Runner's Knee (Patellofemoral Pain)

What it is

Runner's knee is poorly defined pain at the front of the knee. Its onset can be slow or sudden, it gets worse with loading of the lower limb such as squatting, prolonged sitting, stairs, jumping or running, and it can recur and persist for years. Many other problems cause knee pain, so the first step is an examination by a clinician.

What causes it

A 2020 review of patellofemoral pain in runners states that current evidence does not identify alignment, muscle weakness, kneecap maltracking or a combination of them as causes of the pain. It points instead to the external load, such as changes in training and running biomechanics, and the internal load, such as sleep and psychological stress¹. So look first at what changed in your training, your sleep and your stress.

What treats it

A 2024 best practice guide combined a meta-analysis of 65 trials, interviews with people who have the pain and interviews with clinical experts. It recommends exercise therapy aimed at the knee, with or without exercise aimed at the hip, together with education as the primary treatment, and adds foot orthoses, manual therapy, movement or running retraining and taping to suit the person².

A Dutch multidisciplinary guideline also starts with exercise therapy. It adds other conservative treatments only if exercise therapy has not produced a clinically relevant change after six weeks, so give the exercise six weeks before judging it. It rates the certainty of the evidence for exercise therapy as low to very low, and the panel recommends it as the first treatment anyway³.

In a 2018 trial of 69 runners with the pain, three 8-week programs were compared: education on managing symptoms and modifying training; the same education plus exercises; and the same education plus gait retraining. All three groups improved by a similar amount at 4, 8 and 20 weeks. The gait retraining group raised its step rate and lowered its impact loading, and still improved no more than the others. Every group got the education, so the trial does not show how much of the improvement the education itself produced. The authors conclude that education on symptoms and on managing training load should be a primary part of treatment in runners⁴. You do not need to rebuild your stride to treat it, and you do need a plan for your load.

Running with it

The 2020 review recommends graded exposure to load, including movement, exercise and running, while allowing for capacity, which includes sleep and psychological stress¹. Day to day that looks like this:

• Cut back whichever of volume, hills or speed brings the pain on. A physical therapist's rule for returning runners: pain stays at 3 out of 10 or lower (4 at most) while you run and is stable or improving over the weeks, you stop the run if it climbs above that, and the knee is back to its usual level within 24 hours of finishing. A limp, or any change in how you move, is a stop. Your clinician may set a different limit. The guide on return to running covers the order of return.
• Replace the running you cut with aerobic work that adds no lower-body impact and does not provoke the knee, at an easy conversational effort, which is zone 2 in a five-zone model.
• Do the knee and hip strengthening your clinician prescribes, and keep it in your week once the pain settles (see the guide on strength training for runners). Single-leg work suits a runner whose sides differ in strength.
• Rebuild so that no run is much longer than your longest run of the last 30 days. In 5,205 runners followed for 18 months, injuries were more common when a session was more than 10% longer than that⁵. Bring hills back last.

When to see a professional

A clinical diagnosis comes first, with exercise therapy as the first treatment³. See a sports-medicine professional if the pain is not easing after a couple of weeks of reduced load, if it limits daily activities or if you are unsure what is going on. A kneecap that slips or gives way, or a knee that locks, is a different problem and needs prompt care.