The grizzly Catch-22 faced by hundreds of thousands of crippled and mentally disabled people on the Social Security disability rolls is explored in an angry, emotional documentary, with lots of heart-tugging pictures, narrated by Jessica Savitch at 8 p.m. tonight on Channel 26.

The Social Security administration tells people their cases have been reviewed and that even though they have been on disability for years, it has decided that they actually are able to work. Maybe they can't lift heavy loads or stand on their feet for hours at a time, but they can do something, they are told. So their benefits are to be cut off.

But when they go out and actually look for a job--as in the case of Calvin Bickham of Castor, La., highlighted in the "Frontline" documentary "Who Decides Disability?"--the company doctors tell them they're really too disabled for any available jobs.

So they are caught: the pensions on which they've come to depend are gone, unless they get the initial ruling overturned on appeal. But the prospect of any "substantial gainful employment," the mush-mouthed bureaucratic phrase that means a decent job, is just as far away as before.

Although many don't realize it, the massive reviews to see if people on the disability rolls still are too disabled to work have become a major and painful political issue all over the country.

In 1980, Congress mandated that Social Security look at the rolls and throw off anyone who didn't meet the extremely rigorous test of the law--that a person be incapable of any type of work (not merely unable to do what he or she did before getting ill), regardless of whether such a job actually is available and whether the individual would be likely to get it.

Since 1981, 768,000 cases have been reviewed and 355,000 people have been ordered off the rolls. Of those, 88,000 have been restored after appeal.

The review process has brought protests that people are being thrown off. On the program, Sen. John Heinz (R-Pa.) says Social Security has "systematically terminated benfits for individuals who can't possibly work."

The central political question is whether the Reagan administration has sent a strong signal to state and federal examiners, as one state examiner told "Frontline," to "interpret the regulations very strictly" in order to push the greatest possible number off the rolls and thereby save money under President Reagan's federal budget-cutting drive.

The documentary pretty clearly answers this question with a "yes," and not much time or space is given to the Reagan administration for rebuttal. There are a few short excerpts from Social Security deputy commissioner Paul Simmons seeking to explain the administration position and to make the point that the law as written by Congress is extremely rigorous in its test of who shall be eligible. But the PBS documentary makers appear to know where they want to come out and arrive there.

This presentation is one-sided but the magic of the camera does remind you: the disabled are there.