Spinal vs General Anaesthetic for Hip and Knee Replacement:
What to Expect

Why Most Patients Worry More About the Anaesthetic Than the Surgery

It is one of the most common things patients quietly admit at their first consultation. "I'm not so worried about the operation itself — it's the anaesthetic that frightens me." If you feel the same, you are not unusual, and you are not being irrational.

The anxiety usually centres on the same handful of fears: losing consciousness in a roomful of strangers, not being in control of what happens to your body, the idea that something might go wrong while you are unaware, and — particularly with spinal anaesthesia — the worry of being awake during the procedure itself.

The reassuring truth is that modern anaesthesia for hip and knee replacement is genuinely different from what it was even ten years ago. Most of those changes have made the experience easier, safer, and more predictable. The aim of this article is to explain, honestly, what is now standard practice — and why most patients tell us afterwards that the experience was nothing like what they had feared.

The Two Main Approaches

There are two broad ways of anaesthetising someone for hip or knee replacement: spinal anaesthesia (often combined with sedation) or general anaesthesia. In modern UK private practice, the great majority of joint replacements are performed using the first approach.

Spinal anaesthesia — what's actually used

In real-world practice, "having a spinal" is not a single technique; it is a layered combination designed to do three things at once: keep you calm and comfortable, make the operation completely painless, and give you smooth, controlled pain relief afterwards.

The combination is more effective than any of these techniques alone. The sedation removes anxiety and time-awareness, the spinal removes all sensation of the surgery itself, and the local infiltration means your post-operative pain is easier to manage with less reliance on strong opioid medication.

General anaesthesia

General anaesthesia produces full unconsciousness. Drugs are given through your cannula, you fall asleep within seconds, and the consultant anaesthetist supports your breathing throughout the operation. You wake up in the recovery room afterwards with no memory of any part of the procedure. Modern general anaesthesia is extremely safe and, when it is the right choice for a particular patient, it is an excellent option.

Why Spinal Has Become the Standard for Hip and Knee Replacement

The shift from general to spinal anaesthesia as the default for major joint replacement has happened gradually over the last decade or so, and it has been driven by consistent research evidence rather than fashion. For most patients undergoing hip replacement or knee replacement, spinal anaesthesia is associated with measurable advantages:

• Less blood loss during the operation, meaning blood transfusions are very rarely needed
• Significantly lower rates of post-operative nausea and vomiting
• Earlier mobilisation — many patients can stand and take their first steps within hours of returning to the ward
• Lower rates of chest infection and other breathing complications, particularly relevant for patients over 65
• Less strain on the heart and circulation — important for patients with existing cardiac or respiratory conditions
• A clearer head on the day of surgery, with no anaesthetic "fog" or grogginess to push through before recovery can begin in earnest

For these reasons, every modern enhanced recovery pathway for hip and knee replacement in the UK now specifies spinal anaesthesia as first-line wherever it is suitable for the patient.

"Will I Be Awake During My Operation?" — The Honest Answer

This is the single most common concern patients raise about spinal anaesthesia, and it deserves an honest answer rather than a reassuring brush-off.

Strictly speaking, you are not under general anaesthesia during a spinal — so in that narrow technical sense, you are not "asleep". But this is very different from what most people imagine when they hear the word "awake". With the sedation that accompanies a modern spinal anaesthetic, the great majority of patients doze through the operation. Many sleep entirely. Very few have any clear, continuous memory of the surgery taking place.

What actually happens is this. You are taken into the operating theatre on a trolley. The consultant anaesthetist administers the spinal in the lower part of your back — a small sting from the local anaesthetic injection beforehand, then usually nothing more than a brief sensation of pressure. Within a few minutes your legs become heavy and warm, and you stop being able to feel them. Sedation is then given through the cannula in your hand, and you become drowsy. A drape (a sterile screen) is placed across your chest, blocking your view of the surgical field entirely. The consultant anaesthetist sits at the head end of the table for the entire operation, monitoring your blood pressure, heart, and breathing continuously, and adjusting the sedation as needed.

The most common feedback from patients afterwards is that they were genuinely surprised by how unremarkable the experience was. They expected to be anxious. They weren't. Many doze. Some chat quietly with the anaesthetist. A small number remember nothing at all and assume they had a general anaesthetic.

Sedation tailored to you

One of the most reassuring features of modern sedation is that the depth is not fixed. Sedation can be titrated — increased or eased back — at any point during the operation, in response to how you are feeling. If you find yourself becoming aware of background sounds in the theatre and you would prefer to be more deeply asleep, the consultant anaesthetist can deepen the sedation immediately. If you would rather feel a little more present, that is equally possible. The level is responsive to you throughout, not chosen at the start and left alone.

For patients who would simply prefer to be unaware of the entire experience, deeper sedation is a perfectly reasonable choice. Many patients, on the other hand, find a lighter level perfectly comfortable — and the option remains theirs.

Nausea, Sickness, and Recovery Comfort

One of the most under-appreciated advantages of spinal anaesthesia is the dramatic reduction in post-operative nausea and vomiting (PONV). Patients tend to focus their pre-operative worry on pain, not nausea — but anaesthetists know that for many people, nausea is what makes the first day after surgery genuinely unpleasant. It makes it harder to eat, harder to take pain medication reliably, harder to take those first few important steps with the physiotherapist, and harder to sleep that first night.

Because spinal anaesthesia involves far less anaesthetic drug entering the body's general circulation than a general anaesthetic does, post-operative nausea is significantly less common. Many patients eat a normal evening meal on the day of their surgery — something that is far less likely after a general anaesthetic.

Other comfort advantages of spinal include no sore throat from a breathing tube, no jaw or dental discomfort, no muscle aching from anaesthetic-paralysing drugs, and far less of the heavy "anaesthetic hangover" that can take half a day to clear after general anaesthesia. For older patients in particular, this can be the difference between an easy first 24 hours and a difficult one.

When General Anaesthetic Is the Right Choice

Spinal anaesthesia is the modern default — but it is not the right answer for every patient. There are several legitimate reasons why a general anaesthetic may be the better option, and patient preference is one of them.

• Severe anxiety, claustrophobia, or strong patient preference. Being in any way present during your own surgery — even calmly sedated — is not the right experience for everyone. If the idea genuinely distresses you, that is a reasonable medical reason in itself to choose general anaesthesia. Your anaesthetist will not judge or pressure you.
• Previous extensive lumbar spinal surgery — particularly long fusion constructs — can make it technically difficult or impossible to safely perform a spinal injection (see our related article on hip resurfacing after spinal fusion).
• Certain blood-thinning medications that cannot be safely paused before surgery may rule out neuraxial techniques because of an increased risk of bleeding around the spinal canal.
• Significant spinal anatomy issues — severe scoliosis, previous spinal infection, or other anatomical considerations.
• Specific medical conditions — certain neurological conditions, severe valve disease, or rare drug allergies may favour a general anaesthetic.

For patients in any of these categories, modern general anaesthesia is safe and effective. Your consultant anaesthetist will combine it with regional techniques (such as nerve blocks) and the surgeon's local infiltration to give you excellent post-operative pain relief, regardless of how the main anaesthetic is delivered.

Spinal vs General — Side by Side

The Risks, Addressed Honestly

Every anaesthetic carries some risk. The honest position is that both techniques are extremely safe in modern hospital practice, but neither is risk-free, and you should know what the genuine considerations are.

Spinal anaesthetic — the main considerations

• A temporary headache afterwards ("post-dural puncture headache") — uncommon, and treatable when it does occur
• A drop in blood pressure during the procedure — managed easily and routinely by the anaesthetist with fluids and medication
• Difficulty passing urine for a short time afterwards — almost always settles within a day
• Persistent nerve symptoms — very rare
• Bleeding or infection around the spinal canal — extremely rare

General anaesthetic — the main considerations

• Sore throat or, rarely, dental damage from the breathing tube
• Higher rates of post-operative nausea and vomiting than with spinal anaesthesia
• Temporary cognitive fogginess, particularly in older patients — usually short-lived
• Awareness during anaesthesia — extremely rare with modern monitoring
• Allergic reactions to anaesthetic drugs — uncommon

Risks common to any anaesthetic — cardiovascular events, breathing complications, drug reactions — exist with both techniques, but the absolute rates in elective joint replacement at modern centres are very low, and lower today than at any time in the history of anaesthesia.

How the Decision Actually Gets Made

Reassuringly, you are not asked to make this decision alone or in a vacuum. The process unfolds in stages, and there are several points at which your concerns can be heard and your questions answered.

In the weeks before surgery, you will attend a pre-operative assessment. Your full medical history is reviewed, your medications are checked, and any necessary investigations — blood tests, ECG, cardiac or respiratory review — are arranged. All of this information is then made available to your consultant anaesthetist before the day of surgery, so they can plan ahead.

On the morning of your operation, you will meet your consultant anaesthetist face-to-face in the admission area. They will introduce themselves, walk you through the proposed plan, explain why they are recommending one approach over the other, and answer any questions you have. The final decision is a shared one — between you and them — and nothing happens without your understanding and consent.

This is the moment to raise anything you are uncertain about. Patients often arrive feeling they cannot ask "obvious" questions. The truth is the opposite: the anaesthetic team's job is to make sure you feel comfortable with the plan before you go to theatre. No question is too small.

Questions to Ask Your Anaesthetist

Patients often find it helpful to write a few questions down in advance. The following are reasonable starting points:

1. Which type of anaesthetic do you recommend for me, and why?
2. If I'm having a spinal, what level of sedation do you suggest? Can I have more if I find I want it during the operation?
3. What is the plan for pain relief in the first 24 hours after surgery?
4. Are there any of my regular medications I need to stop, and when?
5. Are there any specific anaesthetic risks for me given my medical history?
6. How long will it take me to fully recover from the anaesthetic itself, separately from the surgery?