Anesthesia for Joint Replacement: Spinal vs General, Nerve Blocks and Pain Control

For a knee or hip replacement, the anesthesia plan has two separate jobs. One is keeping you unconscious or numb during the operation. The other is controlling pain for the first days afterward, so you can get up, walk and start rehab. The second job is where most of the real choices are.

This guide explains spinal versus general anesthesia, the nerve blocks commonly used for knees and hips, what "multimodal" pain control means, how international guidelines treat opioids, and what to sort out before you fly home with prescribed pain medication. It is meant to help you have a better conversation with your anesthesiologist, not to replace it.

Spinal vs general anesthesia for joint replacement

With general anesthesia, you are fully unconscious and a machine usually supports your breathing through a tube or airway device. With spinal anesthesia (one type of neuraxial anesthesia), medication is injected into the fluid around the nerves in your lower back, which numbs you from roughly the waist down. Many people having a spinal also get sedation, so they doze through the surgery rather than lying there wide awake.

The most-cited consensus document on this question comes from ICAROS, the International Consensus on Anaesthesia-Related Outcomes after Surgery group. Its recommendations for primary hip and knee replacement were based on a systematic review and meta-analysis.¹ The group came down in favor of neuraxial anesthesia over general anesthesia for these operations.²

Two caveats. First, a consensus recommendation describes what tends to work better across large groups of patients; it does not mean general anesthesia is unsafe or wrong for you. Second, the pain-control guidelines discussed below (PROSPECT) do not pick between spinal and general for pain purposes. They address how to control pain whichever one you get.³⁴

If you take blood thinners, tell your surgeon and anesthesiologist early. Timing of when to stop and restart them affects whether a spinal or a nerve block is safe, and it also ties into clot prevention after surgery, covered in our guide to blood clots after joint replacement.

What multimodal pain control means

"Multimodal analgesia" means using several pain treatments that work in different ways, so each can be given at a lower dose and opioids are needed less. The PROSPECT working group, part of the European Society of Regional Anaesthesia and Pain Therapy, publishes procedure-specific recommendations for this, separately for knee and hip replacement.⁵

For both operations, the PROSPECT base layer looks similar:

• Acetaminophen (paracetamol) plus an NSAID or COX-2 inhibitor, started before or during surgery and continued afterward, unless you have a reason not to take them.³⁴
• A single intravenous dose of dexamethasone (a steroid) during surgery, which in trials reduced pain and nausea.³⁴
• A regional technique: a nerve block, local infiltration by the surgeon, or both, depending on the joint.³⁴
• Opioids held back for "rescue", meaning breakthrough pain the other layers do not cover.³⁴

The knee guideline also flags that older patients may be more prone to side effects from NSAIDs, so prescribers should watch closely.³ If you have kidney disease, a history of stomach ulcers or bleeding, or heart problems, raise it before surgery so the plan can be adjusted.

Some drugs that used to be routine are now on PROSPECT's "not recommended" lists. Gabapentinoids (gabapentin, pregabalin) are not recommended for either knee or hip replacement; the knee guideline cites minimal benefit and possible side effects, especially combined with opioids.³⁴ If one appears on your plan, it is fair to ask why.

Nerve blocks for knee replacement

Adductor canal block plus local infiltration

For total knee replacement, PROSPECT recommends a single-shot adductor canal block before surgery, combined with local infiltration analgesia (the surgeon injecting a local anesthetic mixture around the joint during the operation). The adductor canal block numbs nerves in the inner thigh. It gives pain relief similar to an older femoral nerve block while better preserving the strength of the quadriceps, the muscle you need to stand and walk.³

Because the adductor canal block mainly covers the front and inner part of the knee, it is meant to be paired with local infiltration rather than used alone.³

What the knee guideline advises against

PROSPECT does not recommend a femoral nerve block or a sciatic nerve block for knee replacement, because of their negative effect on functional recovery. It also advises against epidural analgesia, whose side effects can slow recovery, and against continuous infusions of local anesthetic into the joint, citing inconsistent benefit and a possible increase in infection risk.³

Low-dose intrathecal morphine, added to a spinal, can be considered only for hospitalized patients and only in the rare case where neither the adductor canal block nor local infiltration is possible. It causes itching, nausea and urinary retention and is not suited to same-day discharge.³

Nerve blocks for hip replacement: fascia iliaca and PENG

The hip guideline was updated more recently. Its current summary recommends a single-shot supra-inguinal fascia iliaca block for hip replacement through the posterolateral approach.⁴ It lists a PENG block (pericapsular nerve group block), given before surgery as a single shot, as a motor-sparing alternative with comparable effectiveness.⁴ "Motor-sparing" matters because you want your leg working well enough to get up the same day or the next.

Local infiltration by the surgeon "may be considered" when a block is not feasible or not appropriate, but the guideline describes its benefit as transient and modest. It does not support combining infiltration with a block, which may raise the risk of local anesthetic toxicity.⁴

Several other hip techniques are on the not-recommended list, including the infra-inguinal version of the fascia iliaca block, a PENG block given after surgery, lumbar plexus blocks and the anterior quadratus lumborum block (the last two because of side effects).⁴ Low-dose intrathecal morphine may be considered for inpatients who have a spinal.⁴

Note that this recommendation was written for the posterolateral approach. If your surgeon uses a different approach, ask what block they and the anesthesiologist usually pair with it. Our comparison of anterior versus posterior hip replacement explains the approaches themselves.

Opioid stewardship: what to expect and what to ask

Both PROSPECT guidelines reserve opioids for rescue pain rather than routine use.³⁴ That does not mean you will be denied pain medication. It means the plan should be built so that you need as little opioid as possible, for as short a time as possible.

The same thinking runs through orthopedic guidance before surgery. The AAOS knee osteoarthritis guideline gives a strong recommendation against oral opioids, including tramadol, for managing knee arthritis pain, citing more side effects without better pain or function.⁶ If you already take opioids every day, tell the surgical team well in advance. It changes how they dose you during and after surgery.

• Ask how many days of opioid tablets the discharge prescription covers, and what the plan is to taper.
• Ask which non-opioid medicines you should keep taking on a schedule, and for how long.
• Ask what to do if pain is not controlled once you are back home, and who you call.
• Keep opioids away from others in the house, and ask how to dispose of leftovers safely.

Questions to ask a Colombian anesthesiologist before you travel

If you are having surgery in Colombia, you may first meet the anesthesiologist on a video call or the day before surgery. Ask for a remote pre-anesthesia consultation, and send your medical records, medication list and any previous anesthesia problems ahead of time. You can confirm a Colombian clinician's professional registration through ReTHUS, the national health workforce registry.

1. Plan for the operation. Do you plan spinal or general anesthesia for me, and why? What happens if the spinal does not work?
2. Nerve block. Which block do you use for my joint and my surgeon's approach? Single shot or a catheter? When will it wear off?
3. Base medications. Will I get acetaminophen, an NSAID and dexamethasone? Are any unsafe for me given my kidneys, stomach or heart?
4. Opioids. Which opioid, if any, will I go home with, for how many days, and in what quantity?
5. My medications. Which of my regular medicines do I stop, and when? This includes blood thinners and diabetes drugs. If you take a GLP-1 medication, raise it specifically; our GLP-1 guide explains why.
6. Language. Will someone explain consent forms and discharge instructions in English, and will I receive them in writing?
7. Documents for travel. Will you give me a prescription and a medication summary I can show at the border?

Our broader list of questions to ask before joint replacement covers the surgeon and hospital side.

Traveling home with prescribed pain medication

Opioid pain medicines are controlled substances. Rules apply when you leave Colombia and when you enter your home country, and they differ between countries.

Returning to Canada

Health Canada lets travelers bring up to a 90-day supply of a prescription medication containing a controlled substance, based on the usual daily dose. It must be for you (or someone you are responsible for who is traveling with you) and prescribed by a practitioner.⁷ It must be in a container from a health care provider, labeled with your name, the prescriber's name, the drug name, the daily dose, and the form, quantity and strength.⁷ You must declare it on arrival. A doctor's note is optional, and the medication cannot be mailed into Canada.⁷

Health Canada's page does not separately address medication dispensed abroad, so if yours comes from a Colombian pharmacy, contact Health Canada's compliance section before you travel.⁷ It also advises checking the legality of your medication with the destination country's representatives before you leave Canada.⁷

Returning to the United States

We could not confirm U.S. Customs and Border Protection's current rules on imported controlled medications from a primary source for this article, so we are not stating quantity limits. Before you fly, check CBP's and the FDA's current traveler guidance. At minimum, keep the medicine in its original labeled container, carry the written prescription in your name, bring only what you need for recovery, and declare it.

If you want to see what a full joint replacement episode in Colombia would cost, including anesthesia and the hospital stay, you can request cost ranges.