Why Does My Knee Hurt When I Run?

Why the knee takes the hit.

The knee sits between the hip and the foot. When either of those areas is weak, stiff, or poorly controlled, the knee often ends up absorbing the difference. Every running stride loads the knee, and over hundreds or thousands of strides a small mechanical issue can add up to real pain.

Training habits matter just as much. A sudden jump in mileage, more hills or speed work than usual, or a new pair of shoes introduced all at once can outpace what your tissues are ready for. Our pages on running injuries and hip and knee pain go deeper into both sides of the problem.

Common causes of knee pain in runners.

Runner's knee (patellofemoral pain)

Pain around or behind the kneecap, often worse on stairs, squatting, running downhill, or after sitting for a while. It is frequently linked to weak hip muscles or a foot that collapses inward, which changes how the kneecap tracks.

IT band syndrome

Pain on the outside of the knee that tends to build at a predictable point in a run. Weak hip muscles can leave the IT band overworked.

Patellar tendinopathy

Pain just below the kneecap, where the tendon attaches, often after jumping, hills, or faster running. Like other tendon problems, it usually reflects more load than the tendon can currently handle.

Something structural

Swelling, locking, catching, or a knee that gives way can point to a meniscus or ligament problem rather than an overuse issue. Those symptoms need a proper evaluation before you keep running on them.

What you can adjust right now.

For overuse-type knee pain without swelling or instability, a few changes often help:

• Reduce, do not necessarily stop. Cutting back mileage, pace, or hills for a period is often enough to let symptoms settle while you stay active.
• Use pain as a guide. Mild discomfort that settles quickly and does not change your stride is different from pain that builds during the run, makes you limp, or is worse the next morning.
• Build strength. The hips, thighs, and calves all help control the knee. Strength work two or three days a week is a common part of running injury rehab.
• Cross-train while things settle. Cycling, swimming, or other lower-impact options can maintain fitness while you reduce running, as long as they do not provoke your knee.
• Make changes gradually. Increase distance, speed, and new shoes or surfaces a little at a time rather than all at once.
• Do not run through pain that changes how you move. Compensating can create a second problem.

How physical therapy gets you back to running.

An evaluation looks at the whole picture: your training history, hip and ankle strength and mobility, how your knee tracks during single-leg tasks, and how you move when you run. That tells us which part of the chain is overloading your knee.

Treatment usually combines targeted strengthening for the hips, thighs, and calves, hands-on care to reduce pain and restore motion when needed, and a structured plan for how much to run while you recover. As you improve, sports rehabilitation bridges the gap from basic strength to full running, with a gradual return-to-run progression so your knee is tested in steps rather than all at once.

A return-to-run plan often starts with walk-run intervals or shorter, flatter routes, and builds distance before speed or hills. Your therapist will set clear checkpoints, such as how your knee handles single-leg strength tests and how it feels the morning after a run, so you know when it is reasonable to progress and when to hold steady.

The goal is not just a quieter knee for a week. It is a body that can handle the training you want to do. You can request an appointment whenever you are ready.

When to see a doctor first.

Contact your doctor or seek urgent care if you have:

• A pop at the time of injury followed by rapid swelling
• A knee that locks, catches, or gives way
• Inability to put weight on the leg
• A hot, red, swollen knee, especially with fever
• Calf pain with swelling, warmth, or redness
• Pain that is sharp and focused on one spot of bone, or that is present at rest and at night

These symptoms are less common than typical overuse pain, but they deserve medical attention before you return to running.