The authors prepared a Czech version of the ISK (Lequesne) questionnaire. The questionnaire was independently translated by three doctors, followed by discussion of the translation and adoption of the final version. The latter was retranslated into English. This questionnaire was tested as to its reliability, the intra-reliability being 0.98 and evaluation by several examiners 0.97. The validity was tested by means of a double blind controlled trial where a correlation between ISK and pain on the visual analogue scale was demonstrated. The correlation was significant at the onset of the trial (r = 0.38), at the end of the trial (r = 0.73) and correlated with changes in the course of treatment (r = 0.64). In this double blind randomized controlled study the authors compared the symptomatic effect of three different doses of chondroitin sulphate (CS) and placebo (CS 200 mg, CS 800 mg and CS 1200 mg/day). Doses of 800 mg and 1200 mg were more effective than 200 mg and placebo. The differences were apparent from the 42 nd day of treatment onwards. The dose of CS 1200 mg was not more effective than 800 mg. Evidence was provided that the Czech version is sufficiently reliable and valid for use in trials, routine practice and for assessment of patients with knee arthritis.

        Key words: gonarthritis, chondroitin sulphate, questionnaire