The goal of this randomized clinical trial is to investigate the postoperative recovery following hip and knee arthroplasty procedures depending on the use of either spinal anaesthesia (SA) or general anaesthesia (GA).

The main questions are:

• Are more patients able to be safely mobilized within 6 hours postoperatively when using GA compared to SA?
• Does postoperative pain, nausea and vomiting, dizzyness, occurence of delirium and urinary retention differ between the anaesthetic methods?

Participants, scheduled for total hip, total knee and unicomartmental knee arthroplasty, will be randomized to recieve spinal anaesthesia or general anaesthesia in relation to surgery. At 6 hours postoperatively a physiotherapist will conduct a 5-meter walking test to evaluate whether the participant can be safely mobilized.

Inclusion Criteria:

• Clinical and radiological hip or knee osteoarthritis meeting the indications for primary total hip, total knee, or unicompartmental knee arthroplasty.
• ≥18 years of age.
• Able to speak and understand Danish
• Able to give informed consent and must be cognitively intact.

Exclusion Criteria:

• Lives in an institution.
• Uses walking aid such as a walker or a wheelchair.
• Terminal illness.
• Has contraindications for either general or spinal anaesthesia.
• Has objections to receiving either general or spinal anaesthesia.
• Requires anxiolytics as premedication prior to anaesthesia.
• Traumatic aetiology as a basis for surgical indication.
• Altered pain perception and / or neurologic affection due to diabetes or other disorders.
• Daily preoperative use of opioids > 30 mg of morphine milligram equivalents (MME).
• Standard primary arthroplasty procedure is evaluated not to be suitable.
• Women considered fertile but without sufficient birth control.

Physcians and nurses in the surgical department are not able to be blinded. But outcome assesors (ie. physiotherapists, research personel) are not aware of the treatment allocation.