Runner's knee or patellofemoral syndrome (PFS)


Pain in the front of the knee and the kneecap


The patellofemoral joint is an unstable joint that is prone to subluxation or even dislocation, resulting in frequent knee pains, mostly located around the kneecap. The runner's knee is the main cause of knee pain consultations in both athletic and sedentary teenage girls with inadequate kneecap centring.

This condition, affecting a large number of athletes, can become chronic and evolve into arthritis.

In rare cases, this syndrome may appear after one or several occurrences of real patellar (kneecap) dislocations


The patellofemoral joint is a joint located at the front of the knee between the kneecap and the femur, that has the shape of a groove (trochlea). This joint connects the rear side of the kneecap, to the inferior, front side of the femur. It allows leg strength during extension, and plays a transmission role.

The causes of the patellofemoral syndrome

Severe causes

  • Fall on the knee with indirect trauma to the rear of the kneecap.
  • Kneecap dislocation caused by a forced knee movement.
  • Less frequently, knee sprain with associated torsion and dislocation of the kneecap.

Chronic or biomechanic causes

Kneecap instability with a tendency to subluxation related to:

  • Bad posture or wrong kneecap alignment,
  • Lack of muscle flexibility due to insufficient stretching,
  • Poor plantar statics,
  • Wrong alignment of the lower limbs such as valgum, varum or recurvatum,
  • High-riding kneecap (patella alta),
  • Lack of muscle toning and wrong toning ratio between the front and the rear of the leg (quadriceps/hamstrings).

What are the symptoms of a runner's knee

The main warning sign is: knee pain.

  • Pain at the front of the knee or around the kneecap when walking down the stairs, when hiking with altitude changes, or after prolonged sitting position.
  • Pain during and after sports such as breaststroke swimming, cycling with a poorly suited frame or muscle building (squats).

This pain is often delayed from the initial cause, meaning that the pain may occur after the workout:

  • Prolonged sitting position syndrome at the cinema or in the car,
  • Post-endurance syndrome 
  • Post-fall or -trauma syndrome.

Sports practices involved

  • doing squats,
  • running on macadam and with height differences such as bridges or tunnels,
  • doing steps exercise on a too high step,
  • walking or running downhill,
  • using a bike with a non-adjusted frame,
  • breaststroke swimming,
  • dances or acrobatics on hands and knees (or crouching),
  • etc…….

Non-sports daily practices involved

  • laying floor tiles or any work that requires resting on the patella (on the knee),
  • going down too many stairs carrying heavy loads, such as when moving out,
  • gardening in a crouching position,
  • spending too much time sitting in front of screens,
  • long car trips.

How can the doctor confirm a patellofemoral syndrome?

  • With a comparative physical examination of both knees, but most particularly with X-ray imaging (patellofemoral sunrise view and radiological assessment in axial positions)
  • IRM is of limited value, except to identify a mechanical or anatomical problem with worn cartilage.
  • Ultrasound scan
  • CT scan

The therapeutic management is mainly medical and "technical"

The objective: to eliminate the painful phenomenon and to recenter the patella, in order to allow return to previous activities

  • Avoid useless drugs that will not solve the anatomical problem and will at best hide the pain
  • Immobilization is useless, except for specific knee braces with patellar support that may be used to regain confidence,
  • Correct wrong practices, and most of all contributing habits such as physical inactivity,
  • Avoid overloads, sitting or crouching positions,
  • Rehabilitation and most of all muscular strengthening in extension, electrostimulation, stretching, and proprioception can provide durable relief of the painful syndrome,
  • Rest and ice when in pain, following use precautions and rare contraindications,
  • Wear orthopaedic insoles after performing a dynamic anatomical assessment,
  • Purchase new shoes suitable for your morphology,
  • Then resumption of walk++++with or without a pole, light running on flat and soft surfaces, and swimming with a preference for crawl; Resuming sports must always be done without pain and on flat surfaces, and be as little traumatic as possible - roads and macadam should be avoided
  • Self-rehabilitation in extension, doing alternate contractions,
  • Bikes should be adjusted, with a little higher saddle, and if you are an experienced cyclist, modify the cleat/pedal torque.


The patellofemoral syndrome is more common in women than in men, due to anatomical susceptibility, but it is observed both in people who do not have enough sport activities and in people doing a sport that contributes to kneecap strains and subluxations

The management includes adapted sport and rehabilitation, and the cases requiring surgery are rare


Docteur Patrick Bacquaert

Médecin chef de l'IRBMS

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The knee is a complex joint that supports the weight of the body. The bones, ligaments,tendons, and cartilage that make up the knee produce a flexible movement while maintaining the cohesion of the joint. It is important to take good care of your knees, which are heavily used during your athletic activities.