Stiff-Leg Deadlift vs Romanian Deadlift: What's Actually Different

The main difference is knee bend: stiff-leg deadlifts use nearly straight legs, Romanian deadlifts allow a slight, fixed knee bend

Both are hip-hinge exercises that primarily target the hamstrings and glutes, and both are performed with a relatively straight-leg stance compared to a conventional deadlift. But the small difference in knee bend changes the bar path, the range of motion, and where you feel the stretch most. Neither is "wrong": they're two closely related variations that are each better suited to slightly different goals.

The technical differences

• Knee bend: stiff-leg deadlifts (SLDL) keep the knees nearly locked (a very slight, mostly unchanging bend) throughout the movement. Romanian deadlifts (RDL) start from a standing position with a slight knee bend that's maintained, not increased, as you hinge down.
• Starting position: stiff-leg deadlifts are often performed starting from the floor, picking the bar up at the start of each rep, similar to a conventional deadlift but with straighter legs. Romanian deadlifts are typically performed starting from a standing position with the bar already in hand, lowering it down and back up without the bar touching the floor between reps (though it can touch lightly at the bottom).
• Range of motion: because the knees stay straighter, stiff-leg deadlifts generally don't go as low as Romanian deadlifts before hamstring flexibility limits further hip hinge, RDLs usually get the hips further back and the torso closer to parallel with the floor since the slight knee bend allows a bit more travel.
• Bar path: both exercises should keep the bar close to the legs throughout, but the straighter-leg stiff-leg deadlift often has a slightly more vertical bar path near the floor, while the Romanian deadlift's bar path curves more around the knees as they bend slightly.
• Where you feel it: stiff-leg deadlifts tend to produce more hamstring stretch and lower back involvement because of the reduced knee bend and (often) the dead-stop start from the floor. Romanian deadlifts tend to feel more glute-and-hamstring focused with slightly less lower back strain for most lifters, because the knee bend takes a bit of tension off the hamstrings at a given depth.

Which to choose: hamstring vs lower-back emphasis

If your primary goal is maximizing hamstring stretch and development, the stiff-leg deadlift's straighter-knee position tends to put more direct tension on the hamstrings through a slightly more limited but more stretch-focused range. If you want a movement that trains the full posterior chain (hamstrings, glutes, and some lower back) with typically better control and a bit more range of motion, the Romanian deadlift is usually the more commonly recommended default, especially for lifters newer to hip-hinge patterns.

People with lower back sensitivity often find Romanian deadlifts more manageable than stiff-leg deadlifts, since the slight knee bend and standing start reduce how much the lower back has to work to control the hinge, especially compared to pulling from a dead stop on the floor.

How to perform each one with good form

• Stiff-leg deadlift setup: stand with the bar over the middle of your feet, hinge at the hips with a very slight, fixed knee bend, keep the bar close to your shins as you lower it toward the floor, and stop at the point where your lower back would otherwise start to round. Drive your hips forward to return to standing.
• Romanian deadlift setup: start standing with the bar at hip height and a slight knee bend already set, push your hips back while keeping the knee bend roughly constant, let the bar slide down close to your thighs and shins, and stop once you feel a strong hamstring stretch or your lower back would otherwise round. Reverse the motion by driving the hips forward.

Common form mistakes for each

• Stiff-leg deadlift, locking the knees completely: "stiff-leg" doesn't mean rigidly locked; a hard lockout increases strain on the knee joint and hamstring attachment. Keep a very slight, soft bend.
• Stiff-leg deadlift, rounding the lower back to reach the floor: if your hamstring flexibility doesn't allow you to reach the bar on the floor with a flat back, it's better to use blocks/a rack to raise the starting height, or switch to the Romanian variation, than to round the spine to get there.
• Romanian deadlift, bending the knees more as you descend: the knee bend should be set near the top and held roughly constant; actively bending the knees further as you lower the bar turns it into a regular deadlift or squat-like pattern and takes tension off the hamstrings.
• Romanian deadlift, letting the bar drift away from the legs: the bar should stay close to the thighs and shins throughout; drifting forward increases lower back strain and reduces control.
• Both, hinging from the lower back instead of the hips: the movement should come from folding at the hip joint with a neutral spine, not from rounding or arching through the lumbar spine.
• Both, going heavier than your current hamstring flexibility allows: loading up weight before you have the mobility to maintain a flat back through a full range encourages compensation through the lower back. It's better to use a shorter range of motion with good form and build flexibility over time than to force depth.

Programming notes

Both variations are commonly used as secondary or accessory hip-hinge movements, often placed after a primary lift like a conventional deadlift or squat, since they're less demanding to set up and recover from per session than a maximal deadlift. A typical rep range for either is 6-12 reps per set, with lighter loads and more careful attention to range of motion when first learning either pattern, especially for the straighter-leg stiff-leg version.

Which one should you actually program?

For most lifters, especially those newer to hip-hinge movements, starting with the Romanian deadlift is the more practical choice: the standing start is simpler to set up for each rep, the slight knee bend is generally easier on the lower back, and it still builds substantial hamstring and glute strength. Once that pattern feels solid and controlled, adding the stiff-leg deadlift as a second hamstring-focused exercise, perhaps on a different day or as a secondary movement in the same session, is a reasonable way to get the extra hamstring stretch emphasis without replacing the RDL outright.

Neither exercise needs to be maxed out for strength the way a conventional deadlift might be; both are commonly used at lighter relative loads with a focus on feeling the target muscles work through a full, controlled range rather than moving the heaviest weight possible.

Warming up before either variation

Because both exercises ask the hamstrings to lengthen under tension, a brief warm-up that includes some lighter hip-hinge reps and dynamic hamstring movement (such as controlled leg swings) is a sensible way to prepare the tissue before loading up, particularly for the stiff-leg version where the knee stays straighter and the hamstring is placed under a slightly longer stretch for a given depth.

Grip and bar control also matter for both exercises: a double-overhand grip is fine for lighter sets, but as the load increases, many lifters switch to a mixed or hook grip to keep the bar from sliding out of their hands before the target muscles have been pushed to fatigue, since the hamstrings and glutes, not the grip, should be the limiting factor in either lift.