Pain guide · Knee pain

Hyperextended knee: injuries when the knee bends backwards, and knees that bend back naturally

A hyperextended knee is one forced backwards past straight, in a fall, a tackle or a bad landing. The injury can range from a mild sprain at the back of the knee or a bone bruise to a torn anterior cruciate ligament (ACL), posterior cruciate ligament (PCL) or outer corner of the knee and, rarely, a dislocated knee. That's why this guide starts with the warning signs: a pop, quick swelling, a knee that gives way, and a numb or cold foot after a severe injury.

It then covers the X-ray rule and scans, how long sprains and bone bruises take, a staged plan with 3D demos that never forces the knee back, and where the ligament guides take over. Separately, it explains knees that bend back naturally (genu recurvatum and hypermobility): how far is normal, what it does and doesn't mean for injury risk, and the strength and control work that helps when it causes trouble.

4-stage exercise plan When to get help 32 sourcesUpdated 21 October 2026

When to get help first

Exercise is for pain that has been checked or is clearly mild and settling.

Get urgent medical help if

Call 999 or go to A&E after a high-energy injury, such as a car crash, a fall from a height or a heavy tackle, if the knee looks deformed or felt as if it came out of joint, the foot is cold, pale or numb, or you can't lift your foot or toes. The knee may have dislocated, which can damage the artery and nerve behind it, even when a pulse can still be felt. Don't drive yourself.
Call 999 or go to A&E if you heard a crack when you were injured, the knee has changed shape or points at an odd angle, the leg below it is numb or tingling, or the skin has changed colour or is cold to touch. You may have broken a bone. Don't drive yourself.
Signs of a torn ligament: you felt or heard a pop, the whole knee swelled within a few hours, or it gives way, feels loose or bends further back than the other knee. Get it assessed promptly, the same or the next day: our ACL, PCL and outer knee ligament (LCL) guides explain what happens next.
Same day, after the knee was forced backwards and outwards: numbness or tingling on the top of the foot or the outer shin, or difficulty lifting the front of the foot and toes (foot drop). Go to A&E or an urgent treatment centre, or get help from NHS 111. The nerve that lifts the foot runs past the outer knee, and it can be injured in more serious outer-knee injuries.
You cannot move the knee or put any weight on it, or it is very painful, badly swollen or has changed shape.
You hurt your knee and cannot take 4 steps, or you are 55 or over and hurt it in a fall: get it checked the same day for a broken bone.
The knee is locked and you cannot fully straighten it.
Throbbing pain and swelling in one calf or thigh, with red or darkened skin or swollen veins: ask for an urgent GP appointment or get help from NHS 111, as it could be a blood clot. Call 999 or go to A&E if you are also short of breath or have chest pain.

See a doctor or physiotherapist if

Knee pain that has not improved within a few weeks of looking after it at home. Many areas offer NHS physiotherapy without a GP referral.
The injury isn't feeling any better after treating it yourself, or the pain or swelling is getting worse: get help from NHS 111.
Pain at the back of the knee, or a feeling that the knee goes back too far, weeks after a hyperextension, even if a scan was normal: ask for a specialist examination.
A child or teenager with a knee injury: get it checked, because the growth plate can be injured, or a piece of bone pulled off with the ligament, instead of the ligament tearing.
Knees that bend back, with joint pain, repeated sprains, joints that slip out, tiredness or poor balance: see a GP about joint hypermobility syndrome.
A knee that snaps back when you walk after a stroke or with a neurological condition: ask your physiotherapist or orthotist.

Understand it

What happens in a hyperextension injury

The knee is forced past straight: a planted foot as the body falls backwards, a blow to the front of the shin with the leg straight, a tackle, or a landing on straight legs. The front of the shin bone and the end of the thigh bone are squashed together, leaving matching ('kissing') bone bruises that show on MRI (magnetic resonance imaging), while the structures at the back of the knee are stretched. The list below shows what can be hurt.

The PCL: the American Academy of Orthopaedic Surgeons (AAOS) lists a twisting or hyperextension injury among its causes.
The ACL, less often. In a review of 30 studies of bone bruises after ACL tears, the bruise pattern that suggests hyperextension was uncommon (3.5% to 6.8% of shin bone bruises); most ACL tears come from changing direction, stopping or landing badly.
The back of the joint capsule: hyperextension is one of the main ways it tears, and those tears are easily missed on examination and MRI.
The outer back corner of the knee (the posterolateral corner), from a force backwards and outwards. In 39 people with a severe corner injury and a torn cruciate ligament, 44% had an injury to the nerve that lifts the foot, all with matching bone bruises at the front inner side of the knee. On its own, a lateral collateral ligament (LCL) tear is uncommon, under 2% of knee injuries.
Both cruciate ligaments, when the knee dislocates: one type of dislocation usually comes from extreme hyperextension.

Sources 1, 2, 3, 4, 5, 6, 7, 8, 9

The emergency: a dislocated kneeEmerging evidence

After a knee dislocation, the artery behind the knee is injured in about 18% of cases on average, and 27% of people with an injured artery still had a pulse that could be felt at first. A nerve is injured in about 19%, mostly the one that lifts the foot. That's why a deformed knee, a cold, pale or numb foot, or a knee that felt as if it came out after a high-energy injury is a 999 call, even if a pulse can be felt.

Sources 9, 10

Sprains and bone bruises

An injury can range from a mild sprain to torn ligaments, which is why the warning signs matter. At the milder end, pain at the back of the knee and a pinch at the front are typical. The NHS says most sprains feel better after 2 weeks, that strenuous exercise such as running should wait up to 8 weeks, and that severe sprains can take months to get back to normal.

Bone bruises seen on MRI fade over months: those with a tear of the inner knee ligament (the medial collateral ligament, or MCL) may heal in 2 to 4 months, those with an ACL tear more slowly (a median of 3 months on the thigh bone and 6 on the shin bone), and 95% of bruises without damage to the bone surface resolve. Their long-term course is poorly studied.

Sources 10, 2

X-ray or not: the Ottawa knee ruleStrong evidence

Clinicians use the Ottawa knee rule: an X-ray is needed if you are 55 or over, the bony bump on the outer side just below the knee (the head of the fibula) is tender, only the kneecap is tender, you can't bend the knee to 90°, or you couldn't take 4 steps both straight after the injury and in the clinic. It identified every fracture when it was tested, and 98.5% across 6 studies of 4,249 adults.

Ligaments and bone bruises don't show on X-rays. MRI shows them when the examination suggests a scan is needed.

Sources 11, 12, 13

When an injury is missedEmerging evidence

In 12 young people (median age 18.5) who still had pain and couldn't get back to sport after a hyperextension, earlier MRI scans hadn't explained it. Examining the knee near straight showed extra backward bending and a backward sag of the shin, from an injury to one bundle of the PCL. Pain, or a feeling that the knee goes back too far, weeks after a hyperextension is a reason for a specialist examination rather than another scan (our reading).

Source 14

Knees that bend back naturally

Most knees straighten slightly past 0°, and doctors call a knee that bends back further genu recurvatum. In a US reference study of 674 healthy people aged 2 to 69, knees went past straight by 5.4° on average in girls and 1.6° in boys aged 2 to 8, falling to 1.2° in women and 0.5° in men aged 45 to 69. Girls and women were more mobile in nearly every joint, and range fell with age.

A knee that bends back more than 10° scores a point on the 9-point Beighton score for general hypermobility (5 or more suggests it in adults, 6 in children before puberty, 4 over 50). It's common in dancers: 72% of 85 elite Australian dancers met the cut-off. Children become less bendy as they grow: in 126 children aged 6 to 11 followed for 2 years, the share with the highest scores fell from 25% to 6%. The NHS says joint hypermobility syndrome mostly affects children and young people and often gets better with age.

Sources 15, 16, 17, 18, 19, 20

After a stroke: a different problem

A knee that snaps back while walking after a stroke is common (reported in 19.5% to 65% of people who walk unaided) and comes from weakness, tight calf and thigh muscles and poor joint sense. It's managed with braces, electrical stimulation and walking practice, led by a physiotherapist or orthotist. Cerebral palsy and polio can do the same. This guide's plan isn't for it.

Source 21

What helps, and how strong the evidence is

First, find out what was injuredEmerging evidence

No trial has studied hyperextension injuries as a group: care follows whatever was damaged. A torn ACL, PCL or outer corner follows its own guide, a dislocated knee is an emergency, and a bone bruise or a sprain at the back of the knee is managed like other knee sprains, which is what this guide's plan is for.

Sources 10, 9, 5, 3

A sprain: the NHS's first days, then movement and strengthEmerging evidence

For the first 2 to 3 days, the NHS advises protecting the knee, resting it, ice for up to 20 minutes every 2 to 3 hours, a bandage for support and raising it on a pillow; after that, keep it moving. No trial has tested rehab after a hyperextension sprain, so the plan borrows its doses from an NHS trust's leaflet for knee ligament injuries: movement exercises 2 to 3 times a day, and strength work of 3 sets of 8 to 12, 2 to 3 times a week with a rest day between.

It changes one thing on purpose: the knee is never forced back past straight in the first weeks. That's our adaptation, in line with our PCL guide.

Sources 10, 22

Natural hyperextension and ACL tears: the studies disagreeMixed evidence

Three case-control studies, which compare injured athletes with uninjured ones, found a link. In 20 injured and 20 uninjured female athletes, knees that bent back helped tell the groups apart. Among 1,558 screened female footballers and basketball players, knees that bent back went with 5 times the odds of being one of the 19 who later tore an ACL, compared with matched teammates. And 79% of 169 people having ACL reconstruction had knees that bent back, against 37% of 65 people without an injury.

But in a 4.5-year prospective study of 287 female team-sport athletes (23 ACL tears), knee hyperextension, hypermobility and knee looseness weren't linked with ACL injury. And in 1,250 children and teenagers having ACL reconstruction, about half with knees that bent back, it made no difference to looseness, function or repeat surgery. Knees that bend back aren't a reason to stop sport.

Sources 23, 24, 25, 26, 27

Knees that bend back with symptoms: strength and controlEmerging evidence

Painless knees that bend back need no treatment. When they come with pain, sprains, kneecaps that slip or a knee that gives way, the NHS's main treatment for joint hypermobility syndrome is improving muscle strength and fitness so the joints are better protected, starting with low-impact exercise, and it advises: 'do not overextend your joints just because you can'.

The knee-specific evidence is small but positive. In 18 people with joint hypermobility syndrome, 8 weeks of exercise with the feet on the floor improved knee joint sense in 16, with symptoms easing. In 40 people, the 15 given 8 weeks of joint-sense exercise had less pain and better function than the 25 who weren't.

Sources 20, 28, 29

How much pain is OK while you exercise?

After an injury, 0 to 3 out of 10 and watch the swelling (borrowed)Emerging evidence

After an injury: an NHS trust's knee ligament leaflet says to keep pain between 0 and 3 out of 10, and that pain above that usually means you're doing too much, so reduce the repetitions or the load. It's the same rule as our ACL guide's, borrowed here because no rule has been tested after a hyperextension.

Measure round the middle of both knees with a soft tape. If the injured knee is more than 1 cm bigger, you've done too much: let it settle first. Some soreness the next day is fine, but more pain or swelling means don't push the exercises as far.

Knees that bend back, without an injury: aim for muscle effort without joint pain. Sore muscles for a day or two are normal at first; sharp joint pain, pain in new places or a joint that feels about to slip are not, so make the move smaller or drop back (the tips from our hypermobility routine).

The knee giving way, bending further back than before, or new swelling isn't part of the rule: stop and get it checked.

Sources 22, 10

The exercise plan: 4 stages

Start at the first stage. Each move opens a full guide with a 3D demo.

Stage 1

Protect and settle (about days 0 to 14)

For 2 to 3 days: protect, rest, ice for up to 20 minutes every 2 to 3 hours, support with a bandage and raise the leg, then keep it moving (NHS advice). Walk as normally as you can, with crutches if you need them. Move the knee little and often, but don't force it past straight: no knee hangs or stretches that push it back yet.

Quad set (static quads) demonstrated on the 3D figure

3D demoQuad set (static quads)Beginner · No equipment

Hold 10 s, 10 times, 2 to 3 times a day · Tighten to straight without pushing the knee back. Editorial dose

Harder: Straight-leg raise

Supine heel slide demonstrated on the 3D figure

3D demoSupine heel slideBeginner · No equipment

10 to 20 times, holding 10 s, 2 to 3 times a day · Bend as far as is comfortable. The NHS trust leaflet's dose

Harder: Hip windshield wipers

Straight-leg raise demonstrated on the 3D figure

3D demoStraight-leg raiseBeginner · No equipment

2 to 3 sets of 10 · Once you can tighten the thigh fully. Editorial dose

Easier: Quad set (static quads) · Harder: Leg extension

Ankle circles demonstrated on the 3D figure

3D demoAnkle circlesBeginner · No equipment

10 slow circles each way, little and often · Helps the swelling. The move page's dose

Harder: Ankle CARs (controlled articular rotations)

Glute bridge demonstrated on the 3D figure

3D demoGlute bridgeBeginner · No equipment

2 sets of 10 · Editorial dose

Easier: Pelvic tilt into bridge · Harder: Glute kickback (quadruped hip extension)

Stationary cycling demonstrated on the 3D figure

3D demoStationary cyclingBeginner · Cardio machine

10 to 15 min, easy · Once the knee bends far enough to pedal round. Editorial

Harder: Air bike intervals

Move on when: You walk without a limp, the injured knee is no more than 1 cm bigger round the middle than the other, and it bends fully and straightens to its usual point.

Follow along: a timer, a cue and the next move, one step at a time.

Stage 2

Strength in the middle of the range (about weeks 2 to 6)

3 sets of 8 to 12, 2 to 3 times a week with a rest day between, leaving 2 to 4 repetitions in the tank: the NHS trust leaflet's dose. Finish each repetition at soft knees, never snapping into lockout. Hamstring curls wait until a PCL injury has been ruled out, because resisted hamstring work is delayed after one.

Sit to stand from a chair demonstrated on the 3D figure

3D demoSit to stand from a chairBeginner · A bench or box

3 sets of 8 to 12 · The leaflet's dose

Harder: Bodyweight squat

3D demoStep-upBeginner · A step

3 sets of 8 to 12 each leg · A soft knee at the top. The leaflet's dose

Easier: Low step-up · Harder: Dumbbell step-up

3D demoLeg pressBeginner · Strength machine

3 sets of 8 to 12 · Stop just short of straight. The leaflet's dose

Harder: Bodyweight squat

3D demoWall sitBeginner · A wall

3 to 4 holds of 20 to 40 s · Editorial dose

Easier: Straight-leg raise · Harder: Spanish squat (band squat hold)

Standing hamstring curl demonstrated on the 3D figure

3D demoStanding hamstring curlBeginner · A wall

3 sets of 10, holding 5 s at the top · Only once a PCL injury has been ruled out. The move page's dose

Harder: Slider hamstring curl

Single-leg stand demonstrated on the 3D figure

3D demoSingle-leg standBeginner · A wall

Build to 30 to 60 s each leg · Standing knee soft. The knee hub's dose

Easier: Tandem stance and heel-to-toe walk · Harder: Single-leg reach matrix

Move on when: The strength work stays at 0 to 3 out of 10 with no rise in swelling the next day, you walk briskly, and the knee doesn't feel as if it will go back.

Follow along: a timer, a cue and the next move, one step at a time.

Stage 3

Land, run and return (from about week 6)

Landing and single-leg control, then running and sport. The NHS says strenuous exercise such as running should wait up to 8 weeks after a sprain. Doses are editorial unless named.

Snapdown to athletic landing demonstrated on the 3D figure

3D demoSnapdown to athletic landingBeginner · No equipment

2 to 3 sets of 5 · Land on soft knees

Harder: Box drop landing

Split squat demonstrated on the 3D figure

3D demoSplit squatIntermediate · No equipment

3 sets of 8 to 12 each leg · The leaflet's dose

Easier: Bodyweight squat · Harder: Reverse lunge

Single-leg Romanian deadlift demonstrated on the 3D figure

3D demoSingle-leg Romanian deadliftAdvanced · A dumbbell

3 sets of 8 each leg · Fingertips on a wall at first

Easier: Dumbbell Romanian deadlift

Single-leg hop and stick demonstrated on the 3D figure

3D demoSingle-leg hop and stickIntermediate · No equipment

3 sets of 5 each leg · Forwards first

Easier: Standing broad jump with stuck landing · Harder: Alternate-leg bounding

Treadmill jogging demonstrated on the 3D figure

3D demoTreadmill joggingIntermediate · Cardio machine

Walk-jog intervals, then continuous running

Easier: Treadmill walking · Harder: Sprint intervals

Shuttle runs demonstrated on the 3D figure

3D demoShuttle runsAdvanced · No equipment

4 to 6 runs, wide turns first

Easier: Treadmill jogging

Move on when: Full training without pain above 3 out of 10, new swelling or the knee giving way. Keep a warm-up such as the knee control warm-up going.

Follow along: a timer, a cue and the next move, one step at a time.

Stage 4

Control the last few degrees (after an injury, or for knees that bend back naturally)

Strength and control in the middle of the range, and standing and landing on soft knees, 2 to 3 times a week. Start low and go slow. The NHS advice for bendy joints: 'do not overextend your joints just because you can'. Our hypermobility routine covers the rest of the body.

3D demoSingle-leg standBeginner · A wall

2 holds of 20 s each leg, building to 3 holds of 30 to 60 s · Standing knee soft. The hypermobility routine's dose, then the knee hub's

Easier: Tandem stance and heel-to-toe walk · Harder: Single-leg reach matrix

Low step-up demonstrated on the 3D figure

3D demoLow step-upBeginner · A step

6 each leg, building to 3 sets of 10 · Knee over the middle of the foot. The hypermobility routine's starting dose; the build is editorial

Harder: Step-up

3D demoSit to stand from a chairBeginner · A bench or box

8, building to 3 sets of 10 · The hypermobility routine's starting dose; the build is editorial

Harder: Bodyweight squat

3D demoGlute bridgeBeginner · No equipment

10, with a 2-second squeeze · The hypermobility routine's dose

Easier: Pelvic tilt into bridge · Harder: Glute kickback (quadruped hip extension)

Slow calf raise demonstrated on the 3D figure

3D demoSlow calf raiseBeginner · A wall

3 sets of 12 · Editorial dose

Easier: Seated bent-knee calf raise (soleus raise) · Harder: Standing dumbbell calf raise

3D demoStanding hamstring curlBeginner · A wall

3 sets of 10 · Once any PCL injury has been ruled out or cleared. The move page's dose

Harder: Slider hamstring curl

Move on when: This is a keep-it-going stage: add a few repetitions before adding load, and change one thing every 1 to 2 weeks (the hypermobility routine's tips).

Follow along: a timer, a cue and the next move, one step at a time.

What to change for now

If a ligament is torn

This plan is for a sprain or bone bruise, once a broken bone, a dislocation and a ligament tear needing specialist care have been ruled out. If a ligament is torn, follow our ACL, PCL or LCL guide and your team's plan instead.

Sources 5, 3, 8

Don't force the knee back for now

Exercises that push the knee fully straight, such as heel hangs and lying face down with the lower leg hanging off a bed (both in that ACL leaflet), and stretches that force the knee back, wait until the injured structures have settled. Let the knee straighten to its usual point on its own (our adaptation).

Source 22

Standing with soft knees

For knees that bend back, and after an injury, standing with the knees very slightly unlocked is the practical version of the NHS advice not to overextend your joints. The steps are our suggestion.

1. Stand with your feet hip-width apart and your weight spread across the whole foot.
2. Notice whether your knees are pushed back as far as they will go.
3. Unlock them very slightly: a millimetre or two, not a bend anyone could see.
4. Feel the front of the thigh switch on gently, and keep breathing.
5. Practise for a minute at a time when you're standing still, such as in a queue or at the cooker.
6. If you feel faint while standing, cross your legs or rock up and down on your toes, as the NHS advises.

Sources 20, 30

Braces

For a minor sprain, a bandage or support for the first few days is part of the NHS's advice, but we found no trial of hinged or hyperextension-blocking braces after a hyperextension. After a ligament injury, wear a brace only if your team gives you one. For knees that bend back naturally, the NHS's treatment is strength and fitness, not a brace.

Sources 10, 20

Sport, dance and gymnastics

Knees that bend back aren't a reason to stop sport. A warm-up that trains landing and cutting control, such as our knee control warm-up, suits everyone (our suggestion). Dancers and gymnasts: avoid hanging on the end of your range in standing positions, and keep a slight bend in the standing knee.

Sources 26, 20

Positions to swap, and why

Habit or position	Why it matters	Instead
Ignoring a pop, quick swelling or a knee that gives way	They point to a torn ligament that needs assessing.	Get it checked the same or the next day.
Ignoring numbness, a cold or pale foot, or a knee that looks out of place after a severe injury	The artery and nerve behind the knee can be injured, even with a pulse.	Call 999.
Knee hangs or stretches that force the knee straight in the first weeks	They stretch the structures that were just overstretched.	Gentle heel slides; let the knee straighten to its usual point by itself.Try: Supine heel slide
Hamstring curls before a PCL injury has been ruled out	The hamstrings pull the shin backwards, and PCL rehab delays resisted hamstring work.	Bridges.Try: Glute bridge
Locking out hard on the leg press	The move page's own cue is to press to nearly straight without locking.	Stop just short of straight.Try: Wall sit
Landing from jumps on straight legs	Landing on straight legs is a common way to get injured (our reasoning).	Soft-knee landings.Try: Snapdown to athletic landing
Hanging on the end of your range in standing poses such as the triangle pose	The NHS advice for bendy joints is not to overextend them just because you can.	Keep a slight bend in the front knee, and build strength in the middle of the range.Try: Single-leg stand
Going back to sport by the calendar	Most sprains feel better in 2 weeks, but strenuous exercise can wait up to 8 weeks, and ligament injuries take months.	The stage 3 checks.Try: Single-leg hop and stick
Wearing a brace all day for knees that bend back naturally	There's no evidence it helps painless hyperextension; strength and fitness are the NHS's treatment for hypermobility with symptoms.	The stage 4 strength and control work.Try: Low step-up

Routines to follow

Low-impact leg workout (no jumping)

A gentle leg strength routine with no jumping: sit-to-stands, step-ups, wall sits, bridges and calf raises.

20 minBeginner7 movesA bench or box, A step

Balance exercises routine

Balance practice in 10 minutes: tandem stance, single-leg stands, marches, heel walks, tree pose and floor transfers.

10 minBeginner7 movesA wall, A bench or box

Knee control warm-up

A 20-minute warm-up that trains your knees to track over your toes: side-hip strength, squats and lunges with alignment practice, balance and quiet landings.

20 minBeginner10 movesA wall, A band

Hypermobility exercises: a strength and control routine

A 25-minute low-load routine for hypermobile joints: hip, trunk and shoulder control plus balance, done slowly in the middle of your range.

25 minBeginner15 movesA bench or box, A wall

More moves for this area

Questions people ask

What is a hyperextended knee?

An injury in which the knee is forced backwards past straight, in a fall, tackle or bad landing. It ranges from a mild sprain at the back of the knee or a bone bruise to torn ligaments, which is why the warning signs come first.

How do I know if it's serious?

A pop, the whole knee swelling within hours, or a knee that gives way or bends back further than the other needs checking the same or next day. A knee that looks out of place, or a numb, cold or pale foot after a severe injury, is a 999 call.

How long does a hyperextended knee take to heal?

A mild sprain often feels better within 2 weeks, but the NHS advises avoiding strenuous exercise such as running for up to 8 weeks, and bone bruises can take months to fade on scans. Torn ligaments take months, and their guides set out the stages.

Can I walk on it?

Usually, if it's a sprain: use crutches at first if you limp. If you can't put weight on it or take 4 steps, get it checked the same day.

Did I tear my ACL or PCL?

You can't tell for certain at home. A pop, swelling within a day and a knee that gives way suggest the ACL; the PCL can also tear when the knee goes back, with pain, swelling, stiffness and a feeling it may give way. A clinician's examination decides, sometimes with an MRI.

Why does the back of my knee hurt?

The back of the joint capsule and the structures behind the knee are stretched when it bends back. Pain at the front can come from the bones being squashed together.

What is a bone bruise?

Bleeding and swelling inside the bone where the bones were squashed together. It shows on an MRI but not on an X-ray, and most settle over a few months.

What exercises help?

Gentle bending and thigh tightening at first, then strength in the middle of the range, then landing and running, without forcing the knee back. If a ligament is torn, follow that ligament's guide.

Should I wear a knee brace?

My knees bend backwards when I stand. Is that bad?

Usually not: most knees go slightly past straight, more in children and women, and more than 10° is one sign of general hypermobility. It matters if it comes with pain, sprains or knees that give way, and then strength and control exercises help.

Is it bad to lock your knees?

Not for most people, but the NHS advice for bendy joints is not to overextend them, and reviews of fat pad pain advise avoiding it, so soft knees are a sensible habit if your knees hurt or bend well back. The NHS doesn't list locked knees as a cause of fainting; if you feel faint standing, cross your legs or rock on your toes.

Do knees that bend back mean a higher risk of an ACL tear?

The studies disagree. Three case-control studies found a link, but a 4.5-year study that followed 287 female athletes forward found none. It isn't a reason to stop sport, and a landing and cutting warm-up suits everyone.

Related exercise guides

Other pain guides

Sources

Exercise education, not a diagnosis or treatment plan. It is written from the guidelines and studies listed above; review by a clinician is pending. If your pain follows an injury, is severe, is getting worse, or comes with any warning sign listed on this page, get it assessed. Health disclaimer.