Knee pain during workouts almost always comes down to one of a few common problems: the kneecap tracking poorly against the thighbone, a tendon getting overloaded faster than it can recover, or weakness somewhere else in the leg forcing the knee to absorb stress it wasn’t designed for. The good news is that most exercise-related knee pain isn’t structural damage. It’s a signal that something about your movement, your training volume, or your muscle balance needs adjusting.
Pain at the Front of the Knee
The most common source of workout-related knee pain is patellofemoral pain syndrome, often called runner’s knee. It causes an ache in or around the kneecap that gets worse during any activity where the knee bends under load: squats, lunges, running, stair climbing, and jumping. Sitting for long periods with bent knees can also flare it up, which is why people sometimes notice it at a desk after a morning workout.
The underlying issue is how the kneecap moves. During bending, the kneecap should glide smoothly in a groove on the thighbone. When it shifts slightly off track, often pulling to the outside, it irritates the surrounding tissue. This maltracking tends to get worse under load, which is why a bodyweight squat might feel fine but a heavy squat doesn’t. Weak quadriceps are a significant risk factor because those muscles are responsible for stabilizing the kneecap during movement. When they can’t do their job well enough, the kneecap becomes less stable and more prone to drifting.
Another pattern that contributes is something called dynamic valgus, where the knee collapses inward during a squat, lunge, or landing. This increases the sideways force on the kneecap and worsens that tracking problem. If you’ve ever watched yourself squat in a mirror and noticed your knees caving inward, that’s dynamic valgus, and it’s one of the most fixable causes of front-of-knee pain.
Pain Just Below the Kneecap
If the pain is more focused on the tendon connecting your kneecap to your shinbone, right at the bottom of the kneecap, the likely culprit is patellar tendinitis. This is sometimes called jumper’s knee because it’s most common in sports involving repeated jumping and landing, like basketball and volleyball. But it also shows up in runners and people doing high-rep leg work in the gym.
The mechanism is straightforward: repeated stress on the patellar tendon creates tiny tears faster than the body can repair them. Without adequate rest between sessions, the tendon weakens instead of strengthening. The body responds by thickening the tendon, which can make it stiffer and more painful. The hallmark sign is pain that’s sharp during activity and dull or stiff afterward, particularly when going downstairs or pressing on the tendon itself.
Recovery from patellar tendinitis typically takes about six weeks with proper management, though more severe cases can require several months of rehab. The key is reducing the load on the tendon enough for healing to begin while gradually rebuilding its capacity through controlled exercise.
Pain on the Outside of the Knee
Lateral knee pain, meaning pain on the outer side, often points to iliotibial band syndrome. The iliotibial band is a thick strip of connective tissue running from the hip down the outside of the thigh to just below the knee. When it’s too tight, it rubs against the bony bump on the outside of the knee during every bend-and-straighten cycle. That repeated friction causes inflammation and a burning or aching pain that typically shows up partway through a run or cycling session.
Several things can tighten the IT band: not warming up adequately, pushing through fatigue, running on sloped surfaces, wearing worn-out shoes, or simply ramping up training volume too quickly. Hip abductor weakness is also a common contributor, and it connects to a broader pattern worth understanding.
Your Hips May Be the Real Problem
The knee sits between two powerful joints, the hip and the ankle, and it often pays the price when either one isn’t doing its job. Hip abductor weakness is a particularly common driver of knee pain during workouts. The hip abductors, primarily the gluteus medius on the side of the hip, stabilize the thighbone in the frontal plane during any single-leg movement like walking, running, lunging, or landing from a jump.
When these muscles are weak, the hip tends to drop or rotate inward during weight-bearing activities. That inward collapse changes the angle at the knee, increasing stress on both the kneecap and the outer knee structures. It’s the same dynamic valgus pattern mentioned earlier, and it’s a factor in patellofemoral pain, IT band syndrome, and even some meniscus injuries. This is why many physical therapy programs for knee pain focus heavily on hip and glute strengthening rather than just targeting the knee itself.
If you spend most of your day sitting, your hip abductors are likely underactive. Exercises like side-lying leg raises, clamshells, banded lateral walks, and single-leg glute bridges can build the stability your knees need.
Signs of Something More Serious
Most workout-related knee pain is an overuse or biomechanical issue, not a structural injury. But certain symptoms suggest something beyond routine strain. A meniscus tear, for example, involves the rubbery cartilage pads inside the knee joint. It can feel different from overuse pain in several ways: there’s often a popping sensation at the time of injury, swelling that develops over 24 hours or more, difficulty fully straightening the knee, or a sensation of the knee locking or catching during movement. You might also feel like the knee could give way under you.
Seek urgent care if your knee is visibly deformed, you heard a pop during the injury, you can’t bear weight on it, or it swelled suddenly. Schedule an appointment if the joint is persistently swollen, red, warm to the touch, or painful enough to interfere with sleep or daily activities. A fever alongside knee pain can signal an infection that needs prompt treatment.
Common Workout Mistakes That Cause Knee Pain
Training errors account for a large share of exercise-related knee problems. The most frequent ones include:
- Increasing volume or intensity too fast. Tendons adapt more slowly than muscles. Adding too much running mileage, too many squat sets, or too much weight in a short period overwhelms tissues that haven’t caught up yet.
- Skipping rest days. Tendons need recovery time between loading sessions. Back-to-back heavy leg days or daily running without easy days built in sets the stage for tendinitis.
- Ignoring warm-ups. Cold, stiff tissues are more vulnerable to friction and strain. Even five to ten minutes of light movement and dynamic stretching before a session makes a measurable difference.
- Poor movement patterns under load. Letting the knees cave inward during squats and lunges, letting them shoot far past the toes, or landing from jumps with stiff legs all concentrate force on vulnerable structures.
- Worn-out footwear. Shoes that no longer provide support change how force travels up the leg and can contribute to both knee and IT band pain.
What Actually Helps
Exercise itself is one of the most effective treatments for knee pain, which might sound counterintuitive when working out is what triggered the problem. The distinction is between uncontrolled load (the activity that’s irritating the tissue) and targeted rehabilitation exercise (controlled loading that promotes healing and builds resilience).
For patellofemoral pain, the most consistently supported approach is strengthening the quadriceps and hip muscles. Wall sits, terminal knee extensions, step-ups, and hip abductor work form the backbone of most rehab programs. Eccentric exercises, where you slowly lower against resistance rather than lifting, are particularly useful for tendon problems because they stimulate repair while building the tendon’s tolerance to load.
In the short term, reducing the aggravating activity is important. That doesn’t necessarily mean stopping all exercise. It means dialing back the specific movement causing pain. A runner might temporarily switch to cycling or pool running. Someone doing heavy barbell squats might drop the weight and work on form, or substitute exercises that load the legs with less knee flexion. The goal is to find a training level that keeps you active without making the pain worse, then gradually build back up as the tissue heals and your supporting muscles get stronger.
Foam rolling the quadriceps and IT band can provide temporary relief by reducing tension in the tissues surrounding the knee. Stretching the hamstrings, calves, and hip flexors helps maintain the flexibility needed for clean movement mechanics. Neither replaces strengthening work, but both support it.