Knee pain is one of the most common complaints among gym-goers and everyday people alike. Whether it’s from an old injury, joint wear and tear, or simply discomfort during daily movement, weak muscles around the knee can make things worse. But there's a simple exercise that many lifters overlook.
So many people assume that squats and lunges are the best way to build knee strength, and those can contribute to a healthy knee joint. But there’s another exercise that is often overlooked, one that plays a crucial role in knee stability and rehabilitation: the leg extension.
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How Leg Extensions Support Knee Health
Leg extensions primarily target the quadriceps, the muscles at the front of the thigh. These muscles play a direct role in stabilizing the knee joint, helping to absorb impact and control movement. When the quads are weak, the knee can become unstable, leading to improper movement patterns and increased stress on the joint. Strengthening these muscles can provide better support for the knee, reducing strain and lowering the risk of pain or injury.
This is particularly important for people recovering from knee injuries, including ACL tears, patellar tendonitis, and general knee instability. Many physical therapists incorporate leg extensions into rehab programs because they allow for isolated strengthening of the quads without placing excessive strain on other parts of the leg.
And it also works for lifters who experience knee pain during squats. That's because leg extensions help develop the knee joint. And unlike squats or lunges, which require multiple joints to work together, leg extensions focus purely on knee extension, making them a great tool for rebuilding strength in a controlled way.
And here's the science: Leg extensions specifically target the quadriceps, one of the largest muscle groups in the body. By isolating these muscles, leg extensions contribute to increased muscle fiber recruitment and hypertrophy (muscle growth).
When performed with progressive resistance, the exercise stimulates muscle protein synthesis, leading to greater skeletal muscle mass in the quadriceps over time. And according to a 2013 study, more skeletal muscle mass is associated with better performance for powerlifters.
Considered another way, this increase in muscle not only improves knee stability and strength but also contributes to better balance, endurance, and overall lower-body function.
For individuals recovering from injury or experiencing muscle atrophy due to inactivity, leg extensions can be an effective way to regain lost muscle mass in a controlled, low-impact manner. Since they allow for targeted strengthening without requiring full-body coordination like squats or lunges, they are often used in rehab settings to rebuild strength safely and efficiently.
Why Leg Extensions Get a Bad Reputation
Despite their benefits, leg extensions often get criticized, especially in the strength training world. Some argue that they place too much stress on the knee joint, particularly when performed with excessive weight or poor form. While it’s true that improper use of the leg extension machine can cause discomfort or strain, when done correctly, they are a safe and effective way to strengthen the knee-supporting muscles.
The key is to use moderate weight and controlled movements. Avoid locking out the knee at the top of the movement and focus on a slow, controlled contraction of the quadriceps. If discomfort occurs, adjusting the seat position or reducing the range of motion can help make the exercise more comfortable while still providing the strengthening benefits.
How to Incorporate Leg Extensions Into a Knee Health Routine
You can find what you need to do leg extensions in just about any major gym chain. We've seen leg machines at Planet Fitness, LA Fitness, Equinox, and other top gyms. And if you're looking to improve strength at home, it's not hard to find a machine to help. The Rogue glute-ham developer is one option we've tested and liked.
For those dealing with knee pain or looking to build strength and prevent injuries, adding leg extensions to a workout routine can be beneficial. Start with light weight and higher repetitions, such as three sets of 12 to 15 reps, to focus on endurance and control. Over time, as strength improves, resistance can be gradually increased to continue challenging the muscles without overloading the knee joint.
Pairing leg extensions with other knee-friendly exercises, like seated hamstring curls, step-ups, and glute bridges, can help create a balanced approach to strengthening the entire leg. Keeping proper mobility and flexibility in the hamstrings and calves also plays a role in supporting knee health, so incorporating stretching and foam rolling can further reduce discomfort. And don't forget knee sleeves and knee wraps.
Knee pain doesn’t have to mean avoiding the gym or skipping leg day. While squats and lunges are valuable exercises, they aren’t always the best choice for targeted knee strengthening, especially during rehab. Leg extensions, when done properly, can be a key tool in building stronger, more stable knees, helping to reduce pain and improve movement over time.
For those struggling with knee discomfort, it’s worth giving this simple but effective exercise another look. With the right approach, it could be the missing piece in achieving healthier, pain-free knees.
Related Reading: 14 Exercises for a Push Day Workout
