In short: a spinal anaesthetic numbs you from the waist down while you stay awake or lightly sedated; a general anaesthetic makes you unconscious for the operation. Both are widely used for hip and knee replacement, and either can be combined with a nerve block. Your anaesthetist recommends an approach based on your health, the operation and the surgical team's needs, and the decision is made with you.
The two main options
Option one
Spinal anaesthetic
How it is given. You sit up or lie on your side while the anaesthetist places a very fine needle in your lower back and injects local anaesthetic, often with other pain-relieving medicine, into the fluid around the spinal nerves. healthdirect describes it as uncomfortable rather than painful.
What you feel. Warmth in the legs or buttocks, then numbness and heavy legs that you cannot move. The anaesthetist checks the numb area, often with something cold, before surgery starts. The Australian Society of Anaesthetists (ASA) says surgery can usually begin within 5 to 10 minutes.
Awake or sedated. You can stay awake, or have sedation so you are relaxed and drowsy. A screen keeps the operation out of view.
How long it lasts. The numbness and heaviness usually last a few hours and wear off gradually. How long depends on the medicines and the dose used.
Option two
General anaesthetic
How it is given. A small plastic tube (cannula) is placed in a vein, you may breathe oxygen through a mask, and anaesthetic medicines are given through the cannula until you are unconscious.
What happens while you are asleep. Once you are fully asleep, a breathing tube is placed to protect your airway. The anaesthetist stays with you and monitors you throughout.
Waking up. You wake in the recovery room, often drowsy. Discomfort, pain or nausea are common and are treated with regular medicines. A dry or sore throat or a headache usually passes in one to two days, according to the ASA.
Combined with a block. A nerve block is often added so the joint stays comfortable after you wake.
Why regional anaesthesia is so common for joint replacement
Regional anaesthesia numbs one part of the body. It includes spinal anaesthetics and nerve blocks. ANZCA, the college that trains specialist anaesthetists, describes it as the most common form of anaesthesia for joint replacement, and the ASA notes that many hip and knee replacements are done under a spinal. ANZCA says the aim is good pain control with less sedation, nausea and vomiting.
That does not make a spinal right for everyone. ANZCA lists what your anaesthetist weighs up:
- your past experience of surgery and anaesthesia
- your general health and fitness, including heart and lung conditions
- any reactions or allergies to medicines
- the risks of each type of anaesthetic for you
- what the surgical team needs for the operation
- your own preferences.
Joint replacement is often done in older people, many of whom have other conditions, such as high blood pressure or heart problems, that need to be assessed first. Read getting ready for joint replacement for how that assessment works.
Where nerve blocks fit
A nerve block numbs the nerves that supply the joint and can keep it comfortable for hours after the operation. The ASA says blocks are often combined with a spinal or a general anaesthetic, mainly for pain relief afterwards. If you are having one, ask how long the numbness is expected to last and how to look after the limb. Our guide to nerve blocks covers both.
If you are awake: what to expect
- You will not see the operation. A drape or screen is set up between you and the surgical team.
- You may be aware of sounds and movement. If you would prefer not to be, ask about sedation, or whether you can listen to music through headphones. Hospitals differ in what they allow.
- Sedation is not sleep. You may drift in and out and remember snatches of conversation.
- You can speak to the anaesthetist at any time. They stay with you throughout.
Risks to talk through
Serious complications are uncommon with either option, but every anaesthetic has risks, and some depend on your health. healthdirect notes that risks are higher for people who are older, are obese, smoke, or have diabetes, heart disease or lung disease. Your anaesthetist can tell you how the figures apply to you.
| How often | Spinal anaesthetic | General anaesthetic |
|---|---|---|
| Usually minor and short-lived | A drop in blood pressure, shivering, itch, nausea, bruising and difficulty passing urine (a catheter may be needed). Rarely, a headache caused by a leak of spinal fluid, which usually settles with rest and can be treated if it does not. | Drowsiness, tiredness, nausea and vomiting, sore throat, headache, muscle aches, bruising and disturbed sleep. |
| Rare but serious | Nerve damage, which is sometimes permanent; infection; bleeding; a block that spreads higher than intended; severe allergic reaction. | Severe allergic reaction, severe bleeding, heart attack, stroke, seizure, pneumonia or other lung damage, and damage to the vocal cords. |
healthdirect puts the chance of a serious complication from a spinal at about 1 in 50,000. The ASA describes the serious complications of anaesthesia for hip and knee replacement, including death, as very rare.
After a spinal: what to report
The numbness wears off over a few hours and you may feel tingling as it does. Ask for help the first time you get out of bed, because your legs may still be weak. The ASA advises telling your anaesthetist or nurse about:
- a severe headache that does not go away
- new, unexplained pain in your back where the injection was, or in your buttocks or legs, especially with a fever or chills
- numbness or weakness in your legs that is new or getting worse
- difficulty passing urine, or loss of bowel control.
Other bone and joint operations
- Shoulder replacement. The ASA says most can be done with a nerve block alone or with a general anaesthetic plus a block. Your arm may stay numb and hard to move for some time afterwards.
- Spine surgery. Operations on the spine are done under a general anaesthetic. You may be turned face down once you are asleep, and the ASA notes your face and eyes can look puffy for a while afterwards.
- Knee arthroscopy. healthdirect notes that different types of anaesthetic are possible, the operation usually takes 30 to 45 minutes and you should usually be able to go home the same day.
Making the decision together
ANZCA’s position on consent is that your anaesthetist should explain the options, the risks that matter to you and the alternatives, and that written information like this page is not a substitute for that conversation. Bring your questions; our list of questions to ask your anaesthetist is a good starting point.
Common questions
Will I be awake during my joint replacement?
Only if you want to be and your anaesthetist agrees. With a spinal you can stay awake, or you can have sedation through a drip so that you are relaxed and drowsy. Sedation is not a general anaesthetic, so you may remember parts of the operation, particularly conversations. If you would rather be unconscious, say so at your assessment and ask what that would mean for you.
Can I ask for a general anaesthetic instead of a spinal?
Yes, you can raise it. healthdirect notes that if you decline a spinal, your anaesthetist can suggest alternatives, such as a general anaesthetic or a nerve block. Your anaesthetist will explain how the options compare for your health and your operation, and the final plan is agreed with you.
Why might I need a urinary catheter?
A spinal can make it hard to pass urine for a while, and a thin tube (catheter) may be used to drain the bladder until it settles. For some operations a catheter is also placed after you are anaesthetised, as part of the extra monitoring. Tell the nurses if you cannot pass urine once you are back on the ward.
Sources
- ANZCA. Anaesthesia for joint surgery (patient information). Page modified 30 Sep 2025.
- Australian Society of Anaesthetists. Anaesthesia for hip and knee replacement surgery (patient information pamphlet). Last reviewed 12 Mar 2024.
- Australian Society of Anaesthetists. Epidural and spinal anaesthesia and analgesia (patient information pamphlet). Last reviewed 12 Mar 2024.
- healthdirect Australia. Spinal anaesthetic. Last reviewed Jan 2026.
- Australian Society of Anaesthetists. Anaesthesia for shoulder joint replacement surgery (patient information pamphlet). Last reviewed 12 Mar 2024.
- Australian Society of Anaesthetists. Anaesthesia for spinal surgery (patient information pamphlet). Last reviewed 12 Mar 2024.
- healthdirect Australia. Arthroscopy of the knee. Last reviewed Jan 2026.
- ANZCA. PS26(A) Position statement on informed consent for anaesthesia or sedation. April 2021.
- Written by
- Altitude Creative, health content team, on behalf of Dr Walid Aly
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How this guide is written, reviewed and corrected: editorial policy.
In an emergency, call 000. This information is general and does not replace advice from your treating practitioner.