Category: Questions patients ask

WHAT IT FEELS LIKE

It is not the needle people remember. It is the two or three days afterward, and how much those days differ depending on what was injected.

Why the soreness happens at all

PRP works by provoking a controlled inflammatory response — that is the mechanism, not a side effect of it. A treatment that produced no reaction would be a treatment that did not signal anything. So post-injection soreness is expected, informative, and the part of the consent that is most often glossed over.

It gets worse before it gets better, and that is the treatment — but knowing that in advance is the difference between a normal week and a frightening one.

By site, honestly

• Tendon, and especially an enthesis. The most uncomfortable of them. Injecting into a tightly bound structure with limited compliance produces real pressure pain during the injection and a pronounced ache for two to four days. Gluteal and patellar tendons are typically the ones people rate highest.
• Plantar fascia. Small volume into dense tissue on a weight-bearing surface. Brief and sharp, then a few days where the first steps are worse than usual before they are better. The first step out of bed is the diagnosis, and it is also the thing that tells you the treatment is working.
• Large joints. Knee and hip are generally the easiest. The capsule accommodates volume, the injection itself is brief, and the ache that follows is a fullness rather than a sharpness. Foot and ankle work sits between the two.
• Spine. Different again, because the discomfort is mostly positional afterward rather than at the site. We do not inject a level until a block has told us it is the one.
• The blood draw. Worth saying because people brace for it and it is the least of the day.

The three days, in order

Day zero is usually the easiest — local anesthetic is still working and people frequently leave feeling better than they expected. Days one and two are the peak, and they are the days to clear the calendar for. By day four most people are back to their baseline discomfort, and the actual benefit begins arriving over the following weeks.

What we ask you not to do in that window is take an anti-inflammatory to blunt it. That is the one instruction people break, and it works directly against the mechanism you have paid for. Acetaminophen, ice, and knowing it is coming are the plan.

What is not normal

Expected soreness is proportionate, local, and improving by day three or four. What is not expected: pain that escalates after day three, fever, spreading redness, or a joint that becomes hot and increasingly swollen. Those are the calls to make rather than wait out. The expected, the uncommon, and the three that warrant a call are listed separately and deliberately short.

Infection after an autologous injection performed under sterile conditions is rare. Rare is not never, which is why the list exists and why we would rather hear from you.

RESPONDERS

Two people get the same injection into the same joint at the same grade, and one improves for a year while the other reports nothing. That difference is not random, and most of it is knowable before the needle.

Three things vary, and only one is the treatment

The first is what was in the syringe. Preparation systems differ in platelet yield by several fold, in leukocyte content by design, and in whether the product is activated. Two clinics can hand you the same word and deliver materially different biology, and the dose that reaches the tissue tracks with outcome. The leukocyte question alone changes the direction of the effect in some tissues.

The second is the target. A joint injected without knowing which structure generates the pain is a coin toss dressed up as a procedure. Facet pain is a diagnosis you make with a needle, not a scan, and a disc that hurts and a disc that looks bad are not the same disc.

The third is you — and this is the one nobody discusses, because it is the least marketable and the most consequential.

The terrain does the healing

PRP does not repair anything. It signals; your cells repair. So the capacity of those cells is the ceiling on the result, and that capacity is measurable.

Type 2 diabetes changes tendon homeostasis directly: collagen cross-linking, matrix turnover and the cellular response to injury are all altered, and orthopedic outcomes across procedures are consistently worse in poorly controlled disease. Insulin resistance short of diabetes moves the same levers more quietly. Add smoking, which impairs the microvascular supply the repair depends on, and chronic sleep restriction, which suppresses the largely nocturnal repair signaling, and you have most of the variance that gets attributed to the injection.

None of that is a lecture about discipline. Access to food, shift work and the cost of both are doing a share of it, and a plan that ignores that is a plan for somebody else. But it is the reason we ask for bloodwork before we quote you a probability. Why a pain clinic asks to see your bloodwork.

What we look at before agreeing to treat

• HbA1c and fasting insulin. Not to disqualify you — to know what we are working with, and to tell you honestly what it does to the odds.
• Vitamin D and thyroid function, both of which affect connective-tissue repair and both of which are correctable.
• What you are taking. Sustained anti-inflammatory use around the treatment window works against the mechanism you are paying for.
• Prior corticosteroid exposure at the site, and how recent. The two are not interchangeable and the sequence matters.
• What the tissue actually is. A cuff tear with fatty infiltration and a tendinopathy are different problems. The tear is only half the diagnosis.

The uncomfortable version

I spent years attributing variable results to the preparation, because that is the part a physician controls and the part that is interesting. It is real, and it is not the largest term. The largest term is the metabolic state of the person on the table, and I was not measuring it.

Which means the most useful thing you can do before a regenerative treatment is not choosing a clinic with a better centrifuge. It is arriving with the terrain in better shape than it is now, and there is usually more room there than anyone has told you.

HOW LONG

The question people mean is not how long the platelets survive. It is how long the change they produced holds — and those are different clocks with different answers.

The platelets are gone in days

Injected platelets degranulate within hours and are cleared within days. If PRP worked by the platelets staying put, the effect would end that week. It does not, which tells you the mechanism is not the platelets themselves but what they signal — a shift in the local environment toward repair, changes in synovial behavior, and recruitment of the cells that actually do the work.

That is why the effect takes weeks to arrive and why it often gets worse before it gets better. You are not waiting for a drug to take effect. You are waiting for tissue to respond.

What the comparative trials show

The most informative comparison is against corticosteroid, because the shapes of the two curves differ rather than just the heights. Steroid works faster and fades; PRP is slower to arrive and tends to still be doing something at six and twelve months. Meta-analyses comparing PRP with hyaluronic acid in knee osteoarthritis point the same way — the separation between the two widens at the later time points rather than the early ones.

So a reasonable expectation for an appropriately selected knee is improvement measured in months rather than weeks, commonly still present at a year, and not permanent. One of these works faster and the other tends to still be working.

Why “how long” is the wrong frame for a tendon

In a joint, PRP modifies an environment that continues to be loaded, so the effect decays as the joint keeps doing what it was doing. In a tendon the goal is different: you are trying to convert a failed healing response into a completed one. When that works, the question of duration partly dissolves — a tendon that has remodeled is not on a countdown.

When it does not work, repeating the injection without changing the load that caused it is the common error. The tendon is not inflamed, and the loading pattern is doing more than the syringe.

What shortens it

• Continuing the load that caused it, unchanged. The most common reason a good result does not hold.
• Advanced structural disease. A joint with very little cartilage left has less to work with, and honesty about that is part of the consent. A replacement is a very good operation, and timing it is your decision.
• Metabolic terrain. Insulin resistance and poor glycemic control measurably impair tendon and connective-tissue healing. This is the variable most often left out and the one most open to change. It is why we look at your bloodwork.

And one thing that does not shorten it: having had the injection before. Repeat treatment is a clinical decision based on what happened, not a diminishing-returns rule.

HOW MANY

There is no magic in a series of three. The number is a clinical decision made from your tissue and your response, and anyone quoting you a course before they have examined you is selling a package rather than planning treatment.

Where the number three came from

Largely from convention and from how clinics schedule, not from a trial that tested three against two. It became the default answer because it is a tidy thing to say and an easy thing to book.

What the evidence does support is narrower and more useful: in knee osteoarthritis, comparative work has found multiple injections outperforming a single one, and a separate line of research finds that the total platelet dose delivered correlates with outcome. Those are two different claims. The first is about repetition; the second is about how much you actually got. A clinic using a low-yield preparation may need three to reach what another delivers in one.

Which is why the question “how many” cannot be answered without knowing what is in the syringe. Two syringes labeled PRP can behave in opposite directions, and that is most of why the trials disagree.

What actually decides it

• The tissue. A tendon and a joint do not behave the same way. Tendon remodeling runs over months and is more likely to justify a second treatment; an intra-articular knee injection is judged differently. Each tissue has its own clock.
• What the first one did. This is the honest driver. A meaningful partial response at six to eight weeks is the best argument for a second. No response at all is an argument for re-examining the diagnosis, not for repeating the injection.
• The stage of the joint. The knee is where this treatment has the most to stand on, and the earlier grades respond better than the late ones.
• Your terrain. The biology doing the repair is yours. Why a pain clinic asks to see your bloodwork is not a digression here — it is the variable most likely to be limiting the result.

Our position, stated plainly

We do not pre-book a course. Intervals are scheduling facts; quantities are clinical decisions, and the decision is made after we see what the tissue did. If you are told at the first visit that you need exactly three, ask what would change that number. A good answer exists. If none is offered, the number was not clinical.

The corollary is the part people like less: sometimes the honest answer after one injection is that this is not the right treatment for your problem, and a second will not fix that. Being told you are not a candidate is the point of asking.

What the consensus documents say

Expert consensus and guideline groups have converged on PRP being a reasonable option in knee osteoarthritis while being explicit that preparation and protocol heterogeneity limits how precisely anyone can specify a regimen. That is an honest position and it is the one we hold: the evidence supports the treatment more confidently than it specifies the schedule.

It is worth separating two things that get conflated. PRP is not covered by most payers — that is a budgeting decision. It is a different statement from anything about the strength of the evidence, and not covered is not the same as unproven.