Acute Peroneus Longus Tendon Rupture

Home / Acute Peroneus Longus Tendon Rupture

Sports Injuries · Tendon Rupture

Peroneus Longus Tendon Rupture

A patient guide by Mr Matthew Welck, Consultant Orthopaedic Foot & Ankle Surgeon, London and North London

A peroneus longus rupture is when the long tendon on the outer side of your ankle snaps completely. This tendon runs down behind the ankle bone, under the sole of your foot, to the big toe side. It can snap suddenly, for example when you twist your ankle, or it can give way after being worn down over time. It is more common in people with high-arched feet, and in people who have a small bone inside the tendon called the os peroneum. A second tendon next to it, the peroneus brevis, can do much of its job, so many people manage well after a rupture. Active people, and those who still have pain or weakness, often benefit from surgery. This guide explains how a rupture is diagnosed and the treatments available in London and North London.

At a Glance: Peroneus Longus Rupture

Key factPeroneus longus rupture
What it isA complete break of the peroneus longus tendon, usually where it bends under the foot. Sometimes it happens when a small bone in the tendon (the os peroneum) breaks
Who it affectsActive adults and sportspeople, people with high-arched feet, and people with diabetes, inflammatory arthritis (such as rheumatoid arthritis) or who have taken steroids
Main symptomsSudden pain or a ‘pop’ on the outer edge of the foot, bruising, swelling, and less power pushing off through the big toe
Key testsAn X-ray of the foot taken at an angle, ultrasound and MRI scans; a standing CT scan to check foot shape
First-line treatmentA walking boot for 4–6 weeks, then an insole and physiotherapy. This often works well for less active people
SurgeryRepairing the tendon, removing a broken os peroneum, or stitching the tendon to its neighbour, the peroneus brevis (tenodesis). If both tendons have snapped, a graft or tendon transfer
RecoveryA boot for about 6 weeks, then an insole and physiotherapy; back to sport usually in 3–6 months
EvidenceBased on small studies and expert agreement only

01

What Is a Peroneus Longus Rupture?

Peroneus longus is one of two tendons on the outer side of your ankle, called the peroneal tendons. It runs behind the bony bump on the outside of your ankle (the fibula), along the side of your heel, then bends sharply under your foot. It crosses the sole to attach near the base of the big toe. Its job is to turn your foot outwards and press the big toe side of your foot down. This supports your arch and gives you power when you push off to walk or run.

A rupture means the tendon has snapped right through, so the muscle can no longer pull on the foot. Many people have a small bone inside this tendon, called the os peroneum, where it bends under the foot. If this small bone breaks and the pieces pull apart, the tendon is in effect snapped, because the two ends are no longer joined.

Ruptures happen in three main places: where the tendon bends under the foot (the most common place), at a bony bump on the side of the heel, and behind the ankle bone. Once the tendon snaps, the muscle pulls the upper end back up towards the ankle. If it is left for many months, the muscle gets shorter and can be partly replaced by fat. This can limit the options for repairing it.

02

How Common Is It?

A complete rupture of the peroneus longus is not common. Most of what we know comes from reports of single patients and small groups of patients. It happens less often than problems with the neighbouring peroneus brevis tendon. Both tendons snapping together is usually seen only in severe or long-standing cases.

About one in five people have an os peroneum (studies report anywhere from 5% to 30%). It usually causes no trouble. A break in this small bone is one of the ways the tendon can fail. Doctors group this with other causes of pain from this bone under the name painful os peroneum syndrome (POPS).

Ruptures are often missed at first, because the injury can look like a sprained ankle or a broken bone on the outer side of the foot (a fifth metatarsal fracture). Patients often wait many months for the right diagnosis, so it is worth seeing a specialist early.

03

What Causes a Peroneus Longus Rupture?

A rupture is usually caused by a sudden injury, by a tendon that has been slowly worn down, or most often by both.

  • A sudden twisting injury: rolling your ankle inwards hard, especially with your toes pointed down, or a strong pull of the muscle while your foot is planted, can snap the tendon or break the os peroneum.
  • A high-arched foot: a high arch puts extra strain on the tendon. It can also come with a larger bony bump on the side of the heel, which the tendon rubs against until it gives way.
  • Wear and tear over time: repeated running, jumping and changing direction in sport can weaken the tendon where it bends under the foot. A fairly small injury can then snap it.
  • An os peroneum: if this small bone breaks or comes apart, it can split the tendon in two.
  • Health conditions and medicines: diabetes, inflammatory arthritis, steroid tablets or injections, and some antibiotics (called fluoroquinolones) can weaken tendons and make a rupture more likely.

04

What Are the Symptoms?

Your symptoms depend on whether the tendon snapped suddenly or gave way slowly over time.

  • Sudden sharp pain, sometimes with a ‘pop’, on the outer edge of the foot when the injury happens
  • Bruising and swelling along the outer edge of the foot and below the ankle bone
  • Tenderness on the outer side of the sole, where the tendon bends under the foot
  • Weakness when pressing the big toe side of the foot down, and less power when walking, running or standing on tiptoe
  • Feeling less steady on uneven ground
  • In long-standing cases, an ache on the outer side of the foot and, sometimes, a slow change in the shape of the foot

Because the peroneus brevis can still turn the foot outwards, a rupture is easy to miss in a quick check. The key test is checking the strength of the big toe side of the foot.

05

What Tests Might You Need?

Your surgeon will look at the shape of your foot, test the strength of each tendon and feel along the path of the tendon. Scans are then used to confirm the rupture, find exactly where it is and plan treatment.

  • X-ray taken at an angle (oblique X-ray): this shows the os peroneum clearly. If it has broken and the pieces have pulled apart, or it has moved up towards the ankle compared with an earlier X-ray or your other foot, the tendon has very likely snapped.
  • Ultrasound: a quick scan that shows the gap in the tendon and checks the peroneus brevis while your foot moves.
  • MRI scan: shows where the tendon has snapped, how far the end has pulled back, the health of the muscle and the state of the peroneus brevis.
  • Weight-Bearing CT: a scan taken while you stand. It shows the shape of your foot and heel, which matters if a high arch needs correcting at the same time.

If the rupture happened many months ago, the MRI shows how healthy the muscle still is. This helps decide whether the tendon can still be repaired, or whether a tenodesis or tendon transfer (explained below) is a better choice.

06

Non-Surgical Treatment Options

Many people with a peroneus longus rupture can be treated without surgery, especially if they are less active or have health problems that make an operation less safe. The two ends of the tendon will not join back together on their own. But the peroneus brevis still turns the foot outwards, and many people get back to comfortable everyday activity.

  • A walking boot for 4–6 weeks to calm the pain and swelling
  • A made-to-measure insole to support your foot and take pressure off the outer edge
  • Physiotherapy to strengthen the peroneus brevis and calf, improve balance and help you build up activity step by step
  • Supportive shoes, and an ankle brace for sport or uneven ground
  • Simple painkillers, or a short course of anti-inflammatory tablets if they are suitable for you

Losing the peroneus longus mainly weakens pushing off through the big toe, so many less active people do well with just an insole. Surgery is usually advised for active people and sportspeople who want their push-off power back, if the os peroneum has broken and the pieces have moved apart, if pain or wobbliness carries on despite good non-surgical treatment, or if a high arch is putting the rest of the foot at risk.

If you are thinking about surgery, it helps to decide early. A rupture treated in the first few weeks can often be stitched back together. One that has been left for longer is more likely to need a tenodesis or tendon transfer.

07

Surgical Options for Peroneus Longus Rupture

The right operation depends on how long ago the tendon snapped, where it snapped, the health of the tendon and muscle, the state of the peroneus brevis and the shape of your foot.

Early Repair and Removal of the Os Peroneum

If the rupture is recent and the tendon ends are healthy, they can be stitched back together through a cut along the outer edge of the foot. If the os peroneum has broken, the broken pieces are removed and the tendon ends are stitched together, or the tendon is fixed back onto bone. If the rupture is at the side of the heel, the bony bump there is smoothed down at the same time. Any split in the peroneus brevis is repaired during the same operation.

Joining the Tendon to Peroneus Brevis (Tenodesis)

This is the most common operation when the rupture is long-standing, or when the lower end of the tendon is too damaged to repair. The damaged end of the peroneus longus is removed. The healthy upper part is then stitched into the peroneus brevis behind the ankle, so the peroneus longus muscle helps the peroneus brevis pull. It does not bring back push-off power through the big toe, but it reliably eases pain and keeps strength for turning the foot outwards. In one study of 12 patients who had the os peroneum removed and a tenodesis, foot scores improved from 61 to 92 out of 100, and pain scores dropped from 6.3 to 1.0 out of 10.

Rebuilding the Tendons When Both Have Snapped

If the peroneus brevis has also snapped or is too damaged to use, the choice of operation depends on whether the muscles still work. If they do, the gap can be bridged with a piece of tendon (a graft). If the muscles have become scarred and no longer move, a healthy tendon from elsewhere in the foot (flexor hallucis longus or flexor digitorum longus, which bend the toes) can be moved across to do the job of the peroneal tendons. This approach follows a well-known system for these combined injuries, described by Redfern and Myerson.

Correcting a High-Arched Foot

A high arch is the most common reason a repair fails, because it keeps overloading the outer side of the foot. If you have a high arch, extra procedures may be added: cutting and moving the heel bone (calcaneal osteotomy), cutting the bone behind the big toe to lower that side of the foot (first metatarsal osteotomy), and tightening the ligaments if the ankle is unstable. A standing CT scan helps plan these. A tenodesis is sometimes used in its own right as part of correcting a high-arched foot.

Comparing the Main Treatment Options

OptionWhen it is usedWhat to expect
Insole and physiotherapyLess active people; ruptures with little painOften enough; the peroneus brevis takes over and most people cope well
Repair, with or without removing the os peroneumRecent rupture with healthy tendon ends; a broken os peroneum with the pieces pulled apartPuts the tendon back as it was and best keeps push-off power
Tenodesis (joining to peroneus brevis)Older rupture, or the lower end of the tendon is too damagedReliable pain relief; peroneus brevis takes over
Tendon graft or transferBoth tendons snapped or too damaged to useRestores strength for turning the foot outwards; longer recovery
Correcting foot shapeHigh-arched footAdded to protect the repair and stop it failing again

Recovery After Surgery

After surgery, you will usually wear a splint and keep weight off your foot for about two weeks while the wound heals. You then wear a walking boot until about six weeks, slowly putting more weight through the foot. After that, you will have an insole and physiotherapy to build strength, balance and push-off. Many people can go back to desk work after two to three weeks. Getting back to sport usually takes three to six months, and sometimes longer after a graft or tendon transfer.

As with any operation, there are risks. These include slow wound healing, irritation of a skin nerve on the outer side of the foot (the sural nerve), stiffness, ongoing pain under the outer side of the foot, the tendon snapping again, and blood clots. In the study mentioned above, 3 of the 12 patients had slow wound healing and 2 had nerve symptoms.

08

Why Choose Mr Welck?

Mr Matthew Welck is a Consultant Orthopaedic Foot & Ankle Surgeon at the Royal National Orthopaedic Hospital (RNOH), Stanmore, and Honorary Associate Clinical Professor at University College London (UCL).

He works only on the foot and ankle, with clinics in Central and North London. He is a senior surgeon at the RNOH, one of the UK’s leading specialist orthopaedic hospitals, where other surgeons send their more complex cases. He regularly sees patients with peroneal tendon ruptures, painful os peroneum syndrome and high-arched feet.

Sports injuries are a large part of his work. Where helpful, he uses Weight-Bearing CT (a scan taken while you stand) to see your foot under load and find out why the tendon failed. He also performs total ankle replacement, complex reconstruction and revision surgery, so if a long-standing tendon problem has affected your joints, everything can be looked after in one place.

Mr Welck is an active researcher with more than 50 published scientific papers. He sits on the BOFAS (British Orthopaedic Foot & Ankle Society) Education Committee and teaches senior trainee surgeons how to manage tendon ruptures. He will always talk through your options with you, so you can decide on your treatment together.

09

Frequently Asked Questions

What is a peroneus longus rupture?

It is when the peroneus longus tendon snaps completely. This tendon runs along the outer side of your ankle and under your foot to the big toe side. It most often snaps where it bends under the foot, sometimes through a small bone in the tendon called the os peroneum.

What is the os peroneum?

It is a small bone inside the peroneus longus tendon, where the tendon bends under the foot. About one in five people have one. It usually causes no problems, but if it breaks and the pieces pull apart, the tendon is in effect snapped.

Do I need surgery for a peroneus longus rupture?

Not always. Many less active people do well with a boot, an insole and physiotherapy. Surgery is usually advised for active people, if the os peroneum has broken and the pieces have moved apart, or if pain or weakness carries on despite good non-surgical treatment.

Is it better to have surgery early?

If you are likely to need surgery, yes. A recent rupture can often be stitched back together. If it is left for many months, the tendon end pulls back and the muscle shortens, so a tenodesis or tendon transfer is more likely to be needed.

Can I manage without my peroneus longus tendon?

Often, yes. Its main job is pressing the big toe side of your foot down. Many people, especially those who are less active, manage well without it. The tenodesis operation uses the peroneus brevis to take over its pull.

Why do I need an X-ray taken at an angle?

This angled (oblique) X-ray shows the os peroneum clearly. If the bone has broken, or has moved up towards the ankle, it is a strong sign that the tendon has snapped.

How long is recovery after surgery?

Usually about six weeks in a splint and then a boot, followed by an insole and physiotherapy. Most people get back to sport in three to six months.

Why does the shape of my foot matter?

A high-arched foot puts extra strain on the peroneal tendons. If the arch is not corrected during surgery, the repair is more likely to fail.

Where can I see a foot and ankle specialist in North London?

Mr Matthew Welck sees patients with peroneal tendon problems and sports injuries at Spire Bushey, HCA The Wellington Hospital Elstree and the RNOH Private Patients Unit in North London, and at HCA The Princess Grace Hospital in Central London.

10

Book a Consultation

If you think you may have snapped your peroneus longus tendon, or you have pain and weakness on the outer edge of your foot after an injury, seeing a specialist early gives you the most treatment options. Mr Welck sees private patients (insured and self-funding) and NHS patients at the following locations:

  • HCA The Princess Grace Hospital, Central London (outpatients at Nottingham Place, W1U 5NY and 30 Devonshire Street, W1G 6PU)
  • HCA The Wellington Hospital Elstree, North London
  • Spire Bushey, North London (0203 733 5665)
  • RNOH Private Patients Unit, Stanmore, North London

Telephone 07547 395 270, email secretary@matthewwelck.com or book a consultation online. Patients are seen from across London, Hertfordshire, the UK and overseas.

Written and medically reviewed by Mr Matthew Welck

MBChB FRCS (Tr&Orth), Consultant Orthopaedic Foot & Ankle Surgeon, RNOH Stanmore; Honorary Associate Clinical Professor, UCL. GMC 6074385.

Last reviewed: October 2026. Next review due: October 2027.

This guide is for general information and does not replace an individual consultation. Treatment decisions should be made with a clinician who has examined you.

Written by: Matthew Welck | Consultant Orthopaedic Foot & Ankle Surgeon London — last updated 22 October 2026

CALL ME
+
Call me!
/ GMC No. 6074385