Knee Pain from Leg Extensions: My Experience

Knee pain and the worst leg extension machine ever!

I’m dating myself a little, but I remember when leg extension and leg curl machines had the arm bar in the middle of the foot/ankle pad. It made complete sense to me. It evenly distributed the load, and the pad had little potential to bend over time.

For the past decade or two, a popular version of the leg extension where the lever arm is placed to one side of the foot/ankle pad. This was made (I believe) for ease of use–you can more easily get in and out of the machine by just sliding into one side.

Great idea, but I’ve run into a problem. Since the lever bar is on one side, it tends to bend over time. One leg will extend further than the other. No big deal, right?

Not really. Over said time, as the bar begins to bend and you slowly change the stress for each knee, a strength imbalance starts to happen. With the imbalance comes pain. And pain signals damage to your knees.

This is exactly what happened to my poor, hurt knees. Over time, the strength imbalance has not only been affected by the leg extension machine, but the pain has translated over to other lower body exercises. In other words, I created a strength and stability imbalance in one exercise, and now everything suffers. Squats and leg presses started to hurt. I started to get majorly frustrated.

For a while, I couldn’t figure things out. Was I just getting older and my knees are starting to crap out? What was the culprit?

I immediately stopped performing any leg machine exercises. I needed to wipe the slate clean and do some process of elimination.

I was suffering from knee pain, specifically in the patellar tendon area. And since tendons have little blood flow as compared to muscle tissue, it would take a while to heal up. In the meantime, I stuck to squats.

Why squats? Because they allow me to freely adjust my ankles, knees, and hips as needed. I’m not locked into a steel machine potentially working against my joints. I can bring my hips back further, adjust my knee flexion, and adjust the angle on my ankles without too much of a fight.

I can tailor a squat to my body type.

Over time, much of the pain went away, and I started to experiment with the leg press once again with success. After much thought, I believe the culprit to be the bend in the foot pad, creating a strength and stability imbalance, thus filling my knees with pain.

Is the leg extension (specifically this design) a bad thing? Not entirely.

From now on, if I’m to use one of these lopsided editions, I’ll be performing unilateral sets–one leg at a time.

Have you experienced similar effects?

Happy lifting!