Jumper’s Knee: Why Rest and Injections Fail, and Load Wins

Transcript

Sam: Here's a sentence that should not be true. In a proper trial for one of the most common knee injuries in sport, they tested the fancy regenerative injection athletes swear by against a shot of plain salt water. The salt water won.

Alex: Not tied. Won. And it's not a fluke — it's the whole story of this injury in one result. The thing that feels like the cure is usually the trap, and the thing that actually works is the one nobody wants to hear.

Sam: Welcome back to Dan's Rabbit Holes.

Alex: The show that takes one thing genuinely worth getting to the bottom of and follows it all the way down — past the headline, past the received wisdom, to what's actually going on. Whatever's caught the light and deserves a proper look.

Sam: I'm Sam, here with Alex, and today we are going down the hole on jumper's knee. The medical name is patellar tendinopathy — that ache right at the bottom of the kneecap that stalks anyone who jumps for a living. Volleyballers, basketballers.

Alex: And it is the perfect rabbit hole, because almost everything the average person gets told about it is wrong. You get told it's inflamed, so rest it, ice it, maybe get a cortisone shot. We're going to pull that apart and show you that the tendon usually isn't inflamed at all — it's doing something much stranger.

Sam: And that one fact flips the entire treatment plan upside down. It's the difference between "put out a fire" and "rebuild a bridge." So here's the map. Why the obvious fixes fail, why the expensive fixes fail even harder — that salt water result — and then the small list of things that genuinely help.

Alex: There's a real edge at the frontier. It's just much quieter, and much less glamorous, than the marketing. If you've had this, or you've watched someone limp through it for a year, this is the episode.

Sam: If you're enjoying the show, take one second and hit follow in whatever app you're in — it's free, and it's genuinely the biggest thing that helps a small show like this keep going. Okay. Let's start with the lie in the name.

Alex: So the name people use is "patellar tendinitis." And "-itis," on the end of any medical word, means inflammation. Appendicitis, bronchitis — inflamed appendix, inflamed airways. Tendinitis: inflamed tendon.

Sam: Right, that's the whole mental model baked into the word.

Alex: It is. And here's the problem. When researchers actually take a chronically painful patellar tendon and biopsy it — look at the tissue under a microscope — most of the time they do not find inflammation. They don't find that hot, swollen, immune-cell-rich tissue you'd expect from a fire.

Sam: So what do they find instead? If it's not inflamed, what's it doing?

Alex: The opposite, almost. Think of a healthy tendon as a rope — thousands of collagen fibres, all combed in the same direction, tightly bundled, incredibly strong along that line. In a bad tendon, that rope has come unwoven. The fibres are frayed and disorganised. There's this watery, gel-like substance building up where strong fibre should be. And the really strange part — new blood vessels and new nerve endings have grown into it.

Sam: Wait, why is that strange? Blood vessels sound like healing.

Alex: Because a healthy tendon is almost bloodless. It's meant to be. And those new nerve fibres growing in alongside the vessels? A lot of researchers think that's a big part of why it hurts so much. The tissue isn't screaming with inflammation. It has quietly stopped keeping up with its own maintenance.

Sam: Okay, so give me the framework. Is there a name for this idea?

Alex: There is, and it's the spine of the whole modern understanding. Two researchers, Jill Cook and Craig Purdam, published what's called the continuum model back in 2009. And the idea is that a tendon moves along a line depending on how it's loaded. Overload it once or twice, and it goes into a short "reactive" phase — it thickens up to cope, and that genuinely can settle with a bit of rest.

Sam: So a little bit of trouble it can bounce back from.

Alex: Exactly. But overload it again and again — the way a volleyballer's knee gets hammered every single session — and it slides past that. Into "disrepair," and then "degeneration." That's the frayed rope, the gel, the vessels growing in. And crucially, that stage does not just settle with rest.

Sam: And this is where I can see why every instinct we have is wrong. Because if it's degeneration, not inflammation — resting it is doing nothing to the actual problem.

Alex: Worse than nothing. A tendon adapts to the load you put through it. Rest a healing-failed tendon and you drop the load even further below what it needs to rebuild. So it gets weaker. And then the moment you go back to sport, the pain's right there waiting, because you never fixed the thing — you just detrained it.

Sam: And the anti-inflammatories?

Alex: Aiming at a target that's largely not there. You're taking a drug to put out a fire in a building that isn't burning. It might mute some pain around the edges, but it's not touching the failed structure underneath.

Sam: So the entire job flips. It's not "calm this down." It's —

Alex: It's "coax a lazy, under-built structure into rebuilding itself." That is the whole game. And once you've got that in your head, every single decision downstream changes.

Sam: So before we get to the fixing — because I really want to get to how you actually rebuild the thing — I want to understand who gets this, and why it hits jumpers so hard specifically.

Alex: Yeah, and there's a lovely dark logic to it. If you sat down and tried to design a sport to manufacture this injury, you would basically invent volleyball.

Sam: Why volleyball over, I don't know, running or football?

Alex: Because of what the patellar tendon actually does. It's not just a strap holding your kneecap on. It's a spring. An energy-storage spring. Every time you land from a jump, that tendon stretches to absorb your entire body's momentum coming down — and then it recoils, and fires you back up into the next jump.

Sam: Oh. So it's loading up like a bow and firing like an arrow, over and over.

Alex: That's exactly it. Stretch, store, release. And that specific pattern — the stretch-shorten cycle — is the single hardest thing you can ask a tendon to tolerate. And volleyball asks for it hundreds of times a session.

Sam: So how common does that make it? Give me the number.

Alex: In elite volleyball, roughly forty-five percent of players are carrying patellar tendinopathy. Forty-five.

Sam: Nearly half the pro court has this.

Alex: Nearly half. And here's the comparison that tells you what's really going on. In recreational players — same sport, same movements, just less of it — it's around fourteen percent. So the elite rate is more than three times the weekend rate.

Sam: And the thing that separates those two groups is basically just volume, right? How much they jump.

Alex: That's the punchline, and it matters enormously. It's not that the pros have unlucky genetics or weird knees. The biggest driver, by a distance, is jump volume — and especially sharp spikes in training load, when someone suddenly ramps up. Being taller, heavier, male nudges the risk too. But it tracks the dose of jumping almost directly.

Sam: Okay, I have to ask about sand, because this whole thing started with beach volleyball. Sand's soft. Isn't landing in sand gentler on the knee?

Alex: You'd think so, and it's a genuine double-edged sword. Sand cushions the landing — it lowers that peak impact, which is good. But sand is also unstable and it's springless. It gives nothing back. So the athlete has to work much harder on every jump, and can end up putting more total load through the tendon, not less.

Sam: So "soft surface" doesn't equal "safe."

Alex: Right, and that's the deep lesson hiding in it. The tendon doesn't care how the load is delivered — hard court, soft sand, gym. It only ever responds to the total dose. Which sets up the brutal bit for anyone already hurting.

Sam: Which is what?

Alex: You cannot out-treat a load you keep re-applying. If you're asking that tendon to store and release energy at full spike intensity every session while it's trying to remodel — it will stay stuck. It doesn't matter what else you throw at it.

Sam: Okay. So we've established the tendon isn't on fire — it's a repair job that stalled. And we've established that the jumping is what stalled it. So logically, the fix has to be about how you load it. This is the part I actually want.

Alex: And here's the good news and the bad news in one breath. The single best-proven treatment for jumper's knee is loading. Strengthening it. And loading is exactly the thing most motivated people will tell you they've already tried, and it didn't work for them.

Sam: Which sounds like a contradiction. If load is the cure, why do so many people load it and stay broken?

Alex: Because when a proper loading programme fails, the method is almost never the problem. The dose is. And this is actually the same lever we pulled apart in our weight-training episode — number nine, a couple of months back. Mechanical load is a signal. It's a message that tells living tissue: build. But the signal has to be strong enough, specific enough, and repeated for long enough to actually be heard.

Sam: So people are whispering to the tendon when they need to be shouting.

Alex: Right — and often literally that quiet. Let me give you the concrete version, because even the "right" exercise has moved on. For years the gold standard was something called Alfredson eccentric decline squats — you stand on a slanted board and slowly, painfully lower yourself on one leg. Just the lowering phase.

Sam: I can feel that being horrible.

Alex: It is horrible, and that's part of the problem — it helps some people, but chronic cases often respond poorly, and it's unpleasant enough that loads of people quietly quit. The stronger evidence now is behind something called heavy slow resistance. HSR.

Sam: Which is what — what's different about it?

Alex: You use both phases, up and down, not just the lowering. Heavy weight. Deliberately slow tempo. A few times a week. And in head-to-head trials it matches or beats the old eccentric-only approach, people actually stick with it, and — this is the key — it drives real tissue change. You see increased collagen turnover in the tendon. It's not just masking the symptom; the rope is being rebuilt.

Sam: What about the isometric thing? I feel like I've heard that holding a position kills tendon pain, almost like a switch.

Alex: You've heard right that it got hyped that way, and here's the honest version. Isometrics — long holds against something that won't move — are a genuinely useful tool. Good way to load a tendon that's too angry for heavy lifting. But there was a striking finding back in 2015 that they had this special, reliable painkilling effect —

Sam: And let me guess. It didn't hold up.

Alex: It didn't. Multiple later studies just failed to reproduce it. So isometrics are a good tool. They are not a magic pain switch. And that pattern — an exciting early result that quietly fails to replicate — you're going to hear it again in this episode.

Sam: Okay, so if the exercise choice isn't really the issue, what's the actual question someone should be asking?

Alex: The question isn't "which exercise." It's "am I dosing this properly?" And modern loading is staged. You climb a ladder — calm the tendon, rebuild heavy strength, reintroduce spring and jumping, then back to sport. And you earn each rung by proving the tendon tolerated the last one.

Sam: How do you prove that? How do you know you didn't overcook it?

Alex: There's a lovely simple rule for it. If your pain has settled back to its normal baseline within twenty-four hours of a session, the load was acceptable. If you're still lit up two days later, you went too hard. That's your dial.

Sam: That's really usable. So why do so many people still stall on that ladder?

Alex: Three quiet saboteurs, and they get almost everyone. The first is compression. If you load the tendon in a really deep knee bend — deep squats, lunges all the way to the floor — you actually pinch it against the bone underneath, and that can flare it, especially early on. So you load in moderate ranges first, add depth later.

Sam: Second?

Alex: The kinetic chain. Your patellar tendon is the last link in a chain that runs up through the calf, the ankle, the hip. If your ankles are stiff and your calves are weak and your hip won't absorb load, all that extra work gets dumped down onto the knee. If you only ever rehab the sore spot, you leave the real cause sitting upstream, untouched.

Sam: And the third one I think I can already guess, given everything you've said about time.

Alex: Go on.

Sam: It's just... time. And impatience. You're not giving it long enough.

Alex: That's the big one. Tendons remodel over months. Three to six at the very least, sometimes a full year. And every full-intensity spiking session you sneak in during that window resets the clock. So when someone says "loading didn't work for me," the honest checklist is: was it heavy and slow enough, was it out of that deep compression, were you training the calf and the hip — and did you give it uninterrupted months without piling competitive jumping on top.

Sam: And I'm betting for most people, the answer to at least one of those is no.

Alex: For most people it's no to three of them.

Sam: So let's talk about what people reach for when their patience runs out. Because months is a long time to be in pain, and I know exactly where a lot of people go next. The needle.

Alex: The needle. And the first one, the classic, is the cortisone shot. A corticosteroid injection. And I want to be careful here, because this one is a genuine trap — it's a trap precisely because it works, at first.

Sam: Set up the trial for me. How do we actually know?

Alex: There's a really clean one, out of Denmark, in 2009 — Kongsgaard and colleagues. They took patients and split them three ways: cortisone injection, the eccentric squat training, or that heavy slow resistance we talked about. And they used a standard score for tendon function and pain — higher is better.

Sam: Okay, so three arms. Drug versus two kinds of exercise.

Alex: Right. At twelve weeks, the cortisone group looks like the runaway winner. Their function score jumps from 64 up to 82. Their pain during sport drops from 58 down to 18 — on a hundred-point scale. That is a massive improvement. It genuinely feels like a cure.

Sam: So at that point, if you're the patient, you're telling everyone cortisone is a miracle.

Alex: You're evangelising. And then the six-month follow-up comes in. And the cortisone group's function score has fallen all the way back down to 64.

Sam: Wait — 64? That's exactly where they started.

Alex: Exactly where they started. Round trip. And the pain had crept back up with it. Meanwhile the two exercise groups, who had a much less dramatic start, held their gains at six months.

Sam: So the injection didn't heal anything. It just... borrowed some good weeks.

Alex: It borrows the comfort and it charges interest. Six months in, they're back to square one — and the two exercise groups, who started off far less impressive, have quietly kept their gains and sailed past. And there's a second reason to be wary, which is almost worse. Corticosteroid actually weakens tendon tissue.

Sam: Oh, that's bad. This is the one tissue whose whole job is to be strong.

Alex: Its entire job is to transmit big forces. And if you inject a drug that softens it, purely to mask the pain, you're carrying a real — uncommon, but real — risk of the thing rupturing. So you're deliberately weakening the one structure you need to hold. Cortisone has a narrow, legitimate use — buying a short window to get a totally stuck, too-painful-to-move tendon moving again. But as a standalone fix, it reliably makes people worse over the timeline that actually matters.

Sam: Okay but cortisone's the old one, right? The one everyone knows is a bit dodgy now. What about the modern injection — the one that sounds like the future?

Alex: This is where we come back to the salt water. Platelet-rich plasma. PRP. And this is sold as regenerative medicine — it's everywhere in elite sport, you've seen the photos of famous athletes getting it.

Sam: Talk me through what it even is, because "platelet-rich plasma" sounds impressive and I don't actually know what's in the syringe.

Alex: So they take your own blood, they spin it down in a centrifuge to concentrate the platelets and the growth factors in it, and then they inject that concentrate back into your bad tendon. And the pitch is: these are your body's own healing signals, delivered right to the injury. It sounds fantastic.

Sam: It sounds like exactly what you'd want for a tendon that's failed to heal. Deliver the healing signal straight to the spot.

Alex: It sounds perfect. So here's the trial. A really rigorously designed one. They took chronic patellar tendinopathy patients and split them three ways: one group got PRP that's rich in white blood cells, one group got PRP that's poor in them, and the third group got a saline injection. Salt water. And every single one of them was also doing the same exercise programme underneath.

Sam: Which is the fair way to test it — everyone loads, and you're asking what the injection adds on top.

Alex: Exactly right. So, a year later. The function scores. The rich PRP group: 58. The poor PRP group: 71. And the salt water group —

Sam: Don't tell me.

Alex: Eighty. The saltwater placebo group scored the highest of the three. And the differences weren't even statistically significant — so honestly you shouldn't read too much into salt water "winning" — but that's the point. A single PRP injection did no better than injecting nothing but salt water.

Sam: That is genuinely wild. So all that growth-factor, regenerative-medicine story —

Alex: The story sells beautifully. The biology just didn't cooperate. And when you pool it across all the trials, it's the same — PRP shows no reliable advantage over the other options, and there's no good proof it beats plain exercise. It's probably an expensive placebo.

Sam: Okay, so is every needle useless then? Or is there one that isn't nonsense?

Alex: There's one concept that's actually defensible, and it's clever, because it uses the degeneration model directly. It's called a high-volume image-guided injection. Remember those new blood vessels and nerves that grew into the tendon — the ones we think are driving the pain?

Sam: The ingrowth. Yeah.

Alex: This injects a large volume of fluid — mostly saline — under ultrasound guidance, to physically strip those vessels and nerves away. Mechanically shear them off. And the case series are promising: function scores climbing from the low 40s up into the high 70s over the following year.

Sam: That sounds much better than the PRP numbers. So why the caution in your voice?

Alex: Because those studies are uncontrolled. There's no comparison group. And every one of those patients was also doing their loading. So some of that improvement is just... the exercise doing its job. It's a reasonable add-on for a genuinely stubborn case that's already doing the strength work. It is not a substitute for it.

Sam: So the whole injection tier, if you had to rank it honestly?

Alex: Honestly? None of it replaces load. Cortisone is actively counterproductive over time. PRP is probably a costly placebo. And the vessel-stripping stuff is a reasonable extra for stubborn cases who are already doing the real work. The glamour of the injection is almost perfectly inverted against how well it works.

Sam: So that's the stuff that fails, or backfires. But you promised me there's a real edge somewhere. Stuff that genuinely helps. So let's flip to the good news — what does a sharp clinician actually reach for once the loading basics are truly in place?

Alex: And that "once the loading is in place" is the whole frame for this section. Everything I'm about to name is an amplifier bolted on top of the strength work. Not one of them is an engine that runs without it. With that said — there's a handful, each with a real mechanism and modest evidence.

Sam: Give me the list. Start with the one that sounds most like a gadget.

Alex: That'd be shockwave. Extracorporeal shockwave therapy — they fire acoustic pulses, sound waves, straight at the tendon. The idea is it disrupts those abnormal vessels and nerves and kicks off a repair response. The evidence is genuinely mixed — it's not clearly better than a sham treatment for short-term pain — but for chronic, stubborn cases, some reviews put it roughly on par with surgery over the long run. And it's low risk. So, worth a go when you're stuck.

Sam: Okay, next.

Alex: This one's my favourite for the sheer surprise of it. Glyceryl trinitrate patches. Which is nitroglycerin — the exact stuff people take for heart pain, angina.

Sam: Hang on, the heart medication? On your knee?

Alex: On your knee. You stick the patch over the tendon, and it delivers nitric oxide through the skin, and that appears to stimulate the cells that actually make collagen. Some of the analyses rank a nitric-oxide patch plus loading among the more promising combinations out there. The catch is the trial quality is low, and a very common side effect is headaches — because, you know, it's a blood-vessel drug.

Sam: Of course it is. Okay, what's the most elegant one on the list — you hinted there was a clever one.

Alex: Gelatin. Or collagen, with vitamin C, taken about an hour before you load. And the reason it's elegant is the timing. Vitamin C is a required ingredient for building collagen — you can't make the stuff properly without it. And it turns out that if you take a dose of gelatin in that narrow window when exercise has increased blood flow to the tendon, you roughly double a marker of collagen synthesis.

Sam: So you're flooding the raw materials in at the exact moment the tendon's door is open.

Alex: That's exactly the mechanism. You water the plant right when the roots are drinking. And the follow-up work, pairing that with heavy slow resistance, got better symptom outcomes than the loading alone. Small, but real, and basically free and harmless.

Sam: I love that one. What else?

Alex: Two more. One's this fascinating idea called neuroplastic loading. It comes from the discovery that in tendinopathy, the brain's control of the quadriceps muscle is measurably altered — the muscle fires erratically, the wiring's gone a bit haywire.

Sam: So it's not just the tendon that's the problem, it's the control system driving the muscle above it.

Alex: Right, and so the fix is oddly simple: you do your strength work to a metronome. An external beat. Matching your reps to a pace outside your own head appears to re-normalise that control and cut the muscle inhibition. And the last one is blood-flow-restriction training — you lift light weights with a cuff on the leg that partially cuts off the blood flow, and it can drive strength gains comparable to lifting heavy. Which is genuinely useful when the tendon is still too irritable to load heavy directly.

Sam: So if I zoom out on that whole list — shockwave, the heart patch, the gelatin, the metronome, the cuff — is there a single one of them that's a green light across the board? A clear winner?

Alex: No. And that's the entire point of the frontier. Nothing on it is a miracle, and nothing on it works without the loading underneath. They are amplifiers, not engines. Every single one buys you a little on top of the work.

Sam: Okay, so before we land this — there are always two things people ask about that we haven't touched. The really futuristic option, and the surgeon. Where do those sit?

Alex: Right, the two ends of the drama. Let's take the futuristic one first: stem cells. Usually mesenchymal cells taken from your own bone marrow, injected into the tendon. And this is the one place I get to say something genuinely hopeful — the early trials are actually encouraging.

Sam: Oh, interesting. So this one might be real?

Alex: Might be. In chronic cases where there's an actual structural gap in the tendon, the cells were linked to better tissue regeneration than PRP, and better pain and function out to a year. But — and it's a big but — this is a handful of small, early studies. It's expensive, it's not standard care, and you should file it under "promising and unproven," not "the answer." It's a frontier, not a destination.

Sam: Fair. And surgery? The classic last resort — just cut the bad tissue out.

Alex: This is the one that really lands the whole thesis. There's a trial that compared open surgery directly against the eccentric exercise training. Head to head. And both groups improved by basically identical amounts. Surgery offered no advantage over doing the exercises.

Sam: You're kidding. So people went under the knife to get the same result they'd have got in the gym.

Alex: Same result. And here's the kicker inside it — some of the exercise patients who "failed" and went on to have the operation might simply have needed more time on the programme. A scalpel is a pretty poor substitute for a rehab you didn't finish.

Sam: Which brings it all back to time, doesn't it. That keeps being the villain.

Alex: It's the hardest pill in the whole thing. This injury is measured in months, sometimes years. The people in these trials had typically been in pain for a year or more before they even enrolled. And that slowness isn't a sign the treatment's failing — it is just the biology. Collagen remodelling is glacial. There's no cheating it.

Sam: And the single most common reason it drags on for years is —

Alex: — is that the tendon never actually gets the one thing it needs. An uninterrupted, progressively harder loading stimulus, out of that deep compression, with the calf and hip carrying their share, and without full-intensity jumping stacked on top every few days. That's it. That's the whole recipe, and almost nobody runs it cleanly.

Sam: Okay. Land it for me. If someone's listening to this with a sore knee right now, what are the two or three things they actually walk away with?

Alex: One: stop treating it as an inflammation. It's not a fire. It's a tendon that has failed to heal, and the treatment is to rebuild it — with progressive load, heavy and slow, out of deep compression, training the whole leg chain, over three to twelve patient months, without competitive jumping piled on in the middle.

Sam: Two: don't be seduced by the needle.

Alex: Rank the shortcuts honestly. Cortisone borrows six weeks and charges you the rest of the year. PRP is probably a costly placebo — beaten by salt water. Surgery matches a home exercise programme and no more. The flashier and more expensive it sounds, the less likely it is to actually work.

Sam: And three: the frontier is real, but read the fine print.

Alex: The real edge — shockwave, the nitric-oxide patch, the gelatin timing, the metronome loading, the blood-flow cuff, and one day maybe the stem cells — every one of those is worth exploring. But every one of them is an amplifier bolted onto the loading. Never a replacement for it.

Sam: So the cure was never going to be the exciting thing.

Alex: The cure was never going to be a needle. It was always going to be the work — done properly, in the right positions, for longer than feels reasonable. That's the rabbit hole. It looks like a search for a shortcut, and it ends at "there isn't one, and that's okay, because the real thing works."

Sam: That's a genuinely satisfying place to end up. Thanks for coming down this one with me — and thank you, all of you, for listening the whole way.

Alex: One honest note on how this is made. This show's AI-generated. Some questions are just worth getting to the bottom of, so Dan built a custom stack of AI tools to research, analyse, verify and illustrate them — mostly to learn them himself, and he shares what he finds. AI-assisted, fact-checked, worth a second look.

Sam: And on this one specifically — this is general education, not medical advice. Before you start, change, or stop any treatment for your own knee, see your doctor, a sports physician, or a physiotherapist. Your tendon is yours; get eyes on it.

Alex: Before you go, one genuinely useful thing you can do: follow the show. Whatever app you're listening in right now, there's a follow or a plus button — one tap, it's free, and it does two things. You'll get each new rabbit hole the moment it drops, and honestly, for a small independent show like this one, a follow is the single biggest lever there is for helping it reach other people who love getting to the bottom of things.

Sam: And one quick ask before we wrap — this is the part that actually shapes the show. If there's something in here you'd push back on, or a thread you want us to pull harder on next time, tell us. The address is podcast at connectiveshift dot com. We read every single message, and it genuinely decides what we go down next.

Alex: Until the next one — keep asking the good questions.