Peroneal Nerve Palsy After Knee Replacement

The VerdictMODERATE CONVICTION

After a knee replacement the nerve that lifts your foot can get stretched.

Sit down and try three things on the affected side. Lift your foot up towards you. Push your foot down as if pressing a pedal. Turn the sole of your foot inward. If only the first is weak and the other two are normal, that fits a nerve problem at the knee. If pushing down or turning inward is also weak, tell your surgical team today, because the problem is higher up.

What this actually is: the nerve that lifts your foot wraps around a bony corner just below the outside of your knee, where it sits close to the surface with almost nothing protecting it, and straightening a badly bent knee stretches it right there.
The one thing that makes it worse: assuming it is the anaesthetic block wearing off, because that is how a tight dressing stays on past the short window in which loosening it would have helped.
The first thing to start doing: get a brace fitted so you can walk without tripping, and move the ankle by hand every day so it does not stiffen into a pointed-down position.

Think of the nerve as a charging cable routed tightly around a sharp table corner. Straightening a badly bent knee pulls that cable taut over the corner, and a tight bandage presses it flat against it. The wire inside is not cut, it is squashed, so the signal drops out. Cables like this do repair themselves, but the insulation has to rebuild along the whole length of the crushed section, and that runs at roughly a millimetre a day rather than overnight. That is why this is measured in months.

Treatment

What Works

Cinematic anatomical rendering of the lower leg and ankle

Grade the palsy complete or incomplete at the first assessment High

This one distinction is the prognosis. Complete recovery ran 66% for incomplete palsy against 39% for complete palsy across 47,585 knee replacements (Carender 2020), and 75% against a single patient in a matched case-control study (Park 2013). It is the only prognostic variable in this condition that replicates, it costs nothing, and it can only be captured at the start.

Watchful waiting with structured review High

For an isolated, non-progressive palsy with normal pulses and no lump. Two thirds of incomplete palsies recover completely with no further surgery (Carender 2020), and motor recovery was complete or near-complete within a year in every followed case in the only series that ran nerve tests on all 54 patients (Speelziek 2019).

Release constrictive dressings and flex the knee, immediately Moderate

Mechanism established, never tested against an alternative. This has been the stated first treatment since 1982 (Rose 1982). It is kept because the mechanism is sound, the cost is zero, and the window in which it helps is short.

Screen for a proximal or blood vessel cause before starting rehabilitation Moderate

Twelve of 54 consecutive nerve injuries after knee replacement were sciatic or plexus level rather than peroneal (Speelziek 2019), and documented vascular and space-occupying causes exist (Ghazala 2015, Deshmukh 2014).

Exercise Prescription

Read this first. There has never been a research study on exercises or braces for foot drop after a knee replacement. Every number below is a conventional safe starting point that physical therapists use for foot drop generally. It is not taken from a study of this situation, because that study does not exist. Your physical therapist should adjust all of it to you. No evidence

Ankle pumps and alphabet. Sitting or lying, move the foot up and down as far as it goes, then draw the alphabet with the big toe. 2 rounds · 3-4× daily · Gentle stretch, no sharp pain.

Assisted toes-up. Loop a towel around the ball of the foot and gently pull the foot towards you. Hold. 3 × 30 sec holds · 3× daily · A calf stretch is fine, stop if sharp.

Active toes-up, as strength returns. Try to lift the foot without the towel. Even a flicker counts. 3 × 10 · daily · No pain. This is about the signal getting through.

Seated heel raises and toe raises. Sitting, lift the heels off the floor, then lift the toes off the floor. 3 × 15 each · daily · Comfortable.

Standing balance with support. Holding a counter, stand on the affected leg as long as is safe. 3 × up to 30 sec · daily · Hold on. Do not risk a fall.

Your knee replacement rehabilitation, unchanged. As prescribed · The foot drop does not pause it, and stiffness is its own problem.

Training, if you lift. Pull squats, deadlifts, lunges, running and loaded carries, because a foot that will not lift is a trip hazard under load. Keep all upper-body and seated lower-body work at full load. This is a specific restriction, not a reason to shut everything down.

What doesn't work

Waiting it out as "the block." A delayed foot drop after a supposedly motor-sparing nerve block is documented (Sreckovic 2021), and treating the block as the explanation is how a compressive dressing stays on past the point where removing it helps.
Quoting a single recovery percentage. Complete and incomplete palsies differ by 39% against 66% (Carender 2020). One average number is wrong for every individual patient.
Promising that a prophylactic nerve release protects the nerve. Five patients developed a palsy despite having had one (Rose 1982), and no controlled comparison exists.
Assuming the lesion is at the knee. It was sciatic or plexus level in 12 of 54 consecutive cases (Speelziek 2019).
Forcing a foot that is already fixed in a pointed-down position. That is a different problem from a floppy foot drop and needs orthotic and surgical input, not effort.

Safety First

Red Flags

Most of these recover. A small number are something else wearing this condition's clothes, and those are time-critical.

Cinematic anatomical rendering of the knee and popliteal region

Get seen urgently if

The back of your knee becomes swollen, painful or pulsing, or your foot turns cold, pale or dusky. Go to the emergency department. This can be a popliteal artery pseudoaneurysm, a blood vessel problem that presents as a nerve problem (Ghazala 2015).
The weakness is getting worse rather than better, or new weakness appears elsewhere in the leg. Call your surgical team the same day. A deficit that progresses after being stable suggests something expanding, not a stretched nerve.
You also cannot push your foot down, or turn the sole inward, or your ankle reflex has gone. Call your surgical team the same day. That means the problem sits higher than the knee, which was the case in 12 of 54 consecutive patients (Speelziek 2019).
The knee becomes hot or swollen, starts leaking, or you develop a fever. Possible infection. Surgical team, urgently.
You find any red mark, blister or broken skin under a brace or on the top of your foot. Where you are numb you cannot feel a rub forming. Tell your physical therapist.
A foot drop appears months or years after an uneventful knee replacement. That points at the implant rather than the operation, and needs x-rays (Deshmukh 2014).

Milestones

Return to Training

Cleared by the operating surgical team for the relevant activity level.
Grade 4 or better strength lifting the foot and the big toe.
No foot slap and no high-stepping gait on level ground, without the brace.
Twenty unbroken single-leg heel raises and 20 controlled toe raises on the affected side.
Single-leg stance on the affected leg for 30 seconds without hand support.
Full passive ankle movement, with no fixed pointed-down position.
Intact skin over the top of the foot, with daily checks if sensation is still reduced.
No progression of any neurological sign over the preceding four weeks.
Can descend a flight of stairs and step over a 15 cm obstacle without catching the toes.

These criteria are clinical reasoning, not study-derived. No return-to-activity milestone has ever been published for this population.

Do This Now

The Takeaway

Sit down and try three movements on the affected side. Lift your foot up towards you. Push your foot down as if pressing a pedal. Turn the sole of your foot inward.

If only the first one is weak and the other two are normal, that fits a nerve problem at the knee. If pushing down or turning inward is also weak, tell your surgical team today, because it means the problem is higher up.

The Verdict

What This Actually Means

After a knee replacement the nerve that lifts your foot can get stretched. Most people recover.

What this actually is: the nerve that lifts your foot wraps around a bony corner just below the outside of your knee, where it sits close to the surface with almost nothing protecting it, and straightening a badly bent knee stretches it right there.
The one thing that makes it worse: assuming it is the anaesthetic block wearing off, because that is how a tight dressing stays on past the short window in which loosening it would have helped.
The first thing to start doing: get a brace fitted so you can walk without tripping, and move the ankle by hand every day so it does not stiffen into a pointed-down position.

Best for

Someone recovering from a knee replacement with new weakness lifting the foot, normal pulses in the foot, and symptoms that are stable or improving.

Skip if

The weakness is getting worse, the back of the knee is swollen or pulsing, the foot is cold or pale, or you also cannot push the foot down or turn it inward. Those need urgent assessment, not a protocol.

Want the full evidence? Keep scrolling

Trust Anchor

Conviction

Moderate overall Scored per endpoint, because the evidence is not evenly distributed.

Claim	Conviction
Incidence 0.37% to 0.4% under tight case definitions	High
Recovery is severity-stratified, incomplete far better than complete	High
Roughly a fifth of these neuropathies are not peroneal at all	High
Anaesthetic technique does not cause the injury	Moderate
Any individual patient risk factor	Low
Prophylactic peroneal nerve release	Low
Rehabilitation and orthotic management	No evidence

"No evidence" is a different claim from "low." Nothing has been measured.

What would change the recovery figures

These come from observational cohorts, not trials, and the largest is a systematic review that pooled qualitatively rather than statistically, so there is no confidence interval on the headline 0.4%. A prospective multicentre registry that graded every palsy at onset and followed all of them to two years would either tighten these numbers or move them.

What would change the rehabilitation verdict

A randomised trial of at least 150 patients, allocated at diagnosis to early ankle-foot orthosis plus structured gait retraining versus usual care, followed 24 months with walking speed and brace dependence as the primary endpoints. It would be the first rehabilitation evidence this condition has ever had, and a null result would be as useful as a positive one because it would license honest counselling.

Next Step

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The Full Picture — Anatomy, Diagnosis & Evidence

What's Actually Going On

Cinematic anatomical rendering of the peroneal nerve at the fibular neck

The common peroneal nerve wraps around the neck of the fibula, just below and behind the bony bump on the outside of the knee. At that point it lies directly against bone with skin and almost nothing else over it. It is the most exposed nerve in the lower limb, and a knee replacement puts stress through exactly that spot.

Four mechanisms produce an identical picture, and they are not interchangeable. Which one is operating decides whether the right response is to loosen a bandage, to wait, or to call a vascular surgeon.

1. Traction. Correcting a fixed knock-knee deformity or a knee that will not straighten lengthens the soft tissue on the outside and back of the knee while the nerve stays tethered around the fibular neck. In the original series, 14 of the affected knees had fixed bends and 11 had knock-knee deformity (Rose 1982). The deformity is the exposure, not the implant.

2. Compression. A tight postoperative dressing presses the nerve against bone at its one unprotected point. The stated treatment since 1982 has been a looser dressing with the knee bent (Rose 1982).

3. Space-occupying and blood vessel lesions. A popliteal artery pseudoaneurysm (Ghazala 2015), a large fabella bone (Shen 2021) and late loosening of the implant (Deshmukh 2014) all cause foot drop by pressing on the nerve. These are the ones that arrive late, get worse, or come with a lump or a pulse change.

4. Anaesthetic. A delayed foot drop is documented after a combined adductor canal and IPACK block (Sreckovic 2021). Whether anaesthetic technique actually causes nerve injury is a separate question, and the answer appears to be no: anaesthesia type did not correlate with neuropathy in the series with nerve testing on every patient (Speelziek 2019), and epidural anaesthesia was not associated across 1,476 replacements (Schinsky 2001). The block can hide the problem without having caused it, and those are two different claims.

How to Identify It

Cinematic anatomical rendering of ankle and foot musculature

Diagnosis is a motor and sensory examination plus a timeline. There is no special test, and that is worth stating plainly rather than papering over.

Weakness lifting the foot upward. Sn: not measured Sp: not measured
Weakness extending the big toe, often the first to go and the last to return. Sn: not measured Sp: not measured
Numbness over the top of the foot and the outer shin. Sn: not measured Sp: not measured
Preserved downward push, inward turn of the sole, and ankle reflex. All three should be normal. Any abnormality moves the problem higher up.

"Not measured" means never measured, not "we could not find it." No sensitivity, specificity or likelihood ratio has ever been published for any bedside test in this condition against a nerve-test or surgical reference standard.

Cinematic anatomical rendering of lower limb nerve pathways

What else it could be. A residual anaesthetic block resolves within its expected window and does not progress. A sciatic or plexus lesion adds hamstring or downward-push weakness and takes the ankle reflex with it. An L5 nerve root problem weakens inward turn and hip abduction too. A pseudoaneurysm changes the pulses. Late loosening of the implant shows on an x-ray. And a distinct group has lateral knee pain or a stiff knee with normal strength and abnormal nerve tests, which responds to decompression (Zywiel 2011).

The Debate

No guideline exists

No clinical practice guideline addressing this complication was identified as of August 2026. There is no NICE, APTA, BOA, EULAR or ACR guidance on recognising, rehabilitating or referring it. That gap is the honest headline: a complication with a known rate, a known prognosis, and no guideline.

"Recovery is poor" against "recovery is good"

The 1982 series reported only 28.6% of motor deficits fully resolving and no sensory deficit resolving in any of 18 patients (Rose 1982). Modern series report complete or near-complete motor recovery within a year in all followed cases (Speelziek 2019). Which to follow: both, applied to the correct severity. The split is severity-driven, not era-driven. Complete palsy 39%, incomplete palsy 66% (Carender 2020). The historic pessimism is really a statement about complete palsies, and for those it still broadly holds.

Does the nerve block cause it?

Both studies that tested causation found nothing: anaesthesia type did not correlate with neuropathy (Speelziek 2019), and epidural anaesthesia was not associated (Schinsky 2001). The masking case stands separately (Sreckovic 2021). Which to follow: the null on causation, the vigilance on masking. Merging the two produces either false reassurance or a false accusation.

Honest Limitations

There is no rehabilitation evidence in this condition at all

Not one trial, cohort or case series of orthotic, physical therapy or exercise management after knee-replacement peroneal palsy was found by any search run for this page. Brace type, gait retraining dose, strengthening progression and time to full weight-bearing are all unstudied here. That is a gap in what researchers chose to study, not a low success rate, and the distinction matters because the first one is fixable.

The outcome measures are the surgeons', not the patient's

Every cohort reports recovery as a muscle grade or as complete against incomplete. None report walking speed, falls, brace dependence or return to work. We know how these nerves recover and almost nothing about how these patients walk.

The evidence base for this page is narrower than the published field, by a known amount

Six further papers relevant to this condition were located and verified during research but could not be cited, because the literature retrieval tool cannot reach them. No claim on this page rests on any of them. The two areas thinner as a result are the patient-level risk factors and the knock-knee-specific rate, both flagged where they appear.

The Nuance

Most of these recover on their own, and the ones that recover on their own never reach a surgeon. That is why the surgical series look so good.

The conservative numbers: for an incomplete palsy, 66% complete recovery with no further surgery across 129 graded palsies within a review of 47,585 replacements (Carender 2020), and independently 75% in a matched case-control series (Park 2013). For a complete palsy, 39%, and in the matched series only one patient.

The surgical numbers are not comparable, and the reason matters. The available series are five patients treated early, all recovering at a mean of 12 weeks (Johnson 2021), and eleven patients with nerve dysfunction rather than palsy, gaining a mean 40 degrees of knee movement (Zywiel 2011). Both are uncontrolled, neither has a comparison arm, and the early series selected patients who all had a knock-knee deformity and normal foot lifting before surgery. No study has ever randomised, or even matched, surgery against conservative care for this complication.

Read any uncontrolled surgical success rate here as a statement about who was left, not about what the operation did. The genuinely useful clinical work is not choosing between the two paths. It is grading the palsy correctly at the start, excluding the vascular and higher-up causes that need somebody else, and then protecting the foot and the ankle joint through a recovery that may take a year.

Evidence

Sources

Carender CN, et al. (2020). Common Peroneal Nerve Injury and Recovery after Total Knee Arthroplasty: A Systematic Review. Arthroplasty Today. PMID 32875016. Systematic review, 11 studies, 47,585 knee replacements, 203 palsies. The largest synthesis available.
Speelziek SJA, et al. (2019). Clinical spectrum of neuropathy after primary total knee arthroplasty: A series of 54 cases. Muscle & Nerve. PMID 30897216. The only series with systematic nerve testing on every case.
Park JH, et al. (2013). Common peroneal nerve palsy following total knee arthroplasty: prognostic factors and course of recovery. Journal of Arthroplasty. PMID 23562462. Matched case-control, 44 palsies against 100 controls.
Rose HA, et al. (1982). Peroneal-nerve palsy following total knee arthroplasty. J Bone Joint Surg Am. PMID 7061551. 2,626 arthroplasties. Historic, and its mechanism observations have aged better than its outcomes.
Schinsky MF, et al. (2001). Nerve injury after primary total knee arthroplasty. Journal of Arthroplasty. PMID 11740762. 1,476 primary replacements, 19 events. A null of low statistical power.
Zywiel MG, et al. (2011). Peroneal nerve dysfunction after total knee arthroplasty: characterization and treatment. Journal of Arthroplasty. PMID 20570090. 11 decompressions in patients with intact strength.
Johnson DB Jr, et al. (2021). Acute Common Peroneal Nerve Decompression After Total Knee Arthroplasty. Orthopedics. PMID 34292814. Five patients, uncontrolled.
Sreckovic SD, et al. (2021). Delayed foot drop after a combination of the adductor canal block and IPACK block following total knee arthroplasty. Journal of Clinical Anesthesia. PMID 34098393.
Ghazala CG, et al. (2015). Popliteal Artery Pseudoaneurysm with Secondary Chronic Common Peroneal Nerve Neuropathy and Foot Drop after Total Knee Replacement. Annals of Vascular Surgery. PMID 26140945.
Deshmukh AJ, et al. (2014). Delayed peroneal nerve palsy after total knee arthroplasty, a rare complication of tibial osteolysis. The Knee. PMID 24262809.
Shen K, et al. (2021). Common Peroneal Nerve Palsy Due to Giant Fabella After Total Knee Arthroplasty. Orthopaedic Surgery. PMID 33624373.
Myers MA, Harmon RL (1998). Sacral plexopathy and sciatic neuropathy after total knee arthroplasty. Electromyography and Clinical Neurophysiology. PMID 9809230.