Stop the Ache: 5 Common Causes of Knee Pain During Workouts (and How to Fix Them)

Few things derail a training routine faster than knee pain during workouts. That nagging ache when you squat, run or climb stairs is incredibly common — and the good news is that it's usually fixable. In most cases the knee is simply the messenger: the real problem lies in the muscles, mechanics or training habits around it.

Below are five of the most common causes of exercise-related knee pain and a practical fix for each. This is general educational information rather than medical advice, so if your pain is severe, persistent or came from a specific injury, see a doctor or physiotherapist before working through it.

Why do your knees hurt during workouts?

The most common form of exercise-related knee pain is patellofemoral pain — often called "runner's knee" — an ache around or behind the kneecap that worsens with loaded bending like squatting, running or descending stairs. It happens when stress is unevenly distributed under the kneecap, and that uneven load usually traces back to the wider "kinetic chain" of the hip, thigh and foot rather than the knee joint itself.

According to a clinical overview in StatPearls, the large majority of cases respond well to conservative measures — strengthening, mobility work and sensible load management — without any need for surgery. That's why the five fixes below focus on what's happening around the knee.

1Weak hips and glutes

This is the big one. When the muscles on the side of your hip — the glutes and hip abductors — are weak, they can't keep your thigh aligned under load. The knee then drifts inward (a movement called valgus) every time you squat, lunge or land, concentrating stress on the inner kneecap.

The evidence here is strong: a cross-sectional study of runners with patellofemoral pain found their hip abduction and knee-extensor strength was significantly lower than in pain-free runners. Strengthening the hips reduces that inward collapse and takes load off the knee.

2Tight quads, IT band and hip flexors

Tightness is the flip side of weakness. When the quadriceps, iliotibial (IT) band or hip flexors become stiff, they pull on the kneecap and alter how it tracks in its groove. A review of common knee injuries in runners notes that reduced flexibility in these structures increases compression of the kneecap against the thigh bone, which shows up as pain during loaded movement.

3Doing too much, too soon

Sometimes the tissue is fine and the problem is the training plan. Ramping up mileage, weight or session frequency faster than your knees can adapt is a classic trigger for overuse pain. Tendons and cartilage adapt more slowly than your enthusiasm, and sudden spikes in load are a leading cause of anterior knee pain.

4Poor form and technique

Even with strong, mobile muscles, sloppy technique can overload the knee. The most common fault is letting the knees cave inward during squats, lunges and step-downs, or letting the knee travel far past the toes on a single leg. Both shift stress onto the kneecap rep after rep.

5Worn-out or wrong footwear

What's under your feet changes what happens at your knees. Old, broken-down shoes lose their cushioning and support, and footwear that doesn't suit your foot mechanics — for example, excessive inward rolling of the foot — can alter alignment all the way up the chain and increase knee stress during running and jumping.

Managing symptoms while you fix the cause

While you address the underlying issue, a few things can keep you comfortable and training. Warming up thoroughly, reducing painful ranges temporarily, and applying the load-management principles above all help. Some people also find a compression sleeve useful during sessions.

A knee compression sleeve can add warmth, mild support and a better sense of joint position, which some people find reassuring during workouts. Just remember it manages symptoms rather than the root cause — the fixes above are what create lasting change.

Putting it together

Most workout knee pain comes down to a fixable combination of weakness, tightness, load and technique — rarely the knee alone. Work through the five causes above, change one thing at a time, and give each adjustment a couple of weeks to take effect. Keeping a simple record of what you did and how your knee felt makes the pattern obvious, so you can tell which fix is actually working. Health Mentor AI can help you log your workouts and symptoms together and spot those trends. For building the kind of consistent routine that lets these fixes stick, our guide to systems that make fitness automatic is a useful companion.