Runner's Knee: What It Is, Why It Develops and How to Get Rid of It

What is runner's knee?

Runner's knee is the colloquial term for patellofemoral pain syndrome (PFPS). It is pain around or behind the kneecap, caused by abnormal pressure or friction of the kneecap (patella) on the thigh bone (femur).

The kneecap slides into a groove on the thigh bone when the knee is bent and extended. If that movement is not smooth because the kneecap pulls out or in too much, friction occurs on the cartilage at the back of the kneecap.

PFPS is not structural damage in the sense of a crack or break. It is a functional problem: the kneecap does not move optimally, and that repeated friction over thousands of steps results in pain.

Symptoms

• Pain around or behind the kneecap, often vaguely localized
• Pain that increases when climbing stairs, walking downhill or sitting for a long time with the knee bent (the "theater syndrome": pain when sitting for a long time with the knee bent)
• Pain that builds up the longer you walk, especially when descending
• A cracking or grinding sensation when bending the knee (crepitation), sometimes audible
• Stiffness after sitting for a long time

The real cause: it's not a knee problem

This is the misunderstanding why runner's knee is so often mistreated. Most runners (and unfortunately some healthcare providers) treat runner's knee as a knee problem. But the kneecap moves abnormally due to forces coming from higher up.

The kneecap is controlled by the quadriceps, in particular the vastus medialis (the muscle head on the inside of the thigh). But the position of the knee while walking is determined by the hip. A weak gluteus medius causes the femur to rotate inward, causing the kneecap to pull outward relative to its groove.

Research consistently confirms this: runners with runner's knee have significantly weaker hip abductors and hip external rotators than symptom-free runners. Treatment aimed at the hip gives better and more lasting results than treatment aimed at the knee alone.

Risk factors

Weak hip abductors and gluteus medius: the most determining risk factor. The hip stabilizes the leg during each landing phase. Those who don't have that will see the femur adduct (fall inwards) when landing.

Building up volume or intensity too quickly: the muscles that stabilize the kneecap become tired and perform less when overloaded.

Overstriding: a foot landing too far in front of the body increases the forces on the knee. Read more about step length and foot landing.

Downhill trails and hill training: Running downhill significantly increases the forces on the kneecap.

Female runners: on average, have a slightly wider pelvis, which increases the Q angle (the angle of the quadriceps relative to the kneecap). This statistically increases the chance of PFPS.

Treatment

Phase 1: tax reduction

Decrease walking volume and avoid activities that aggravate pain: walking downhill, climbing stairs, sitting for long periods of time. This reduces the irritation of the cartilage. Ice on the kneecap (15 minutes, several times a day) provides pain relief in the acute phase.

Phase 2: hip strength training

This is the core of the treatment. The exercises that are the most evidence-based for PFPS:

Clamshells: Lying on the side, knees bent, lifting the top knee like a clam opening. Isolates the gluteus medius.

Side-lying hip abduction: lying on the side, lift the top leg with the knee extended. Trains the entire hip abductor.

Single-leg squat: lower on one leg to a half-bent knee angle. Trains hip, quadriceps and stabilizers at the same time. Check that the knee does not collapse during the movement.

Hip thrust: lying on your back with feet on the floor, lift pelvis. Trains gluteus maximus.

Step-up: One foot on a step, lifting the body by straightening the leg. Trains gluteus medius and quadriceps in functional position.

Build the strength twice a week. Results are visible after four à eight weeks of consistent work.

Phase 3: running technique adjustment

In addition to hip strength training, an adjustment in running technique can reduce the pressure on the kneecap:

Higher cadence: an increase of 5 à 10% reduces knee strain when landing. Read more on the cadence page.

Slight forward torso: Leaning slightly more forward shifts the ground reaction force from the knee to the hip.

Point of view on landing: Focus on actively pulling the foot back upon landing rather than pushing it forward.

Phase 4: gradual return

Once the pain during daily activities has disappeared and the hip strength exercises are going well without knee pain, start with easy, level walks. Use ourcomeback guide as a guide. Avoid downhill courses until you are completely free of complaints.

How long does recovery take?

With an early and targeted approach: four à eight weeks. In a chronic case where the cause has not been addressed for a long time: three to six months. PFPS that does not respond to conservative treatment (hip strength training, technique adjustment, load reduction) deserves evaluation by a sports physician or orthopedist.

Frequently asked questions

In summary

Runner's knee is a hip problem that manifests itself in the knee. Treat the hip, and the knee improves. Targeted hip strength training twice a week, combined with a slight cadence increase and patiently built up training load, is the most effective approach for most runners.

→ Do you want to prevent runner's knee from coming back? The prevention page explains how to structurally strengthen your hip.
→ Ready for the comeback? Read the comeback guide.