Your Knee Was Fine on Monday. The Grading Scale Will Still Be Used Against You.

The knee hits the dashboard. Six weeks later the MRI report comes back and somewhere in it are the words degenerative changes, and an adjuster with a highlighter has everything they need.

The argument writes itself: this knee was already arthritic, the collision merely revealed it, and the claim is worth a fraction of what was asked. It is a good argument against a patient who does not know how joints actually fail.

The injury does not reveal the arthritis. It starts it.

Post-traumatic osteoarthritis is its own diagnosis, and it is common. Roughly half of people who tear an anterior cruciate ligament develop osteoarthritis in that knee, and reconstruction does not reliably prevent it — reviews of the literature have not found convincing evidence that surgical reconstruction lowers the incidence compared with conservative management.

Read that in the direction time actually runs. A joint injured today carries a materially elevated risk of arthritis for decades, which makes a knee injury a question about the next thirty years, not about the next appointment. The defense wants a conversation about what your cartilage looked like last month. The medicine is a conversation about what it will look like in 2046. How exacerbation of a pre-existing condition is actually proven, and why the eggshell doctrine exists at all.

Where PRP sits on the grading scale

Knees are graded Kellgren-Lawrence 0 through 4, from no visible change to bone-on-bone. The 2024 ESSKA-ICRS consensus rated 216 scenarios crossing that grade with age, compartment, effusion and what had already been tried. Its conclusion: intra-articular PRP is appropriate in patients aged 80 or under with grade 0 to 3 arthritis, after conservative or injective treatment has failed. Not as a first move.

The companion ESSKA-ORBIT consensus put three statements at grade A, its highest tier: that the preclinical and clinical evidence supports PRP use in knee osteoarthritis; that effectiveness is shown in mild to moderate disease at grade 3 or below; and that PRP provides a longer-lasting effect than corticosteroid with a safer profile. The 2026 AAPM&R guidance statement added five evidence-based recommendations and eleven best practices on how to select patients and administer it responsibly.

What the head-to-head trials found

Against hyaluronic acid, a meta-analysis of 18 level-1 studies — 811 patients on PRP, 797 on hyaluronic acid — found mean WOMAC improvement of 44.7% against 12.6%. In the same analysis, leukocyte-poor preparations produced better subjective knee scores than leukocyte-rich ones, which is a finding about how the product is made rather than about what it is called.

Against corticosteroid, a 2024 network meta-analysis found PRP, bone marrow concentrate and hyaluronic acid all outperforming steroid on pain and function at a minimum of six months. And a 2025 meta-analysis of randomized trials found the improvement clinically significant, with the size of the effect influenced by the platelet concentration actually delivered.

That last point is not a footnote. It is why two clinics injecting “PRP” can produce two different results and both be telling the truth about what they used. What has to be recorded for the injection to be describable.

Grade 4, where the consensus stops and the decision becomes yours

The ESSKA-ICRS panel did not extend its appropriateness rating to grade 4 knees. Read the underlying numbers rather than the headline: across the whole exercise, 4.2% of scenarios were rated inappropriate and 56.9% uncertain, and grade 4 fell overwhelmingly into uncertain rather than into inappropriate. Uncertain is a statement about the evidence, not a prohibition.

The trial evidence at that grade exists and is worth stating precisely. A prospective, blinded, placebo-controlled study of serial PRP in Kellgren-Lawrence grade 4 knees — in patients unwilling to have joint replacement or carrying relative contraindications to it — reached clinically meaningful improvement in WOMAC and pain scores at three and six months, where saline did not. A four-year follow-up of bone marrow aspirate concentrate in 37 grade 3 and 4 knees reported improvement in 35, with no prosthesis implanted over the follow-up period. These are small studies. They are also the studies that exist for exactly the patient the consensus panel could not rate.

The position here is plain. At bone-on-bone, structure is not going to be restored, and joint replacement remains the definitive operation for the structure and for the person who wants it. But most grade 4 patients are not choosing between an injection and a replacement. They are choosing between an injection and another year of climbing analgesic doses. Time and a lower medication burden are legitimate clinical goals, and they are the goals worth naming out loud at that stage. What escalating medication does to the claim as well as the body.

The meniscus, where the answer is no

A torn meniscus is one of the most common findings after a twisting knee injury, and it is where the honest answer runs against the treatment. The 2019 ESSKA meniscus consensus reviewed biological enhancement — needling, PRP — and found no evidence that it improves healing of a repaired meniscus. What that consensus does say, emphatically, is that preservation beats removal: long-term outcomes after partial meniscectomy are worse than after repair, and many tears once called irreparable should be repaired.

So the meniscus conversation is about preserving tissue, not about injecting it. A page that claimed otherwise would be selling you something.

What has to be in the chart for a crash knee

The mechanism, in detail, recorded early. Baseline imaging read against the examination rather than in isolation, because a radiology report describing degenerative change says nothing about when that change started or whether it hurt last month. Functional measurement at intervals. And where a biologic is used, the indication mapped explicitly to the guideline scenario it belongs to, with the preparation characterized.

One more, and it is the one people skip: the metabolic background. Cartilage and synovium are not inert tissue waiting patiently; they behave differently in a systemically inflamed body, and the injectate is manufactured from that same body. Why the terrain is measured first.

Frequently asked questions

The insurance company says my knee arthritis is pre-existing. Is that the end of it?

No. Post-traumatic osteoarthritis is a recognized consequence of joint injury — roughly half of people who tear an ACL develop arthritis in that knee, and reconstruction has not been shown to reliably prevent it. The clinical question is what the injury started, not only what an image shows today. Learn more: proving exacerbation of a pre-existing condition.

What grade of knee arthritis is PRP appropriate for?

The 2024 ESSKA-ICRS consensus rated it appropriate in patients aged 80 or under with Kellgren-Lawrence grade 0 to 3 arthritis, after conservative or injective treatment has failed, and did not endorse it as a first-line treatment. Grade 4 was rated uncertain rather than inappropriate. Learn more: the full guideline record.

Is PRP better than a cortisone shot for an injured knee?

The ESSKA-ORBIT consensus rated it a grade A statement that PRP provides a longer effect than the short-lived effect of corticosteroid with a safer profile, and a 2024 network meta-analysis found PRP, bone marrow concentrate and hyaluronic acid all outperforming steroid at a minimum of six months. Individual results vary. Learn more: how targeted injections fit between conservative care and surgery.

Will PRP heal my torn meniscus?

The evidence does not support that claim. The 2019 ESSKA meniscus consensus found no evidence that biological enhancement improves healing of a repaired meniscus, and it emphasizes preserving meniscal tissue rather than removing it. Learn more: why preserving structure changes long-term outcomes.

Does bone-on-bone arthritis rule out an injection?

No. Structure will not be restored at that stage, and joint replacement remains the definitive operation for the structure. But a placebo-controlled trial in grade 4 knees found clinically meaningful improvement with serial PRP at three and six months where saline did not, and for many patients the real alternative is another year of rising medication doses. Learn more: what medication escalation costs, medically and legally.

How soon after a crash should a knee be evaluated?

Early, and in detail. The mechanism, the examination and baseline imaging recorded close to the event are what later separate an injury from an alleged pre-existing condition, and early findings also shape treatment. Learn more: what the first days after an injury predict.

Where is Injury Experts located?

Injury Experts is at 4477 Woodson Rd, Suite 202, St. Louis, MO 63134, next to Lambert International Airport, serving the St. Louis region in Missouri and Illinois. Call (314) 887-5866 or text (314) 886-5902.

Medically reviewed by Dr. Gurpreet Singh Padda, MD, MBA, MHP — Board Certified in Anesthesiology, Pain Medicine, Interventional Pain Management, Addiction Medicine, and Obesity Medicine.

This article is for general education and is not medical advice. It does not create a physician–patient relationship. Do not start, stop, or change any medication — including opioid medication — without consulting your physician.