A young person’s injury that behaves like an old person’s problem.

PRP FOR PATELLAR TENDINOPATHY

Jumper’s knee is a young person’s injury that behaves like an old person’s problem: it persists, it resists rest, and it frequently ends careers in sports that nobody outside them considers dangerous.

Where it hurts and why that is diagnostic

The pain sits at the inferior pole of the patella, at the proximal insertion of the patellar tendon, and it is exquisitely localized — most people can put one fingertip on it. It hurts with jumping, deceleration, decline running and deep knee flexion under load, and characteristically it warms up: the first few minutes of activity hurt, the middle feels acceptable, and the hours afterward are worse.

That warm-up pattern is typical of tendinopathy and distinguishes it from patellofemoral pain, which tends to worsen steadily through activity rather than easing.

The tissue

The deep posterior portion of the proximal tendon degenerates: collagen disarray, increased ground substance, neovascular ingrowth with accompanying nerve fibers. Imaging often shows thickening and hypoechoic change. As elsewhere, it is a failed repair rather than an inflammatory process, which is why prolonged rest disappoints — rest removes the stimulus that tendon needs to rebuild without addressing why it stopped.

Why it stalls in people who are otherwise fit

This is the interesting part, because these patients rarely have the metabolic profile that explains tendinopathy elsewhere. Two biological factors still apply. The proximal deep tendon is a zone of stress concentration and relatively poor perfusion, loaded eccentrically at very high rates during landing. And energy availability matters: athletes in chronic energy deficit, or with disrupted sleep from training and travel schedules, have measurably impaired collagen synthesis. Repair is an anabolic process and it requires substrate and recovery.

The third driver is entirely social and it is the most powerful one: nobody rests a patellar tendon in season. Selection pressure, scholarships, teammates, and the fact that it is playable in the short term all conspire to keep loading a tendon that needed twelve weeks. The condition becomes chronic because stopping is expensive in ways that are not medical.

What PRP contributes here

The mechanism is the standard one, and this is a reasonable indication: a degenerate, poorly perfused tendon with a stalled repair, in a structure where fenestration plus growth-factor delivery has a direct rationale.

The evidence is moderate. Comparisons against dry needling and against exercise alone generally favor PRP, and there is some support for it outperforming corticosteroid over the medium term. As with everything else, the loading program does much of the work, and PRP performs best as an adjunct to it rather than as a substitute.

The loading program is the treatment

More so here than almost anywhere else on this site. Heavy slow resistance training has strong evidence in patellar tendinopathy in its own right, and it is not optional.

• Weeks 0–2 Isometric quadriceps holds — genuinely analgesic in patellar tendinopathy, often within minutes, and they preserve strength while the tendon is irritable.
• Weeks 2–8 Heavy slow resistance: leg press, squat and knee extension at slow tempo with meaningful load. Volume and load, not comfort, drive the adaptation.
• Weeks 8–16 Energy storage work reintroduced — jumping and deceleration — progressively and in that order.
• Return to sport Governed by load tolerance and by symptoms the following day, not by the calendar.

What else it might be

• Patellofemoral pain — diffuse rather than point tender, worsens steadily through activity
• Fat pad impingement — pain behind and either side of the tendon, aggravated by hyperextension
• Osgood–Schlatter or Sinding–Larsen in a skeletally immature patient — apophysis rather than tendon
• Patellar stress fracture — rare, and a reason not to inject

The calendar decides as much as the tendon does

Patellar tendinopathy is the one condition here where timing is a hard gate rather than a preference. The treatment needs roughly twelve weeks of protected, progressively loaded rehabilitation to be worth anything, and an athlete cannot serve that sentence in the middle of a season. Injecting in March so that someone can keep jumping in April produces a tendon that is both treated and still failing.

So the person this suits is in an off-season or has accepted one: pain at the inferior pole of the patella, worse on decline and on landing, present for months, and a proper heavy slow-resistance program already attempted rather than described. That last point matters more here than anywhere else on this site, because loading is genuinely first-line for this tendon and it genuinely works. Someone who has not done it does not need an injection; they need the program.

Two diagnoses are ruled out before anything else. In a growing athlete, pain at the same site is far more often apophysitis — the growth plate, not the tendon — which is managed differently and resolves with skeletal maturity. And a suspected patellar or tibial stress fracture is excluded on imaging first, because loading it as a tendon problem is how a stress reaction becomes a fracture.

Why it fails when it fails

The most common reason is that the loading program was nominal rather than heavy. The second is that the diagnosis was patellofemoral rather than tendon. The third is that training load never actually changed, in which case nothing done to the tendon will hold.

Why load management beats rest, specifically here

The instinct with a painful tendon is to stop. In patellar tendinopathy that instinct is close to exactly wrong, and understanding why changes how people approach the whole rehabilitation.

Tendon is metabolically responsive tissue. Mechanical loading is the signal that drives collagen synthesis and alignment; remove the signal and the tendon does not rest, it detrains. Two weeks of complete rest reduces tendon stiffness and load capacity measurably, so the athlete returns to sport with less tolerance than they had when they stopped, reinjures immediately, and concludes the tendon is fragile.

What actually helps is reducing the energy-storage load — jumping, cutting, decelerating — while increasing slow heavy load. The tendon keeps receiving the signal to rebuild without the high strain rates that provoke it. That distinction, between kinds of load rather than amounts of load, is the single most useful idea in this condition.

The quadriceps and the calf both matter

A patellar tendon is loaded by what the leg above and below it fails to absorb. Quadriceps weakness means the tendon takes strain the muscle should have taken. Restricted ankle dorsiflexion changes landing mechanics and shifts load forward onto the knee. Poor gluteal control lets the knee collapse inward on landing, which loads the tendon asymmetrically.

Treating the tendon without addressing those is why the condition recurs. It is also why the assessment here includes a landing screen rather than only a palpation of the sore spot.

What athletes ask about jumper’s knee

Is this the same as runner’s knee?

No — that is usually patellofemoral pain, which is diffuse rather than point tender. What we treat.

Can I keep playing?

Often physically possible and usually why it became chronic. Recovery timeline.

Why do isometrics help so quickly?

They have a direct analgesic effect on tendon pain, separate from any structural change. What to expect.

Should I have cortisone instead?

Generally not in this tendon — weakening a structure that takes landing loads is a poor trade. The comparison.

Related reading

• PRP for knee osteoarthritis
• Achilles tendinopathy
• Recovery timeline
• Am I a candidate?

A note on who this happens to. Patellar tendinopathy occurs largely in young, athletic, metabolically well people, which makes it the tendon where the systemic argument applies least and the loading argument applies most. That is not true of most conditions on this site, and it is the reason this page is built around load rather than around bloodwork. The contrast is on the tendinopathy page.