A joint that becomes suddenly very painful, hot or swollen after PRP needs prompt medical assessment. Temporary soreness can occur after an injection, but worsening symptoms, difficulty moving the joint or feeling unwell should not be assumed to be a normal treatment response.
If you have these symptoms now, seek urgent medical help today through an urgent GP appointment or NHS 111. If you cannot obtain timely assessment, attend A&E. Call 999 for signs of sepsis such as confusion, severe breathing difficulty, blue, pale or blotchy skin, or collapse. Do not wait for a routine clinic message.
This guide explains the distinction between ordinary aftercare and symptoms that need an examination. It is not a way to rule out infection at home. PRP is an elective treatment, and protecting the joint takes priority over continuing a course or keeping to a recovery timetable.
Illustrative photograph from the existing blog image library.
Why a change in the joint deserves attention
Platelet-rich plasma is prepared from your own blood, but treatment still involves a needle entering the body. Using an autologous preparation does not remove the possibility of complications. Patient information on musculoskeletal PRP describes temporary pain, bruising and swelling, alongside risks including infection and nerve injury.
The important question is not simply whether some discomfort is expected. It is whether the symptoms fit the individual procedure and are following the course explained by your clinician. A joint that is increasingly painful, difficult to move or newly hot and swollen needs a different response from a small bruise at a needle site.
A remote description or photograph cannot safely distinguish every cause. The timing of the injection, the precise location, your general health and a physical examination may all matter. Clear aftercare should make it easier to obtain the right assessment, rather than encourage you to tolerate a worrying change.
The symptoms that should prompt urgent help
The NHS guidance on septic arthritis describes sudden severe joint pain, difficulty moving or putting weight on the joint, heat, swelling and skin colour changes. A high temperature may occur, but not everyone has a fever. Redness can be less obvious on brown or black skin.
Seek urgent assessment if the joint becomes substantially more painful, movement is markedly restricted, swelling increases or you feel hot, cold, shivery or generally unwell. Tell the clinician that you recently had a joint procedure. Do not wait for all the symptoms to appear together or for a particular number of days to pass.
New discharge from the injection site, spreading skin changes or pain that is worsening rather than settling should also be reported promptly. An appointment for a future treatment session is not an adequate response to a current concern about infection. The appropriate route depends on how unwell you are and how quickly you can be assessed.
If you are uncertain, NHS 111 can help direct you. Severe symptoms or an inability to obtain timely urgent assessment may require A&E. If you feel too unwell to travel safely, do not drive yourself. Emergency symptoms need an emergency response, not a routine booking enquiry.
What septic arthritis means
Septic arthritis is an infection within a joint. It needs prompt treatment because an untreated infection can damage the joint and can cause serious illness. It is different from the non-infectious inflammation associated with conditions such as osteoarthritis, gout or some treatment reactions.
A hot swollen joint has several possible causes. The purpose of urgent assessment is to establish which explanation fits, including whether infection needs to be excluded. The fact that a symptom started after an injection does not, by itself, prove that the injection caused an infection. Equally, that uncertainty is not a reason to delay assessment.
The British Society for Rheumatology's published scope for updated hot-swollen-joint guidance identifies recent joint injection among relevant risk factors. This publication is a guideline-development scope, not a completed new treatment guideline. It supports the importance of prompt assessment without providing a PRP-specific infection rate.
No reliable percentage from a different injection, a different treatment setting or an unrelated study should be presented as your personal risk. Your own procedure and health history need to be considered. A reassuring description of PRP as 'natural' does not answer the clinical question raised by a newly hot swollen joint.
Why no fever or a normal blood test is not enough
Fever can help alert a clinician to infection, but its absence does not exclude septic arthritis. This is particularly important when someone expects a thermometer reading to settle whether they should seek help. Pain, swelling, loss of movement and the overall clinical picture still matter.
Blood tests may be part of the assessment. The specialist publication notes that normal inflammatory markers do not exclude septic arthritis. An earlier normal blood result, especially one taken before the symptoms developed, should not be used to dismiss a new change in the joint.
Similarly, an X-ray can be useful for some questions without ruling out an early joint infection. The investigation is chosen to answer the suspected problem. A previous diagnosis of arthritis or a recent scan does not remove the need to reassess a new, rapidly changing symptom pattern.
The practical benefit of a clinical review is that these pieces of information can be considered together. It avoids making a decision from one reassuring detail while overlooking a change in function, a recent procedure or the way the symptoms are progressing.
Once urgent concerns have been addressed, discuss whether further PRP is appropriate.
What an urgent assessment may involve
A clinician will usually ask when the procedure took place, which joint was treated and how the symptoms have changed. Your medicines, recent infections, diabetes, immune conditions, previous joint surgery and any joint replacement are relevant. Bring the procedure information if it is readily available, but do not delay urgent care to obtain records.
The examination considers the joint, the surrounding skin, movement, weight-bearing and how well you are overall. Blood tests and imaging may be needed. If septic arthritis is suspected, hospital assessment and sampling fluid from the joint may be part of the investigation. The fluid can be examined for infection and other causes, including crystals.
These are clinician-led decisions. A clinic photograph, an online symptom score or a home treatment trial cannot replace them. Do not try to drain a swollen area, restart an old antibiotic prescription or take someone else's antibiotics. Tell the assessing team about any medicine you have already taken.
If infection is diagnosed, treatment commonly involves hospital care, antibiotics and drainage of the joint. The exact treatment and follow-up depend on the findings. This article does not prescribe an antibiotic, suggest a home treatment course or promise a particular recovery time.
Other causes still need the right diagnosis
Gout, calcium pyrophosphate crystal arthritis, bleeding into the joint and other inflammatory problems can also cause acute swelling and pain. They can resemble infection. A previous episode of gout does not establish that a new hot joint has the same cause, and a familiar symptom should not automatically be managed from memory.
A sore calf or swelling extending beyond the joint can raise a separate question. NHS guidance on deep vein thrombosis advises urgent help for symptoms such as pain and swelling in one leg. Leg symptoms with chest pain or breathlessness need emergency assessment through 999 or A&E.
A Baker's cyst can also cause symptoms around the back of the knee and calf. These different explanations cannot always be separated without an examination and, when indicated, further tests. Do not assume calf swelling is simply fluid moving after an injection.
The aim is an accurate diagnosis, not a label chosen because it seems least worrying. Once the cause is clear, the treatment and activity advice can be specific to it. That is more useful than applying a general PRP recovery schedule to every new symptom.
Medicines and health conditions that matter
Tell the assessing clinician about anticoagulants, prescribed aspirin, steroids, medicines that suppress the immune system and any antibiotics. These can affect the assessment and management. Do not stop a prescribed medicine on your own to make further PRP possible or because you suspect it caused the swelling.
Diabetes, rheumatoid arthritis, a weakened immune system and a joint replacement are among the risk factors described by the NHS. They are reasons to provide a clear history, not reasons to wait for more severe symptoms. A prosthetic joint with new concerning symptoms needs particular attention from the appropriate hospital team.
The absence of these conditions does not rule out a complication. Conversely, having one does not prove infection. A careful assessment treats risk factors as part of the picture and then investigates according to the symptoms and examination.
Planning further treatment after the acute concern
Do not proceed with another injection into a joint that has an unexplained acute problem. The treating clinician needs to understand what happened, review the findings and decide whether further treatment is appropriate. The outcome may be a revised rehabilitation plan, a different treatment, specialist advice or no further PRP.
For a non-urgent consultation at The London PRP Clinic, the value is a suitability decision tied to the diagnosis, the evidence and your health, rather than an automatic commitment to a course. Any proposed treatment should include a clear account of expected benefit, uncertainty, alternatives, risks and the relevant fee before you decide.
Arrange a non-urgent consultation to review the next step after assessment.
Frequently asked questions
Is a hot swollen joint normal after PRP?
Some temporary soreness, bruising or swelling can occur after an injection. A joint that becomes very painful, increasingly hot or swollen, difficult to move, or associated with feeling unwell needs urgent assessment. Do not decide it is a normal treatment response without appropriate clinical advice.
Can I have a joint infection without a fever?
Yes. The NHS states that not everyone with septic arthritis has a fever. Sudden severe pain, swelling, skin changes and difficulty moving or bearing weight are still reasons to seek urgent help. A normal temperature is not clearance to wait.
Should I wait until the clinic replies on WhatsApp?
Not if you have symptoms suggesting an urgent complication. Seek urgent medical help through an urgent GP appointment or NHS 111, and attend A&E if timely assessment is not available or symptoms are severe. Call 999 for emergency symptoms. A routine clinic enquiry is not an emergency service.
Does a normal CRP blood test rule out septic arthritis?
No. Normal inflammatory markers do not exclude septic arthritis. The history, examination and appropriate investigations need to be considered together. An old blood test taken before the current symptoms is not a reliable answer to a new hot swollen joint.
What if the swelling is mainly in my calf?
Pain and swelling in one leg can require urgent assessment for a blood clot or another cause. Seek urgent GP or NHS 111 advice. If leg symptoms occur with chest pain or breathlessness, call 999 or go to A&E. Do not assume calf swelling is ordinary PRP aftercare.
Can I continue my PRP course once the swelling settles?
That decision needs the treating clinician's review. Improvement alone does not establish what caused the problem or whether another injection is appropriate. The diagnosis, any investigation results, your medicines and the treatment alternatives should be considered before further treatment.
A clear distinction between urgent care and future planning
If a joint is suddenly hot, swollen and very painful now, the next step is urgent medical assessment. Once that concern has been assessed, a planned consultation can consider whether PRP still has a role in your care. These are separate decisions, with different timescales.
Contact The London PRP Clinic for non-urgent PRP suitability planning after assessment.
Related reading includes driving and arranging the journey home after PRP and infection or dental treatment before PRP.
Sources
- NHS, septic arthritis, symptoms and urgent medical help.
- NHS, sepsis, emergency symptoms and action.
- NHS, deep vein thrombosis.
- British Society for Rheumatology, published scope for updated management guidance on a hot swollen joint.
- Musculoskeletal PRP patient information, risks and when to seek help.
General patient information. It cannot diagnose a complication or replace urgent medical assessment.