Expected, uncommon, and the three that warrant a call.

RECOVERY / SIDE EFFECTS

PRP has a favorable safety profile, and that is precisely why it deserves a careful page rather than a reassuring paragraph. A treatment described as risk-free is a treatment nobody has examined properly.

Why the baseline risk is low

The preparation is autologous — drawn from you, concentrated, returned to you within the hour. There is no donor material, so no transmission risk and no immune rejection. There is no drug, so no pharmacological adverse effect, no systemic exposure and no interaction with your other medications. What remains is the risk of any injection procedure, plus the specific properties of the tissue being treated.

Expected, uncommon, and the three that warrant a call

The wording below carries the meaning; the color is a second channel on top of it, not instead of it.

Infection risk, stated precisely — and why BMAC differs

This is worth being exact about, because the two treatments are frequently discussed as though they carry the same risk and they do not.

PRP has a low infection risk, and prophylactic antibiotics do not help it. The procedure is a venous draw and a soft-tissue injection under sterile conditions. Adding antibiotics to a low-risk soft-tissue injection contributes side effects and resistance pressure without contributing protection, so we do not use them.

Bone marrow aspirate concentrate carries an infection risk of different consequence rather than higher frequency, and that risk is mitigated with antibiotics. Pooled randomized data across six trials and 860 patients puts BMAC complication rates at about 42% against 41% for comparator injections — no significant difference, with effusion the most common event. What changes the antibiotic decision is severity, not likelihood: an infection seeded at or near bone is a longer and harder problem than a soft-tissue one. The reason is the harvest: BMAC requires aspirating marrow from the iliac crest, which is a deeper and more invasive entry, and an infection seeded in or near bone is a far more serious problem than a soft-tissue one. Antibiotic prophylaxis is appropriate there and is used.

Two different procedures, two different risk profiles, two different answers on antibiotics. Anyone offering both under a single consent conversation is not describing them accurately. The full comparison is here.

What raises your individual risk

• Poorly controlled diabetes — both infection risk and poorer healing
• Active nicotine use — impaired perfusion in tissue that already has little
• Immunosuppression, whether from disease or medication
• Anticoagulation, which raises bruising and needs individual planning
• Any active infection elsewhere in the body at the time of treatment

The risk of the alternatives, for comparison

Risk is only meaningful against what you would otherwise do, and the comparators are not risk-free either.

• Repeated corticosteroid injection — cartilage loss with repeated intra-articular use, tendon weakening and rupture, fat pad atrophy, and transient glycemic disturbance that matters in diabetes.
• Long-term NSAID use — gastrointestinal, renal and cardiovascular risk that accumulates quietly over years.
• Surgery — anesthetic risk, infection, thromboembolism, and a recovery measured in months. Those are not abstractions, and the itemized figures are in what the operation actually costs.
• Doing nothing — not neutral. Continued deconditioning, sleep disruption, and the metabolic consequences of reduced movement, all of which have their own mortality.

What we will not claim

We will not tell you PRP is risk-free, that it works for everyone, or that it regrows cartilage. The most common bad outcome is not a complication at all — it is spending money on a treatment that does not help you, which is why the candidacy assessment matters more than the injection technique.

How the preparation itself affects risk

Not all PRP is the same product, and the differences have safety implications that rarely get discussed. Two variables matter most.

Leukocyte content. Leukocyte-rich preparations contain white cells that bring additional inflammatory signaling. In a tendon that may be useful — the aim is to provoke a repair. Inside a joint it is more contentious, because the same signaling acts on synovium and cartilage, and leukocyte-poor preparations are generally preferred intra-articularly for that reason. A clinic using one preparation for every site is choosing convenience over the tissue.

Volume and technique. A large volume forced into a dense load-bearing tendon is a different proposition from a peritendinous placement. This is the mechanism behind most of the rare tendon injuries associated with the procedure, and it is why the Achilles in particular is treated around rather than through in most cases.

Why we do not use corticosteroid as a mixer

Some clinics add a small dose of corticosteroid to reduce the post-injection flare. It does reduce it, and it also directly opposes the mechanism you are paying for — suppressing the inflammatory cascade that the platelets were delivered to provoke. The flare is uncomfortable for three days. Blunting it can cost the treatment its effect.

If the flare is the part you are most worried about, that is a reasonable thing to plan around with timing, work schedule and non-anti-inflammatory analgesia. It is not a reason to undermine the injection.

What people ask about safety

Can I be allergic to it?

No — it is your own blood. That is the main safety advantage. How PRP works.

Should I take antibiotics beforehand?

For PRP, no. For BMAC, yes — different procedure, different risk. PRP compared with BMAC.

Is the flare a sign something went wrong?

No. It is expected and is the mechanism working. Escalation after day three is different. Recovery timeline. What the three days look like in order, and what is not normal.

I take a blood thinner. Can I still have this?

Often yes, with planning. It needs an individual conversation. Candidacy.

Related reading

• PRP for the disc — and why discitis governs it
• PRP compared with BMAC
• PRP compared with cortisone
• Recovery timeline
• Am I a candidate?

What the first three days feel like, site by site.