Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Go to an emergency department after an injury if:
The joint looks deformed or out of place
You cannot put weight on the limb or use it
The limb becomes pale, blue, cold, numb, or weak
There is heavy bleeding or bone visible through a wound
You feel faint, confused, severely unwell, or short of breath
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Seek same-day urgent medical care if a joint becomes suddenly swollen, hot, very painful, or red, especially if you have a fever or feel unwell.
A joint infection must be considered quickly because early treatment can help prevent lasting joint damage.
You should also seek urgent assessment for sudden swelling if you have recently had joint surgery, an injection into the joint, a joint replacement, or an infection elsewhere in your body.
Arrange an appointment sooner if you have prolonged morning stiffness, unexplained weight loss, a new rash, or ongoing fatigue.
And for anyone, someone who:
is getting rapidly more short of breath, or has gained several pounds in a few days with swelling
3
Does any of this apply?
Book an appointment
Book a routine appointment if swelling lasts more than several days without improving, keeps returning, affects several joints, or interferes with sleep or everyday activities.
And for anyone, someone who:
has noticed a lump, a mole that has changed, or unexplained weight loss
Every sign above is quoted from the sofidex article on Joint swelling. If you are not sure, err upward — it is always reasonable to be checked.