“It Was Going So Well… Then Everything Fell Apart”

Why flare-ups happen during rehab — and why they’re often not a bad sign

Last week in clinic, I saw a patient who perfectly captured a fear I hear all the time.

She’s been rehabbing a knee with a fully torn ACL (one of the main ligaments in the knee), managed conservatively (meaning no surgery). We’ve been working together for months. Her strength had improved. Her confidence had improved. Her stability had improved. Functionally, she was doing really well — teaching fitness classes, staying active, moving more freely.

And then, out of the blue, she walked in and said something like:

“I don’t trust my knee at all. It feels like it’s going to give way. I feel unstable just walking around.”

No fall.
No twist.
No dramatic injury.

Just a sudden sense that everything had unravelled.

If you’re reading this and thinking “That’s exactly what happened to me — just with my back / shoulder / hip / ankle”, keep reading.

Because this pattern is far more common — and far less alarming — than most people realise.

The ACL example: what was actually happening?

On assessment, a few things stood out:

• The knee still moved fully

• There was no locking, catching, or sharp joint pain

• Strength loss was global, especially through the quadriceps

• Muscle activation was inconsistent and “fluttery”

• There was a small amount of swelling, but nothing dramatic

In other words, there were no signs of a new structural injury.

What had happened was something more subtle — but incredibly important:

👉 The nervous system had temporarily down-regulated muscle output.

In an ACL-deficient knee, stability relies heavily on:

• Strong, well-timed quadriceps

• Supportive hamstring activity

• Good coordination and confidence

When those systems get overloaded — not necessarily by one big event, but by weeks or months of cumulative demand — the body can respond by pulling the handbrake.

The result?

• Muscles feel weak

• Movements feel shaky

• The joint feels “unstable”

• Confidence drops fast

Not because the knee has failed — but because the system is protecting itself.

Why this can happen after months of good progress

This is the part that really unsettles people.

They’ll often say:

“But I was doing so well… how can it suddenly be worse?”

Here’s the key idea:

Progress doesn’t mean you’re far from the edge — it often means you’re closer to it.

As rehab improves:

• You do more

• You rely on the system more

• Demands increase, even if consciously nothing has “changed”

Sometimes it only takes:

• A busy week

• Less recovery

• A bit of irritation

• A small amount of swelling

…for the system to say “That’s enough for now.”

This isn’t failure.
It’s feedback.

Zooming out: this isn’t just an ACL thing

Although this example comes from ACL rehab, the same pattern shows up across many types of pain and injury, including:

• Back pain that was improving, then suddenly flares

• A shoulder that feels weak and unreliable after months of rehab

• Tendon pain that “comes back” despite careful loading

• A knee or hip that feels unstable without a clear reason

• Pain that spikes during busy or stressful periods, not after injury

In all of these cases, the underlying mechanism is often the same:

Capacity has temporarily fallen below demand.

And when that happens, the body protects itself by:

• Reducing muscle output

• Increasing sensitivity

• Making movements feel harder and less trustworthy

That protection can feel alarming — but it’s rarely dangerous.

Why this doesn’t mean rehab has failed

This is one of the most important messages I give patients:

A flare-up is not the opposite of progress.

In fact, in demanding rehab journeys — especially ones that ask the body to adapt significantly — these moments are often part of success.

They tell us:

• Where current limits are

• How sensitive the system is to load

• What needs more recovery, not more pushing

Avoiding these moments entirely usually means:

• Not asking enough of the system

• Staying safely below your potential

The goal isn’t to never flare — it’s to recognise, manage, and recover from them well.

What actually helps in moments like this

Across conditions, the principles are remarkably consistent:

• Relative rest, not total shutdown

• Reducing background load, not panicking

• Restoring basic muscle activation

• Keeping joints moving comfortably

• Reassurance that nothing is “damaged”

Most importantly:

• Understanding what’s happening

Fear and uncertainty amplify symptoms.
Clarity and context reduce them.

The bigger picture: the body is adaptable — but adaptation has a cost

Choosing conservative rehab for something like an ACL tear is a powerful decision. It relies on the body’s ability to adapt, compensate, and reorganise.

That adaptability is incredible.

But it’s also demanding.

And occasionally, the system needs a pause, a reset, and a small step back — so it can keep moving forward.

If you’re going through something similar

If your rehab feels like it’s suddenly gone backwards:

• It doesn’t mean you’re broken

• It doesn’t mean you’ve “undone” everything

• It doesn’t automatically mean surgery or scans or starting again

Often, it means your body is asking for:

A recalibration — not a retreat.

And with the right guidance, those moments become stepping stones rather than dead ends.