job of a fireman is the most dangerous of all occupations. Because of the hazards, he maintains, it is impossible to be a fireman for any length of time, certainly for 35 years, without being injured in some way.

Police and fire unions have been instrumental over the years in persuading Congress to legislate for Washington firefighters and police a retirement system that is among the most generous in the country.

Johnson worked yesterday and was reported to be "in conference" and unavailable for comment.

According to his medical records he was not treated for his 1943 injury. Flaherty explained recently that in those years superiors looked unfavorably on firefighters who went on sick leave.

He was hospitalized from July 4, 1960, to July 11, 1960, for back strain, and again from June 28, 1965, to July 16, 1965, after he hurt his back lifting an object at home, the records indicate.

In 1965 and 1975 he suffered back injuries from off-duty auto accidents. The first one led to hospitalization and traction and the second to sick leave for two weeks.

When he complained of persistent back pain three years ago, doctors at the police and fire clinic sent Johnson to an outside consultant, a routine procedure, Dr F. Donald Cooney reported that Johnson had "chronic specialists say is a technical term for arthritis.

Cooney most recently examined Johnson last Nov. 3 and concluded that he suffered from a "degenerated lumbar disk superimposed on traumatic arthritic changes in the thoracic and lumbar spines." That means a disk was worn and causing him pain, specialists said.

It could not be determined yesterday why clinic doctors have determined that Johnsons's condition is traceable to an on-duty injury, since the only one that would seem to qualify occurred 35 years ago. The same doctors have ruled out such old injuries as the cause of disabilities inother applicants before the board, according to informed sources.