The short version

The injection itself takes well under a minute. Most of the appointment is positioning, cleaning and talking.
You almost certainly do not need to stop your blood thinner. In 1,050 consecutive procedures on direct oral anticoagulants there were no bleeding complications.
It hurts less than people expect, and differently. The sting is the numbing medicine, not the injection.
Expect the joint to feel odd for a day or two. That is normal and is not a sign anything went wrong.

Almost everyone arriving for a first injection has the same picture in their head, assembled from a stranger's story and an internet search. The real thing is shorter and duller than that, which is worth knowing in advance.

What should you do beforehand?

Very little, and that surprises people.

Eat normally. There is no fasting requirement for a joint injection.
Take your usual medications. Including, in almost all cases, blood thinners — see below.
Wear something that gives access to the joint. Shorts for a knee, a loose sleeve for a shoulder. It saves a gown.
Bring your medication list, particularly if you have diabetes, since blood sugar will rise for a few days.
Plan to drive yourself. No sedation is involved, and most people drive home without difficulty.

Do you need to stop a blood thinner?

Usually not, and stopping carries its own risk.

A review of 1,050 consecutive joint aspirations and injections in patients taking direct oral anticoagulants found no bleeding complications at all, and concluded there is no need to withhold anticoagulation before the procedure. Earlier work established similar safety for warfarin, with only a small increase in bleeding risk.

This is not a decision to make by yourself either way — tell whoever is performing the injection what you take, and let them decide. But do not assume you are supposed to stop, and do not stop on your own initiative.

What happens in the room?

First Positioning
The joint gets placed in whatever position opens the target — a slightly bent knee, an arm rotated a particular way. This matters more than it looks like it does, and it is worth staying where you are put.
If ultrasound is used A look before anything else
Gel and a probe, no needle yet. This is where an unexpected effusion or a tendon in the path turns up, and occasionally changes the plan.
Then Cleaning the skin
Antiseptic, which is cold. This step is the main defence against the one serious complication, so it is not rushed.
The part that stings Numbing medicine
A small amount of local anaesthetic into the skin. It stings for a few seconds — genuinely the worst part of the procedure for most people — and then the area goes numb.
Under a minute The injection itself
Pressure rather than sharpness. Some joints produce a brief ache as the fluid goes in, particularly tight ones. If there is a lot of fluid in the joint it may be drawn off first, which usually feels like relief.
Last A plaster, and a few minutes sitting
That is it. No stitches, no dressing beyond a small plaster.

How much does it hurt?

Less than most people brace for, and the discomfort is not where they expect it.

The sting is the local anaesthetic going in, and it lasts a few seconds. The injection that follows is mostly pressure. People routinely say afterwards that the anticipation was worse than the event, which is not reassurance — it is the most common thing I hear.

Two things genuinely make it more uncomfortable: a very tight or inflamed joint, where the fluid has nowhere easy to go, and tensing up, which makes everything harder. Breathing normally and letting the limb go heavy helps more than it sounds like it should.

The thing that reduces pain most

Telling someone exactly what is about to happen, in order, before touching them. A patient who knows the sting is coming and that it lasts four seconds experiences it differently from one who does not.

That is a practice habit rather than a trial finding. But of everything I have changed over several thousand of these, narrating the procedure has done more for how it is tolerated than any change in technique.

Afterwards

The first hour or two often feels unusually good, because the local anaesthetic is still working. That is not the steroid — the steroid takes days. When the numbness wears off the joint may feel ordinary again, or briefly worse, and neither means anything about whether it will work.

Take it easy for a day or two. Not bed rest — just avoid testing the joint hard to see whether it worked.
Ice helps if the joint is sore that evening.
Expect the real answer around day three to seven, not on the drive home.
Know the difference between an expected flare and the rare complication that needs same-day evaluation.

This article is general education about what a joint injection involves. It is not medical advice, does not create a patient–provider relationship, and cannot account for an individual situation. Practices vary between clinicians, and decisions about your own medications — including anticoagulants — should be made with the clinician performing the procedure rather than on the basis of a website. See the editorial policy for how this content is written and reviewed.

Sources

Yui JC, Preskill C, Greenlund LS. Arthrocentesis and joint injection in patients receiving direct oral anticoagulants. Mayo Clinic Proceedings 2017;92(8):1223–1226. 1,050 consecutive procedures, no bleeding complications. Retrieved via PubMed.