Patello-Femoral Pain Syndrome

Anatomy


Our knee is consisted of 3 compartments:

  1. Medial Compartment
  2. Lateral Compartment
  3. Patello-Femoral Compartment

The medial and lateral compartments are the main weight bearing compartments  usually referred to as the knee joint.   Inside these two compartments are ligaments (i.e. cruciates & collaterals) for stabilization and meniscus for shock absorption and cushioning. 

Unlike the medial and lateral compartments of the knee, the knee cap (i.e. patella-femoral compartment) is not a weight bearing joint.    The knee cap, being a floating bone, is situated to the front and forward of the main knee joint.

Unlike the main joint of knee, position of the knee cap is determined by soft-tissue surrounding it.    The knee cap is, in fact, part of the quadriceps muscle, whose function is to provide mechanical advantage by acting as a lever when the knee is straightened and bent.    Hence, the knee cap is not static but tracks up and down as your knee bends and straightens.

What is Patello-Femoral Pain Syndrome?

Also known as Chondromalacia Patellae,   Patello-Femoral Pain Syndrome (PFPS) refers to a mechanical problem in the tracking mechanism between the knee cap and the main knee joint.     If tracking of the knee cap is less than ideal,   then during bending and straightening of the knee,   the back of knee cap may scrap against the knee joint thereby resulting in pain, inflammation, crepitus, and weakness.

Causes

There is no single causation leading to inefficient tracking of the knee cap against the knee joint.   Because the knee cap is a floating bone, its’ position and tracking can be affected by a number of factors that can place excessive stress to this lever mechanism.   Common factors which can affect tracking of the knee include:

Factors

Significance

Genetics

Some individuals have more inherent laxity in their joints (i.e. mobility in the knee caps)  than others.

Gender

Young girls tend to have more laxity in their joints than boys.

Patella Position

Some knee caps are positioned higher/ lower, or more deviated to a side causing more effort and stress for tracking.

Shape

When in standing,   our legs act like a chain with force being transmitted upwards.   Whenever there is a deviation from the ideal alignment in the shape of our legs,  force associated with standing will be transmitted upwards from one joint to the next.    Many structural deviations such as flatfeet, bowlegged, or wide pelvis angle, though not pathological in themselves,  may add additional stress to the knee cap during tracking.

Obesity

Your knees have to work harder because of extra body weight.

Age & Disuse

As one ages, and perhaps with insufficient exercises,  the quadriceps muscles,  which the knee cap is part of,  may loose some of its’ strength.   With less strength,  the quadriceps will have more difficulty to control the knee cap in its’ tracks.

Activities

In addition to underlying factors discussed above, symptoms of PFPS are often brought on by excessive physical activities which “overload” the knee cap tracking mechanism.    These physical activities often include repetitive squatting, knee bending, or running.   

How Severe Can This Get?

  1. Children/Teenagers

For some kids with a lot of joint laxity and mobility in their knee caps,   the  risk exists for spontaneous knee cap dislocation during strenuous physical activities such as running,  jumping, and squatting.   This is a quite a painful experience as the knee cap, under excessive stress, would dislocate to one side and spontaneous relocate itself resulting in swelling, pain, and restricted range of motion.

  1. Adults & Seniors

For more chronic Patello-Femoral Pain Syndrome, the key is to prevent it

from worsening as repeated scrapping between the back of knee cap and the knee joint can lead to osteoarthritis in the patella-femoral compartment.  For most cases,   inefficiency of knee cap tracking can be controlled by quadriceps strengthening exercises and protection.

Treatment Options


Prognosis

There is no structural “fix” for Patello-Femoral Pain Syndrome because for most individuals, there are some form of underlying factors which caused mechanical disadvantage for tracking of the knee cap.  Exception is if you had recurrent dislocations which warrant surgical tightening.      

For most cases,   conservative treatment including combination of medications, physiotherapy, and protection is sufficient to control signs and symptoms arising from inefficiency of knee cap tracking. 

Long term goal is to provide sufficient stabilization to the knee cap through quadriceps strengthening and protection (knee brace with open patella or taping) for maintenance.