If forward lunges make the front of your knee complain, you are not imagining it. Catching your body weight on a forward step asks a lot of the kneecap joint. The reverse lunge, where the moving leg steps back instead, trains the same muscles with less of that load.
What the biomechanics studies found
A 2021 study in Physical Therapy in Sport measured 20 women without knee pain doing forward and backward lunges to the same depth. The forward lunge produced higher quadriceps force, higher patellofemoral (kneecap) joint force, and a faster loading rate. The backward lunge came with more forward trunk lean, which shifts work toward the hip. The participants were pain-free, so whether people with kneecap pain feel better on the reverse version still needs testing.
Two older findings fit. Escamilla and colleagues (Clinical Biomechanics, 2008) found kneecap compressive force during lunges was lowest between 0 and 50 degrees of knee bend and rose as the knee bent further. Farrokhi and colleagues (JOSPT, 2008) showed that leaning the trunk forward during a lunge increased gluteus maximus and hamstring activity.
Muscles worked
- Quadriceps of the front leg, which control the lowering and drive you up.
- Gluteus maximus and hamstrings of the front leg, more so with a slight forward hinge from the hips.
- Hip flexors of the back leg, which get a stretch at the bottom.
- Calf, foot, and the small hip muscles that keep the pelvis level.
How to do it
- Stand tall, feet hip-width apart. Hold a chair back, counter, or wall with one hand if balance is shaky.
- Step one foot back far enough that both knees can bend toward 90 degrees without the front heel lifting.
- Lower until the back knee hovers above the floor, or as far as is comfortable. Keep the front shin near vertical and the kneecap pointing over the second toe, not drifting inward.
- Keep the trunk upright or hinged slightly forward from the hips, back flat.
- Push through the whole front foot to stand, bring the back foot forward, then switch sides.
Step length and depth
A short step pushes the front knee farther over the toes and bends it more, which raises kneecap load. A longer step keeps the shin more vertical. If your knee is sensitive, a shallower lunge within that 0 to 50 degree range is a sensible start. Your physical therapist can set the step length and depth that suit your knee right now.
Making it harder
- Let go of the support and perform the lunge freestanding.
- Slow the lowering phase to three or four seconds.
- Hold a dumbbell in each hand, or one at the chest in a goblet position.
- Stand the front foot on a low step (a deficit) so the back knee travels lower. Add this only once the flat version is comfortable.
If your plan also includes climbing onto a box, see our guide to step-ups
Who should hold off
Gentler does not mean safe for everyone. If you have a freshly injured or swollen knee, recent knee or hip surgery, or a weight-bearing limit from your surgeon or therapist, wait until they clear you. If balance is a problem, keep a hand on a support.
Muscle effort in the thigh and hip is expected. Sharp pain at the kneecap, pain that climbs during the set, swelling afterwards, or a knee that feels like it may give way are reasons to stop and check with your physical therapist or doctor before continuing.
Doing this exercise in a guided session
The cues that matter most here, front knee over the foot and shin near vertical, are hard to judge from inside the movement. In a KineTrue camera-guided session the app gives feedback on those positions as you move and records the reps and depth completed, so your therapist can see how the exercise is going between visits and adjust step length, depth, or load.