Patellofemoral Pain Syndrome

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Clinically Relevant Anatomy

Patellofemoral Pain Syndrome (PFPS) is a generic term used to describe pain at the front of the knee which comes on gradually with symptoms increasing over a period of time. It is sometimes also called anterior knee pain.

In general, patellofemoral pain syndrome occurs when the patella does not move or ‘track’ in a correct fashion when the knee is being bent and straightened. This movement can lead to damage of the surrounding tissues, such as the cartilage on the underside of the patella itself, which can lead to pain in the region. This injury is quite common in people who do a lot of sport, in particular adolescent girls.

When bending and straightening the knee, several structures surrounding the joint act together to cause the patella to run in a straight line within the intercondylar groove, formed by the Femur and Tibia. If any of the structures are particularly tight or weak, this causes an imbalance which can result in the patella mal-tracking. The most common example of this is when the lateral (outer) structures of the knee including the vastus lateralis, iliotibial band and lateral retinaculum are tight and the vastus medialis oblique (VMO) muscle on the inside of the knee is weak. This results in the patella moving too far laterally (to the outside) as the tight lateral structures pull it across and the medial (inner) muscles are not strong enough to control this force.

Patellofemoral knee pain can also occur following a knee injury, if the muscles of the quadriceps (especially VMO) become inhibited or considerably weakened.



  • Overloading – Bending the knee increases the pressure between the patella and the femur. Thus sports such as running, where repeated weight-bearing occurs, may result in PFPS.
  • Pronating Feet – Pronating or ‘flat’ feet lead to an increased biomechanical stress on the knee joint. This may affect the alignment of the patella particularly during movement.
  • Q-angle – Some people have a larger than normal femoral angle (known as the Q-angle) resulting in a ‘knock-kneed’ appearance (genu valgum). When the person straightens their leg when weight bearing, the patella will be forced to the outside of the knee. With repeated bending and loading, this motion may lead to damage of the underlying structures and cause pain.
  • A larger Q angle is common in women due to their wider pelvis. This is why more women suffer with this condition than men. Strengthening the abductors (Gluteus Medius, Minimus and Tensor Fasciae Latae) and lateral rotators (Gluteus Medius and Maximus) of the hip can be beneficial when a wide Q angle is thought to be a contributing factor.
  • PFPS is often confused with another condition known as Chondromalacia Patellae (CMP). This is damage to the cartilage which lines the underside of the knee cap. CMP can be a result of PFPS, although it can also occur independently, usually due to damage from an impact.

Who is most at risk from patellofemoral syndrome?

  • You are more prone to this if you have a small kneecap or one that sticks out
  • If your feet roll in or pronate.
  • If you suffer with tight muscles.
  • If you have weak quadriceps muscles.
  • Athletes who do a lot of long distance running or hill running.
  • Those who have had a previous knee dislocation

Characteristics and Clinical presentation

  • Aching pain in the knee joint, particularly at the front, around and under the patella.
  • Tenderness along the inside border of the kneecap.
  • Swelling sometimes occurs after activity.
  • Pain is often worst when walking up or down hills or stairs.
  • A clicking or cracking sound may be present on bending the knee.
  • Sitting for long periods may be uncomfortable. This is known as the theatre sign or movie-goers knee.
  • Wasting (atrophy) of the quadriceps muscles in prolonged cases.
  • A Q-angle greater than 18 to 20 degrees.
  • Tight muscles including calf muscles, hamstrings, quadriceps (especially vastus lateralis on the outside) and iliotibial band.

Differential Diagnosis

  • Patellofemoral OA
  • Peripheral neurogenic referral of the femoral nerve
  • Nerve root irritation and referral from the lumbar spine
  • Fat pad irritation.
  • Patella Tendinopathy
  • ITB syndrome.
  • Pre patellar busitis.

Assessment                           Knee Assessment           Back Assessment


Advice to patient:

  • Apply Relative rest, compression and elevation.
  • See a sports injury professional who can advise on treatment and rehabilitation.

Healthcare professional or Physiotherapy management

Check out this fantastic inservice training found online!

Presentation: Claire Robertson Clinical reasoning in PFPS

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