One Knee To Chest
Also works: Hamstrings · Lower Back
Lying on your back with one leg flat on the floor and the other hugged toward your nose, this stretch works two joints in opposite directions at once: the bent hip goes into deep flexion for the glute and lower back, while the straight leg's hip flexor is pinned long by the floor. Most people only feel one of those and miss half the drill.
Own the movement
Set up first, then execute. Every cue below is something you can check on your next set.
Before the first rep
- Lie flat on your back on a firm surface, not a soft bed — a mattress lets your pelvis sink and kills the straight-leg half.
- Extend one leg fully along the floor and press the back of that knee down so the hip cannot tuck.
- Grip the bent leg underneath the knee joint, hands behind the thigh, not over the kneecap.
- Let your head and shoulders rest on the floor rather than craning up toward the knee.
Every rep
Breathing & tempo — Breathe slowly through the nose and let the knee travel a centimetre further on each exhale. Never pull harder on an inhale — the brace works against you.
Before you load it
- If pulling the knee in produces a pinch at the front of the hip socket rather than a stretch behind it, stop pulling and take the knee slightly wider. That pinch is bone meeting bone, and forcing it does damage.
How much, how often
Where to start, and what to change when it stops being hard.
No load. Two to three holds of 30 seconds per side. Stretching increases the range you can access; it does not by itself prevent injury, and it will not lengthen tissue permanently from one session. Daily short exposure beats a weekly marathon.
What goes wrong
The errors that show up most often, and the cue that fixes each one.
Pull the bent knee less hard and consciously press the extended heel and knee into the floor. Half the stretch lives in that leg staying down.
Move your hands to the back of the thigh, just above the crease of the knee, and pull the femur rather than the joint.
Rest your skull on the floor and bring the knee to you. If you cannot reach without curling up, loop a towel behind the thigh.
Add a slight pull of the knee across the midline toward the opposite shoulder — that biases the deeper external rotators and usually finds the sensation.
Why bother
Pulling one knee to the chest flexes that hip past what walking ever asks for, which lengthens the gluteus maximus and takes tension off the lumbar erectors on that side. The floor does the other half of the work: it stops the extended leg's pelvis from tipping forward, so the rectus femoris and psoas on that side get held at length instead of escaping into an arched lower back.
Because you are lying down, the spine is unloaded and you cannot cheat with balance or momentum. That makes this one of the few hip stretches that is honest for people with cranky lower backs — there is no hinge to round and no bodyweight pressing through the discs while you hold.
Where it fits
End of a session, or on the floor in the evening. It pairs naturally with deadlift and squat days where the erectors and glutes have taken a beating. Two to three holds of 30 seconds per side, daily if you like — the dose is small enough that frequency costs you nothing.
If this one isn't it
No kit, too hard, or too easy — here's where to go instead.
Same job, different kit
Start here instead
When this gets easy
Asked and answered
Should I do both knees at once instead?
Only if your goal is the lower back. Hugging both knees rounds the lumbar spine and feels pleasant, but it removes the extended leg entirely, so you lose the hip flexor half and the glute stretch is shallower because the pelvis just rolls with you. Do one leg at a time when you want the hip, both when your back is the complaint.
Why do I feel this in my lower back and not my glute?
Usually because your pelvis is rolling off the floor as you pull, so the movement is happening at the lumbar spine instead of the hip. Pull less hard, keep both sit bones on the ground, and steer the knee toward the opposite shoulder. If it still lands in the back, that is the erectors letting go, which is a legitimate result — just not the one advertised.
Is this safe with a disc problem?
It is one of the gentler options because the spine is unloaded and there is no hinge. That said, deep hip flexion does flex the lumbar spine a little, and flexion-sensitive backs sometimes dislike it. Keep the range small, stay off any position that reproduces leg symptoms, and get a clinician to look at it rather than self-prescribing.
How long before I notice more range?
Within a single hold you will move further — that is a nervous system change, and it fades within an hour. Lasting range takes a few weeks of near-daily exposure, and it holds better if you also strengthen the hip through the new range with something like a single-leg glute bridge.