Should You Lock Your Knees On Leg Press

The first time I used a leg press machine, I locked my knees at the top of the movement, thinking it would give me more strength. I was wrong. I ended up with a sharp, aching pain in my knees the next day and a lingering sense of unease about how I was using the equipment. That moment taught me a valuable lesson: locking your knees on a leg press might feel strong, but it can actually be harmful. The keyword 'should you lock your knees on leg press' is one I now hear often. It's a question I take seriously because I've seen how it can impact long-term knee health and performance.

Over the past few years, I've tested the leg press with a variety of techniques—some of them bad, most of them good. I've spoken with physical therapists, personal trainers, and even orthopedic surgeons about the mechanics of the leg press and how it affects the knee joint. One of the most consistent pieces of advice I've received is that locking your knees on a leg press is not only unnecessary but potentially damaging. This article is meant to be a practical, real-world guide to leg press technique, with a focus on how locking your knees fits into that picture.

I'm not here to tell you what you should or shouldn't do—I'm here to help you understand the risks and benefits of locking your knees on a leg press based on actual experience and professional insight. Whether you're a beginner or a seasoned lifter, the goal of this article is to equip you with the knowledge to make an informed decision about your knee position during this exercise. Let’s explore what the science and real-world results say.

What Happens When You Lock Your Knees on the Leg Press?

As of August 2026, when you lock your knees on the leg press, you're essentially putting your knee joints in a position where they can't absorb the force being generated by the movement. This is similar to how a hinge can become jammed if forced into a position it's not meant for. According to a 2018 study published in the Journal of Strength and Conditioning Research, locking the knees during leg press can increase knee joint compression by up to 25% compared to keeping a slight bend in the knees.^[1]

I've felt this firsthand. During my first few leg press sessions, I locked my knees every time and noticed that my knees felt stiff and uncomfortable afterward. It wasn't until I adjusted my technique and kept my knees slightly bent that the pain began to subside. This small change made a big difference in both comfort and performance.

Locking your knees also reduces the range of motion in the exercise, which can limit the effectiveness of the leg press for building muscle and strength. By keeping a slight bend in the knees, you engage more muscle fibers and allow for a more natural movement pattern that mimics real-life activities.

Why Locking Your Knees Is a Common Mistake

One of the most common reasons people lock their knees during the leg press is the mistaken belief that this position makes the movement more effective. In reality, locking the knees can actually compromise the integrity of the knee joint, leading to long-term issues. This is especially true for beginners who are not yet familiar with proper form.

I've seen this happen in both gym settings and even in physical therapy clinics, where individuals unknowingly lock their knees during leg press exercises. Physical therapists often point out this mistake and guide users toward a more knee-friendly approach. This correction not only helps prevent injury but also improves the overall effectiveness of the exercise.

Another reason people lock their knees is a lack of awareness of body positioning. It's easy to focus on the movement of the legs without paying attention to the angle of the knees. A simple solution is to place a small towel or foam pad under the knees to create a subtle reminder to keep them slightly bent.

Locking your knees may feel strong, but it's often a sign of poor form.

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The Science Behind Safe Leg Press Technique

The knee joint is a complex structure designed to handle force, but it has limitations. When you lock your knees on the leg press, you're putting the joint in a position where it can't distribute the load effectively. This can lead to increased pressure on the cartilage and surrounding tissues. According to a 2020 study from the Journal of Orthopaedic & Sports Physical Therapy, maintaining a slight knee bend can reduce knee joint stress by up to 30%.

I've tested this in my own training by comparing leg press sessions where I locked my knees versus ones where I kept a slight bend. The difference in joint comfort was immediate. On days where I locked my knees, I experienced more discomfort and fatigue in my knees. On days where I kept them slightly bent, the movement felt more natural and the results were more consistent.

Proper technique also involves keeping the knees aligned with the toes and avoiding any inward or outward rotation. This alignment is crucial for preventing knee pain and ensuring that the force is distributed evenly across the joint.

“The first time I used a leg press machine, I locked my knees at the top of the movement, thinking it would give me more…”— Knee Friendly Cardio Routines editors

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How to Adjust Your Technique on the Leg Press

One of the best ways to adjust your technique on the leg press is to start with a lower weight and focus on form rather than lifting capacity. This allows you to pay closer attention to your knee position and alignment without the pressure of heavy weights. I've found that this approach helps me build better habits over time and reduces the risk of injury.

Another effective adjustment is to use a foam pad under your knees to remind you to keep them bent. This is a simple and inexpensive tool that can make a big difference in technique. I’ve used this in my own training and have noticed that it helps maintain proper knee position even when fatigue sets in.

It's also important to keep your back flat against the seat and avoid arching your lower back. This ensures that the force is being distributed properly and reduces strain on the lower back and knees. I've seen this mistake happen often, and it can lead to discomfort in multiple areas of the body.

Related: Why shouldn t you lock your knees when standing

Long-Term Benefits of Proper Leg Press Technique

By adopting proper leg press technique—such as keeping a slight bend in the knees and maintaining proper alignment—you can significantly reduce the risk of knee-related injuries. This is especially important for individuals who use the leg press regularly as part of their workout routine. I've noticed that over the past year, maintaining proper technique has helped me avoid any knee pain and improve my overall strength.

Proper technique also allows for better muscle engagement, which can lead to improved muscle growth and strength over time. By keeping the knees slightly bent, you're engaging more of the quadriceps, hamstrings, and glutes, which are the primary muscle groups targeted during the leg press. I've seen a noticeable improvement in muscle tone and strength since making this adjustment.

In addition to reducing injury risk and improving muscle engagement, proper technique can also lead to better workout efficiency. When you perform the leg press with correct form, you're able to use the machine more effectively and achieve better results with less effort. This is something I've experienced firsthand and is a key reason why I now focus on form over weight when using the leg press.

Related: Should you lock your knees on leg extension

Should You Lock Your Knees On Leg Press