ACL Surgery With a Peroneus Longus Graft: Will Taking a Tendon From My Ankle Weaken It?

By Dr Markandaiya Acharya, Orthopaedic Surgeon

Picture a 24-year-old on a Sunday morning football ground. He plants his foot, turns to chase the ball, and feels something give way inside his knee. There is a pop. Within an hour the knee is swollen like a small melon.

A few weeks later the swelling has settled, but the knee has not. It buckles on the stairs. It wobbles when he turns quickly. The MRI report says what he feared: anterior cruciate ligament (ACL) tear.

He accepts that he needs surgery. Then the surgeon says something that stops him: "We will take a tendon from the outer side of your ankle to build your new ligament."

And the question I hear in my clinic almost every week follows immediately:

"Doctor, my knee is already damaged. Will you now spoil my ankle as well?"

It is a fair question. It deserves an honest, evidence-based answer. A large 2026 analysis gives us one.

A New Ligament Has to Come From Somewhere

A torn ACL rarely heals on its own in a way that restores stability. In ACL reconstruction, we do not stitch the old ligament. We replace it with a graft, usually a tendon taken from the patient's own body. This is called an autograft.

For years, the common choices have been the hamstring tendons from the back of the thigh, or part of the patellar tendon from the front of the knee. Both work well. Both also take something away from a knee that is already injured.

That is why surgeons, particularly across Asia, have increasingly turned to another option: the peroneus longus tendon.

Can You Really Spare a Tendon From Your Ankle?

The peroneus longus runs down the outer side of the leg, passes behind the outer ankle bone, and travels under the foot. It helps turn the foot outwards and supports the arch.

So the worry makes sense. If a tendon that steadies the ankle is removed, will the ankle become weak? Will it twist easily? Will running, squatting, or walking on uneven village roads become difficult?

Here is the part many patients do not know. The peroneus longus has a partner, the peroneus brevis, which runs alongside it and does much of the same work. The long-standing belief has been that this neighbour compensates.

But belief is not evidence. What do the numbers actually say?

What 20 Studies and 1,024 Patients Showed

A systematic review and meta-analysis published in the journal Knee Surgery, Sports Traumatology, Arthroscopy (September 2026) set out to answer exactly this question. The researchers pooled results from 20 studies involving 1,024 patients who had ACL reconstruction using a peroneus longus tendon graft. Nine of these were randomised clinical trials and eleven were prospective cohort studies.

They looked at two widely used ankle scoring systems, the AOFAS score and the FADI score. In both, 100 represents a fully normal, pain-free, well-functioning foot and ankle.

The pooled results:

• At 6 months: average AOFAS score of 96.0 and FADI score of 97.4
• At 12 months: average AOFAS score of 96.1
• At 24 months: average AOFAS score of 97.2 and FADI score of 99.4

In plain language: on these questionnaires, the donor ankle was functioning at very close to normal by six months, and it stayed that way at two years.

Two more findings matter to patients:

• Age made no significant difference. Older patients in these studies did not have meaningfully worse ankle scores than younger ones.
• No study reported a major nerve injury or ankle instability after the tendon was harvested.

What Can Go Wrong?

No operation is free of side effects, and you should be told about them before you sign a consent form, not after.

In the studies reviewed, minor complications occurred in roughly 13% to 23% of patients. The typical example was a patch of reduced sensation or numbness near the small cut on the outer leg. These settled within months.

So the realistic expectation is this: a noticeable minority of patients feel some temporary numbness around the ankle scar, and the evidence so far shows it recovers.

What We Know, and What We Do Not Yet Know

I would be doing you a disservice if I presented this as a closed question. Here is how I weigh it.

Reasonably well supported:

• Ankle function scores after peroneus longus harvest are consistently high up to two years.
• Serious donor-site problems were not reported in these studies.

Still uncertain:

• The authors themselves note that results varied considerably between studies.
• Most participants were men, and most studies came from Asian populations. That is actually relevant and reassuring for Indian patients, but it means we know less about women and other groups.
• Follow-up was up to two years. We do not yet have the same quality of evidence for ten or twenty years.
• Questionnaire scores are not the same as high-level performance testing. More recent research is examining whether fine, dynamic ankle control may be subtly affected even when strength and scores look good. This is emerging work, not settled fact, but it matters for athletes in jumping, cutting, and sprinting sports.

This study also looked specifically at the ankle. It was not designed to tell us which graft produces the best knee.

Choosing the Right Graft for You

There is no single graft that is right for everyone. The choice is a conversation, and these are the things I consider with each patient:

• Your sport and how much it depends on the ankle (a sprinter or badminton player is different from an office worker)
• Your occupation, including whether you squat, kneel, or sit cross-legged for long hours
• The size and quality of your hamstring tendons
• Whether other ligaments are injured, or whether this is a repeat operation
• Any previous ankle sprains or ankle instability on that side

If you have a history of repeated ankle sprains, tell your surgeon. It may change the plan.

What to Expect

Whichever graft is used, the operation is only the first half of the treatment. Rehabilitation is the second half, and it decides the result.

After ACL reconstruction with a peroneus longus graft, a good physiotherapy programme usually pays attention to both joints:

• The knee: regaining full straightening, controlling swelling, and rebuilding the thigh muscles step by step
• The ankle: gentle movement early on, followed by strengthening of the outer ankle muscles and balance training

Return to pivoting sport after ACL reconstruction is commonly a matter of many months rather than weeks, and it should be based on strength and movement tests, not on the calendar alone. Your own timeline must come from the surgeon and physiotherapist who examine you.

Be patient with numbness around the ankle scar if it occurs. Report it, but do not panic. Do report promptly if you notice the ankle repeatedly giving way, increasing pain, or swelling that is not settling.

Questions Patients Often Ask

Is the peroneus longus tendon graft safe for ACL reconstruction?

Current evidence from 20 studies suggests ankle function remains very close to normal up to two years after harvest, with no major nerve injuries or ankle instability reported. Long-term data are still limited.

Will my ankle become weak after peroneus longus graft harvest?

In pooled studies, ankle function scores averaged 96 to 99 out of 100. Most patients do not notice a problem in daily life. Research on high-demand athletic ankle control is still developing.

What are the side effects of taking the peroneus longus tendon?

The most commonly reported issue was temporary numbness or altered sensation near the harvest site, seen in about 13% to 23% of patients, which resolved within months.

Is peroneus longus better than hamstring graft?

This particular study did not answer that. It examined ankle outcomes only. The better graft is the one that suits your knee, your body, and your activities.

The Takeaway

If you have been told you need ACL surgery and your surgeon has suggested a peroneus longus graft, the fear of "damaging a healthy ankle to fix a bad knee" is understandable. The best available evidence says that fear is, for most patients, larger than the actual risk.

It is not zero risk. It is a small, mostly temporary cost, and one that should be weighed openly against the alternatives.

So do not ignore a knee that keeps giving way. An unstable knee can go on to injure its own cartilage and menisci each time it buckles. Get it examined, understand your MRI, and ask your surgeon three simple questions: Which graft do you recommend for me? Why? And what will my rehabilitation look like?

If you are looking for an orthopaedic doctor in Cuttack or the Banki area for a knee ligament injury or sports injury, you are welcome to come for an assessment and discuss your options in detail.

Dr Markandaiya Acharya
Orthopaedic Surgeon, Cuttack, Odisha

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Reference: Soleymanha M, Soleymani Nejad A, Keyhani S, Vosoughi F, LaPrade RF, Tollefson LV. Peroneus longus tendon harvest for ACL reconstruction yields good functional outcome of the ankle: A systematic review and meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2026;34(9):3233-3246. doi:10.1002/ksa.70079

Disclaimer: This article is for general patient education and is not a substitute for a consultation. The opening scenario is illustrative and does not describe a real patient. Treatment decisions should be made with your own doctor after examination.