Notice incorrect spelling in your original. It's a test for distinguishing between lumbosacral involvement and and damage to the sacroiliac joint. It is explained in the definition below. Your text is referring to degrees of extension of the leg.

It is listed in Dorland's Medical Dictionary; also 768 Internet references to "Goldthwait's sign," all referring to the same test of the spine.

Here is a definition:
Goldthwait's Sign This test is designed to differentiate between sacroiliac and lumbosacral involvement. With the patient supine, the examiner palpates the lumbosacral joint while slowly straight leg raising the limb on the affected side. The test is then repeated on the unaffected side. When pain is brought on before the lumbosacral joint is opened and it's possible to raise the leg on the unaffected side to a greater level than the limb on the affected side without pain, then a lesion of the sacroiliac joint or ligaments is presumed. When no pain is experienced until the lumbosacral movement occurs and pain is felt when either leg is raised to approximately the same height then a lumbosacral lesion is more likely.
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In 1911, the American physician Joel E. Goldthwait (1866–1961) reported on ... or sacro-iliac strain. X-ray examination may be entirely negative, but narrowing of the ...... Osborne, Vol. 2. 63. Jenkins JA (1936) Spondylolisthesis. ...
www.springerlink.com/index/m6r827835jv4q700.pdf

Goldthwait's Sign This test is designed to differentiate between sacroiliac and lumbosacral involvement. With the patient supine, the examiner palpates the ...
Auditory - Brachial Plexus - Cervical - Circulatory
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