The index for hip disease (ISH) was established, validated and appraised as a new assessment test for the trial of new drugs as well as for long-term follow-up of patients, and to help with future indications for surgery. The ISH deals with pain, maximum walking distance, and some activities of daily living. Inter-observer reproducibility is good (mean deviation 0.55 points; p less than 0.05). In a short-term, double-blind crossover trial, the ISH, judged according to its power to distinguish between the active drug period and the placebo period, appears as one of the best assessment tests. In the long term, total hip prosthesis is most often justified when the ISH score reaches 10-12 points. The index of severity for knee disease (ISK) was validated and appraised by the same statistical methods. Its value in non-steroidal anti-inflammatory drug (NSAID) or analgesic trials is lower than the value of the ISH. However, its use is still justified for that purpose, and for long-term follow-up of osteoarthritis of the knee.