Phase 5: Return to Running
You've made it to the penultimate phase of your ACL recovery. By now you should be walking confidently without any aids — that alone is real progress, so take a moment to acknowledge how far you've come.
Understanding your isokinetic test
Before progressing to running, you'll undergo an isokinetic test, which measures your limb symmetry index (LSI) — how your operated leg's strength compares to your other leg, expressed as a percentage. (We'll cover how to interpret this test in detail in a dedicated article — link coming soon.)
To safely begin real running, you need to reach at least 70% LSI. This threshold matters because running places significant load on a knee that's still rebuilding its strength and control.
If you haven't reached 70% yet
This is more common than you might think, and it's nothing to be discouraged about. Life gets in the way — work deadlines, exams, family responsibilities. We're not professional athletes with unlimited time for therapy and strength training, and that's simply the reality of living and healing in Singapore.
Interestingly, many patients experience a long plateau followed by a sudden, exponential jump in strength. If you're in the slower-progress group, that breakthrough is often still ahead of you.
From here, you have two reasonable paths:
- Push forward: keep training intensively, and we retest in about three months.
- Go at your own pace: continue building strength under your physiotherapist's guidance using the one-rep max (1RM) test in the gym, and we reassess at your planned one-year review.
Neither path is wrong. Be patient with yourself.
If you've reached 70% or more
Well done — this is a great milestone. Running is a foundational movement that underlies most pivoting sports, so this is where your return-to-sport journey really begins.
A few important principles as you build up your mileage:
- The 10% rule: increase your weekly running distance by no more than 10% over the previous week, to avoid overuse injuries.
- Cross-train wisely: cycling is a great low-impact way to build aerobic capacity alongside running.
- Watch for overuse injuries: shin splints and stress fractures are common when athletes ramp up too quickly. Work closely with your coach or physiotherapist.
- Support bone health: as you return to high-impact activity after a year away, keep up your calcium and vitamin D intake, along with regular sunlight exposure.
The most important warning: don't rush back to sport
It's tempting — running starts to feel normal again, and the urge to return to your sport grows. This is exactly the moment to hold yourself back.
Research shows that returning to sport before nine months post-surgery carries a substantially higher risk of re-injury [1]. A re-injury means a re-torn graft — and starting the entire recovery cycle over again. As surgeons, we're often accused of being overly cautious about return-to-sport timing, but consider the trade-off: a six-month delay is far better than a repeat injury that costs you another full year of surgery and rehabilitation.
Keep building strength through this phase — your goal is 90–100% LSI before returning to training. Don't neglect the gym even as your aerobic fitness improves.
- Grindem H, Snyder-Mackler L, Moksnes H, Engebretsen L, Risberg MA. Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med. 2016;50(13):804-808. doi:10.1136/bjsports-2016-096031