Patellofemoral pain syndrome (runner's knee)

Patellofemoral pain syndrome, often called runner's knee, is a common cause of pain at the front of the knee. It develops when the cartilage under the kneecap and surrounding soft tissues become irritated from overuse, misalignment or improper movement. Whether it affects your daily walks or your training schedule, understanding runner's knee is the first step toward relief.

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Detailed diagram of the human knee joint with labeled structures including the patella and ligaments.

Anatomy of the knee

The knee is a hinge joint made up of the thighbone, kneecap and shinbone. The kneecap sits in a groove at the front of the thighbone and glides smoothly as your leg bends and straightens.

With patellofemoral pain syndrome, the kneecap may shift slightly out of alignment or track unevenly within its groove. This can irritate the cartilage and nearby tissues, leading to pain, stiffness or a grinding sensation. Because the knee bears weight with every step, even a small misalignment or muscle imbalance can cause noticeable discomfort over time.

Overview

Symptoms

Runner's knee symptoms can develop gradually and often worsen with certain activities. Common signs include:

A dull, aching pain at the front of the knee
Pain during running, squatting, climbing stairs or prolonged sitting
Swelling or tenderness around the kneecap
Cracking or popping sounds with knee movement
Weakness or a feeling that the knee may give out

Symptoms often start mild and can intensify with continued activity, especially when climbing stairs or hills.

Causes

Several factors can contribute to patellofemoral pain syndrome, including:

Overuse: Repetitive bending, running, jumping or squatting that strains the joint
Muscle imbalance: Weak or tight muscles in the thigh, hips or calves that affect kneecap tracking
Improper alignment: An uneven gait or foot structure, such as flat feet or high arches, that alters knee movement
Trauma: Falls or direct impacts to the kneecap
Sudden activity changes: Increasing exercise intensity or duration too quickly

Identifying the underlying cause helps our specialists build a treatment plan that addresses the source of your pain and helps prevent future flare-ups.

Risk factors

Certain factors may increase your chances of developing runner's knee, though having one or more risk factors does not mean you'll develop the condition:

Participation in running, jumping or other high-impact sports
Sudden increases in training intensity or distance
Tight or weak thigh, hip or calf muscles
Flat feet or high arches
Previous knee injury

Knowing your risk factors can help you and your care team take steps to protect your knees going forward.

Diagnosis

Diagnosing patellofemoral pain syndrome starts with a conversation about your symptoms, activity level and medical history, followed by a physical exam that evaluates leg alignment, muscle strength, flexibility and kneecap movement. Your specialist may also recommend imaging, such as x-rays to check bone alignment and rule out arthritis or fractures, or an MRI to evaluate cartilage, ligaments and surrounding soft tissue. Findings are explained in clear, simple terms so you understand your condition and your options for care.

A diagram showing a healthy knee joint on the left and a damaged knee joint on the right, highlighting wear.

Common causes of knee pain

This video explains common conditions that can lead to knee pain and helps you understand what may be causing your symptoms.

Videos in our patient education library are available to help you gain a general understanding of the condition or procedure. Read disclaimer.

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