Knee Pain

Patellofemoral syndrome

Patellofemoral syndrome

What is patellofemoral syndrome?

Patellofemoral syndrome (PFS), also known as patellofemoral pain syndrome (PFPS) is a broad term used to describe pain in the front of the knee and/or around the patella that is aggravated by loading the flexed knee. It is sometimes called “runner’s knee” or “jumper’s knee” because it is common in people who are physically active, particularly women and young people.

Anatomy

Patellofemoral syndrome

 

(left) the patella normally rests in a small groove at the end of the femur called the trochlear groove.

(right) as you flex and extend the knee, the patella slides up and down into the groove.

 

 

 

Causes

Patellofemoral syndrome is multifactorial, where there are four main components:

  • Misalignment of the lower extremity and/or patella: the function of the patellofemoral joint is based on a complex interaction between static and dynamic structures involving the entire lower extremity such as the patellar tracks on the trochlea.
    • Static components include leg length discrepancies, abnormal foot morphology, hamstring and hip muscle tightness, angular or rotational deformities and trochlear morphologies.
    • Dynamic components include muscle weakness, ground reaction forces and insufficient or excessive pronation of the foot.

Multiple studies have concluded that weakness of the hip stabilizers may play a role.

  • Muscle imbalance of the lower extremity: a weak or unbalanced quadriceps musculature can cause malalignment of the patella within the trochlear groove.

Patellofemoral.syndrome

(left) in this MRI, the patella is normally aligned within the trochlear groove (arrows).

(right) here, the patella has moved out of the groove and is pulled to the outside of the leg (circle).

  • Hyperactivity/overloading: many patients with PFS do not show any signs of malalignment. Patellofemoral joint overload, on the other hand, has as risk factors:
    • Increased physical activity.
    • Level of physical condition.
    • Regime of the previous fiscal year.
    • BMI >25.

 

  • Trauma: direct or indirect injuries to the patellar area can damage the structures leading to the SLP.

 

Of the four contributing factors, overuse appears to be the most important.

Popliteal angle measurements have also been shown to be closely associated with the development of patellofemoral syndrome. Popliteal angle measurements are used to measure the flexibility of the hamstring musculature. A shortened posterior chain, primarily of the hamstring musculature, adds compressive forces across the patellofemoral joint, which increases the likelihood of developing PFS.

 

Treatment and prevention

The treatment of patellofemoral syndrome is divided into 2 main sections, the acute phase and the recovery phase.

  • The acute phase involves modification of the activity, such as changes in footwear or floor surface, or the use of inappropriate sports training techniques or equipment.

 

  • The recovery phasewhich attempts to correct the problem that most likely led to the development of the condition. The patient should undergo a muscular and joint assessment after following a conservative treatment of rest and possible cessation of physical activity or practice.