[Psychological factors in the context of perioperative knee and joint pain: the role of treatment expectations in pain evolvement].

Chronic knee and joint pain, like all chronic pain, is a complex multidimensional event that involves somatic, psychological and social factors. Patients with knee and other joint pain experience limited mobility in their daily lives, in their professional and personal activities, and in their leisure physical exercise activities. Pain increasingly prevents them from achieving their goals. Psychological factors not only interact with neurobiological and immunological processes of pain, they play an important role in the development and maintenance of pain. Within that, expectations concerning the course of the disease and its treatment play a significant role. Study designs involving a placebo knee surgery show the high influence of these variables. The patients receiving the verum surgery do not report-as expected-less pain or better functioning than those receiving a placebo surgery. This significant influence of psychological factors may be clinically relevant. A positive patient-staff relationship-characterized by trust, warmth and empathy-is essential in order to achieve optimal therapeutic efficacy of a treatment. Every surgeon, pain physician, pain psychologist or pain physiotherapist is responsible for establishing a trusting interpersonal relationship between themselves and their patients.