Fibular Osteochondroma and Peroneal Nerve Compression

The VerdictMODERATE CONVICTION

A dropped foot usually fixes itself. If there is a hard lump below your knee, this one will not.

Run your fingers down the bone on the outside of your shin, starting just below the knee. Feel for something hard and fixed. If you find one and your foot or big toe is weak, book an appointment this week and ask for an X-ray of the knee. In the reported cases, foot and ankle scans came back normal because the lump sits higher up.

Here is what is really happening: a small bony growth on the outside of your knee is pressing on the nerve that lifts your foot.
What most people get wrong: most dropped feet do recover on their own, so waiting is sensible advice in general, and it is the wrong advice when a lump of bone is doing the pressing.
Start here: ask for an X-ray of the knee, not the foot, because that is where the lump is and foot scans come back clear.

The nerve that lifts your foot runs over a bare bony corner just below the outside of your knee, like a cable draped over the edge of a desk with nothing padding it. Usually the thing pressing on that cable is your own position, so when you shift, the pressure lifts and the nerve recovers on its own. Here the thing pressing is a lump of bone growing out of the corner itself. It cannot shift, and in someone still growing it gets bigger, which is why the usual advice to wait is the one piece of advice that does not work.

What Works

Dark cinematic study of the lower leg and ankle in dramatic light

There is no strong-evidence tier here, and that is the honest starting point

No randomized trial, systematic review, meta-analysis or clinical guideline exists for this condition. Four separate literature searches across four databases returned none of any kind. Everything below rests on surgeons reporting what happened to their own patients, which is real information and is not the same as proof.

Surgery to free the nerve and remove the growth MODERATE

This is what every reported series does, and the results are consistent. Of nine patients who had a foot drop before surgery, five recovered completely, three improved and one did not (Birch 2021, 25 patients and 31 legs). Reported recoveries land at 3 months in two cases and full motor function at 8 months in another.

The risk figures belong in the same conversation. Across 126 limbs, seven people came out of the operation with a foot drop they did not have going in. Complications were more likely when the growth was at the front of the bone, when a bigger section of fibula was removed, and when the nerve had been operated on before (Huser 2024). About 14% of growths came back, and every single one of those was in someone who had not finished growing.

Removing a symptomatic bony growth generally MODERATE

Across 92 growths at all sites in the body, 93.4% of symptoms resolved, with major complications in 4.7%. All three nerve palsies in that series recovered after the nerve was freed (Bottner 2003). This is not specific to the fibula, so treat it as supporting rather than direct.

See the weaker options and what we genuinely do not know

Watching a growth that is causing no symptoms EMERGING

Most of these never press on the nerve. Only 12% of growths at this site ever produced nerve symptoms, and 71% of the ones that went to surgery had no foot drop at all. But nobody has ever followed a group of untreated growths properly, so the case for watching rests on the wrong kind of evidence and no follow-up schedule has been published.

A brace to hold the foot up EMERGING

Reasonable while you wait, and it does nothing to the growth. One caution worth knowing: the electrical stimulation devices sometimes offered for a dropped foot work by stimulating this exact nerve, and their evidence comes from a different kind of foot drop where the nerve itself is healthy. Do not assume they transfer here.

What Doesn't Work

Exercise as the main treatment. Nothing you do with muscles moves bone off a nerve, and no study has ever tested it. Time spent on a strengthening plan is time the pressure stays on.
Waiting to see whether it recovers. Right for most dropped feet, wrong for this one. The only reported case that went six years before diagnosis is also the only one left with permanent damage.
Scanning the foot and ankle. The lump is at the knee. One patient's foot and ankle X-rays were completely normal while the growth sat higher up the leg.
Testing the foot lift as one movement. One reported patient had complete wasting of the toe-lifting muscles with a normal ankle lift, because the branch to the ankle muscle leaves the nerve above where the growth was pressing.

Exercise Prescription

Read this before the table. No exercise programme has ever been tested for this condition. Not a thin evidence base, none at all. The movements below are borrowed from general dropped-foot care, and their only job is to stop the ankle stiffening while you wait for the specialist. They are not a treatment for the growth.

Movement	How to do it	Dose	How it should feel
Ankle circles	Sitting with the leg out, slowly draw circles with your foot both ways. Use your hands to help if the foot will not move on its own.	2 × 10 each way, daily	A gentle stretch, never sharp
Calf and heel-cord stretch	Stand facing a wall, back leg straight, heel down, lean forward.	3 × 30 seconds, daily	A stretch in the calf, not pain
Assisted toe and ankle lifts	Use your hand or a towel loop to pull the foot and toes upward through the full range.	2 × 10, daily	No pain. This keeps the joint mobile, it does not build strength

Return to Training

These are checkpoints, not a calendar. There is no published timeline for this condition, so the criteria are about what your leg can actually do.

The growth has been imaged and characterised, and a specialist plan is in place
Urgent causes ruled out: no vascular signs, no growth after skeletal maturity, no new numbness in someone with known multiple lumps
Ankle lift and big-toe lift both at grade 4 or better, tested separately from each other
No foot slap and no high-stepping over a 10 metre walk without a brace
Full ankle movement with no fixed stiffness
Ten controlled single-leg steps heel to toe without catching the toe
No worsening of numbness or weakness across two consecutive checks

See someone urgently if any of these apply

Dark cinematic anatomical study of the outer knee and upper shin

New numbness or weakness when you already know you have multiple bony lumps This can mean a lump has turned cancerous. It happens in 1% to 25% of people with the inherited form (Paik 2000). Needs urgent scanning and a specialist, not physical therapy.
A dropped foot together with a swollen or throbbing knee, or a lump you can feel pulsing This can be a damaged artery behind the knee rather than bone pressing on nerve (Onan 2014). Needs an urgent vascular opinion the same day.
A lump that is getting bigger after you have finished growing These growths are supposed to stop when your growth plates close. One that carries on needs imaging.
Weakness that is getting worse rather than staying the same The pressure on the nerve is still building. Waiting costs you recovery.

Where to go: orthopaedics for the growth itself. Vascular surgery for the swollen or pulsing knee. Orthopaedic oncology for new numbness in someone with known multiple lumps.

Run your fingers down the bone on the outside of your shin, starting just below the knee. Feel for something hard and fixed.

If you find one and your foot or your big toe is weak, book an appointment this week and ask for an X-ray of the knee. In the reported cases, foot and ankle scans came back clear, because the lump sits higher up than anyone was looking.

Takes about 30 seconds. No equipment needed.

The Verdict

A dropped foot usually fixes itself. If there is a hard lump below your knee, this one will not.

The nerve that lifts your foot runs over a bare bony corner just below the outside of your knee, like a cable draped over the edge of a desk with nothing padding it. Usually the thing pressing on that cable is your own position, so when you shift, the pressure lifts and the nerve recovers by itself. Here the thing pressing is a lump of bone growing out of the corner. It cannot shift, and in someone still growing it gets bigger, which is exactly why the usual advice to give it time is the one piece of advice that does not work.

Here is what is really happening: a small bony growth on the outside of your knee is pressing on the nerve that lifts your foot.
What most people get wrong: most dropped feet do recover on their own, so waiting is sensible general advice, and it is the wrong advice when a lump of bone is doing the pressing.
Start here: ask for an X-ray of the knee rather than the foot, because that is where the lump is and foot scans come back clear.

Best for

Someone with a weak or dropping foot who can feel a hard, fixed lump on the outside of the shin just below the knee.

Skip if

Your knee is swollen or throbbing, or you already know you have multiple bony lumps and have developed new numbness. That is urgent care today, not a reading list.

Want the full evidence? Keep scrolling

Conviction MODERATE

The parts of this differ enough that one badge would be dishonest, so here they are separately.

A growth at the fibular neck can compress this nerve HIGH
Surgery relieves the compression MODERATE
Earlier surgery produces better recovery LOW
Regrowth risk sits with those still growing MODERATE
Any rehabilitation parameter NO EVIDENCE

What would change my mind on "earlier surgery is better"

This is the weakest claim on the page and it drives the most urgent advice, so it deserves scrutiny. It rests on every author recommending it plus a single case that waited six years and kept a permanent deficit. Nobody has tested a cut-off. A study following at least 150 confirmed growths, recording the time from first symptom to surgery as a continuous number and measuring ankle strength at 12 months, would settle it. If that study found no relationship between delay and recovery, the urgency on this page would need rewriting.

What would change my mind on "surgery is the treatment"

Every reported series operates, so there is no comparison group anywhere in this literature. The missing arm is the one nobody has recruited: growths that were left alone and watched. Until somebody follows those, we know what happens to the operated and nothing about the alternative. That is a real gap, not a technicality, because the same operation caused a foot drop in seven of 126 limbs.

Before you go

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The Full Picture — Anatomy, Diagnosis & Evidence

What's Actually Going On

Dark cinematic anatomical study of the nerve path around the outer knee

The nerve that lifts your foot wraps around the neck of the fibula, the slim outer bone of the lower leg, with almost nothing covering it. Just past that corner it dives into a tight sleeve of tissue. It is the most exposed stretch of nerve in the leg, which is why so many different things can squash it.

A growth here has nowhere to expand except into the nerve. Elsewhere on the same bone there is soft tissue to push aside. Three things make this different from every other cause of a dropped foot: the growth does not dissolve, in someone still growing it gets bigger, and in two reported cases it grew straight through the middle of the nerve and split it into two strands (Gray 2004).

The nerve then splits into branches, and the branch that lifts your ankle leaves early, higher up than the branches that lift your toes. That single fact explains the most easily missed version of this condition.

How to Identify It

Dark cinematic study of the lower limb in clinical examination light

Feel along the fibular neck for a hard, fixed lump

Start at the bony bump on the outer knee and work down about 6 cm. Bone-hard and immobile, not a soft swelling. One reported growth sat exactly 6 cm below that bump.

NO PUBLISHED ACCURACY DATA

Tap over the nerve at the same spot

A tingling or electric feeling shooting into the foot points at the nerve being irritated right there. In the one case that reports it, this is what sent the patient for the correct X-ray.

NO PUBLISHED ACCURACY DATA

Test the big-toe lift on its own

Resist the big toe lifting, separately from the whole ankle. This is the test that catches the version where ankle strength is normal and only the toe-lifters have gone. One patient's toe-lifting muscles had wasted completely while the ankle tested fine.

NO PUBLISHED ACCURACY DATA

Those badges are not an oversight. Nobody has ever published how good these tests are for this condition, and a borrowed number from a different condition would be worse than no number at all.

Dark cinematic anatomical study contrasting structures around the knee

What else it could be: a dropped foot with no lump at all, which is the common case and usually recovers by itself; a fluid-filled cyst tracking along the nerve from the nearby joint; a soft nerve tumour, which feels rubbery and movable rather than bone-hard; a damaged artery behind the knee, which is urgent; or a trapped nerve in the lower back, which would also weaken turning the foot inward and pushing the hip out sideways, both of which stay strong here.

The Debate

There is no guideline for this condition and no trial, so the genuine argument is not old advice against new trials. It is that this case is the exception to a rule that is otherwise right.

The general rule, which is correct

Most squashed nerves at this spot recover on their own, and the published surgical success rates look better than they are because they are measured on people already selected for having failed to recover. When someone finally ran the trial, the people treated without surgery recovered slightly faster. This is the standing position across this library's other cards on the same nerve, and it is well argued.

Why it does not apply here

Every one of those arguments needs recovery to be physically possible without intervention. That works when the thing pressing is a position, a habit or lost padding, because all of those can change. A lump of bone cannot, and in a teenager it grows. Same nerve, same spot, different compressor, opposite conclusion. Usefully, the general card's own advice points straight here: it says to image in order to rule out a mass. This is the mass.

And the counterweight, from the same evidence

None of that makes this an argument for rushing to surgery. Only 12% of growths at this site ever caused nerve symptoms, 71% of those operated on had no foot drop at all, and the operation itself caused a foot drop in seven of 126 limbs. The case is for recognising it and referring it, not for operating on every lump.

Honest Limitations

The evidence is about children, and most readers are not

The largest study of nerve function here had an average age of 12.4 years. Another ran 18 to 25. The regrowth figure of about 14% is defined by not having finished growing, so it cannot describe a 40-year-old at all, and this page does not pretend otherwise.

This is rare, and the skill is spotting it, not managing it

A clinician will feel far more harmless bony bumps than compressive ones. The value of everything here is in about five minutes of examination, not in a twelve-week plan.

There is no rehabilitation evidence whatsoever

Not thin, none. No study reports an exercise, a dose, a brace comparison or a return-to-sport timeline for this condition. One paper refers its patient to physical therapy in its closing sentence and stops there. That sentence is the entire published literature on what happens next.

The Nuance

Surgery against waiting, with the numbers such as they are. There is no success rate for waiting, because nobody has studied it. For surgery, of nine patients with a foot drop beforehand, five recovered fully, three improved and one did not. Across all body sites, removing a symptomatic growth resolved 93.4% of symptoms with major complications in 4.7%.

What actually decides it. Not the recovery rate, but the pattern in the timings. Every reported case treated early recovered fully. The single case diagnosed six years after symptoms began kept permanent wasting of the toe-lifting muscles. That is one case and not a threshold, and nobody has tested a cut-off. What can be said honestly is that the six-year delay was a delay in working out what was wrong, not a decision to wait, and that is precisely the delay a careful examination prevents.

One more wrinkle worth knowing. In a 6-year-old with this exact problem, an ultrasound done before surgery found an extra nerve branch running an unusual course, which explained a muscle being involved that the standard map does not predict. The surgeon preserved both strands because they knew it was there. If the pattern of weakness does not fit the textbook, that is a reason to look harder, not a reason to drop the diagnosis.

Sources

Huser AJ et al., 2024 — J Bone Joint Surg Am. PMID 38662808. 126 limbs. Regrowth 13.8%, all in those still growing; 7 foot drops caused by the operation; complication risk higher for front-of-bone growths, larger resections and repeat surgery. RETROSPECTIVE SERIES
Birch CM et al., 2021 — J Pediatr Orthop. PMID 33003067. 25 patients, 31 legs, average age 12.4. Foot drop in 9 of 31 before surgery; 5 full recoveries, 3 improved, 1 persistent. RETROSPECTIVE SERIES
Abdel MP et al., 2010 — Clin Orthop Relat Res. PMID 20625947. 121 growths at this site; nerve symptoms in only 12%; 9 nerve palsies after surgery, 3 permanent. RETROSPECTIVE SERIES
Göçmen S et al., 2014 — J Neurosurg. PMID 24405073. 20 operated nerve injuries from these growths; good sensory recovery in all at an average of 3.9 years. CASE SERIES
Bottner F et al., 2003 — J Bone Joint Surg Br. PMID 14653600. 92 growths removed; 93.4% of symptoms resolved; major complications 4.7%. RETROSPECTIVE SERIES
Paprottka FJ et al., 2012 — JPRAS. PMID 22495012. Complete wasting of the toe-lifting muscles with a normal ankle lift; diagnosed 6 years after symptoms began; partially permanent. CASE REPORT
Gray KV et al., 2004 — J Pediatr Orthop B. PMID 15199286. Two cases where the growth passed through the nerve and split it in two. CASE REPORT
Yoo JH et al., 2010 — Arch Orthop Trauma Surg. PMID 19633864. Loss of big-toe lift as the only sign, with normal foot and ankle X-rays; full recovery at 3 months. CASE REPORT
Paik NJ et al., 2000 — Muscle Nerve. PMID 10918272. Nerve compression in known multiple growths that proved to be a cancerous change; transformation reported in 1% to 25%. CASE REPORT
Onan B et al., 2014 — Ann Vasc Surg. PMID 24326060. Foot drop in a 12-year-old caused by a damaged artery behind the knee, not by bone at the fibula. CASE REPORT
Lucchetta M et al., 2011 — J Pediatr Surg. PMID 21292098. 6-year-old; ultrasound before surgery found an extra nerve branch, and both strands were preserved. CASE REPORT

Full evidence trail: 22 sources, citation gate passed on first submission. No randomized trial, systematic review, meta-analysis or clinical guideline exists for this condition, confirmed across four separate literature searches and four databases.

A dropped foot usually fixes itself. If there is a hard lump below your knee, this one will not.

When a Dropped Foot Will Not Fix Itself

What Works

There is no strong-evidence tier here, and that is the honest starting point

Surgery to free the nerve and remove the growth MODERATE

Removing a symptomatic bony growth generally MODERATE

Watching a growth that is causing no symptoms EMERGING

A brace to hold the foot up EMERGING

What Doesn't Work

Exercise Prescription

Return to Training

See someone urgently if any of these apply

Best for

Skip if

Conviction MODERATE

What's Actually Going On

How to Identify It

Feel along the fibular neck for a hard, fixed lump

Tap over the nerve at the same spot

Test the big-toe lift on its own

The Debate

The general rule, which is correct

Why it does not apply here

And the counterweight, from the same evidence

Honest Limitations

The evidence is about children, and most readers are not

This is rare, and the skill is spotting it, not managing it

There is no rehabilitation evidence whatsoever

The Nuance

Sources

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