Optimization of analgesics allows patients with knee osteoarthritis and severe pain to participate in exercise therapy. (April 2015) - van Tunen, J.A.; van der Leeden, M.; Bos, W.; Cheung, J.; Gerritsen, M.; Peter, W.F.; Roorda, L.D.; Tijhuis, G.; Voorneman, R.E.; Lems, W.F.; Dekker, J.