The development and implementation of "fast-track" principles in total knee and hip arthroplasty have resulted in early recovery and rehabilitation alongside a reduced length of hospital stay. This without a concomitant increase in morbidity or readmissions for medical or surgical complications and with reduced mortality. However, only little is known about function in the subacute period after arthroplasty, and there is a need for further data on physical and psychological functioning following discharge from hospital.This to ensure, that the positive results from the perioperative setting are carried forward in the subacute phase.

Data will be published in three papers:

1. "Physical function and related factors following discharge from THA and TKA" Luna IE, Kehlet H, Aasvang EK.
2. "Postoperative hypoxemia following fast-track hip and knee arthroplasty" Luna IE, Kehlet H, Aasvang EK.
3. "Cognitive dysfunction after fast-track hip- and knee arthroplasty - prevalence and related factors". Luna IE, Kehlet H, Aasvang EK.

Inclusion Criteria:

• Primary total hip or knee arthroplasty
• Age 55 to 80 years

Exclusion Criteria:

• Deficient written or spoken danish
• Alcohol abuse (>21 U per week)
• Immunocompromised
• Anticoagulant therapy
• ASA class 4-5
• Functional impairment from psychological or neurological disease
• Sleepapnea

Patients with hip or knee osteoarthritis referred for total joint arthroplasty.