Patellofemoral pain

Patellofemoral pain (PFP) is the preferred term to describe pain around the patella (kneecap). It can also be known as:

  • patellofemoral pain syndrome
  • chondromalacia patellae
  • anterior knee pain

 

Patellofemoral refers to the articulation between the patella and the femur.

 

Figure 1: The patellofemoral joint

 i) Anterior view, the patella and tendon highlighted.

i) Anterior view, the patella and tendon highlighted.

 ii) Lateral view: extended position.

ii) Lateral view: extended position.

 iii) Lateral view with knee flexion.

iii) Lateral view with knee flexion.

 

The patella is what is known as a sesamoid bone - a "floating" bone - which is suspended in the quadriceps tendon. By acting as a lever arm for the quadriceps muscles it increases their strength significantly as well as dissipating force and reducing friction and compressive stress. 

The knee bears the brunt of some sizeable forces when we move and is affected by dysfunction or altered biomechanics of structures above and below it. As such it can develop a number of overuse syndromes and become stubbornly painful.

 

Symptoms:

People will normally describe a non-specific or vague pain and one which had no obvious mechanism of injury (however PFP can develop after an acute traumatic injury). Pain is often reported as moving around the patella and being quite diffuse. Activities that load the patellofemoral joint such as squatting, running, cycling or going up and down stairs are some of the more common troublemakers. Conversely, prolonged periods of sitting can also trigger an onset of symptoms, a condition known as "movie-goer's knee".

Any number of other symptoms can also sometimes be present including:

  • Occasional clicking or clunking
  • Crepitus - a grating or grinding sensation when a joint moves
  • Pain on contraction of the quadriceps 
  • Some restriction in knee range of movement
  • Limited swelling around the patella

 

 

What causes PFP?:

Because of the number of forces at play in and around the knee and the complexity of the gait cycle, there can be multiple factors that contribute to the onset of PFP. 

Extrinsic factors include: 

  • Ground reaction force when running (the body's contact with the ground)
  • Body mass
  • Footwear
  • Running surfaces
  • The speed of the gait cycle

Intrinsic factors include:

  • Local - position of the patella; dysfunction of the quadriceps muscles
  • Remote - poor lumbopelvic stability; foot pronation; increased rotation of femoral or tibial rotation during movement.
 

Figure 2: Remote intrinsic factors in PFP

  1. Poor lumbopelvic control elicits a pull down the outside of the thigh and onto the patella.
  2. Internal femoral rotation 
  3. Poor hip muscle control leads to abnormal movement of the knee.
  4. Foot pronation and inward tibial rotation.

 

How is it treated?

First and foremost an accurate assessment is paramount in establishing the intrinsic factors that are at play and subsequently which causal issues need to be addressed and corrected.

In terms of treatment the initial priority should be relief of pain. Occasionally pain-relieving medication may be required but more often the frequent application of ice will be beneficial. Specific taping techniques can also be very helpful and actually serve as a strong confirmation of the condition if that is the case.

Exercise is a huge part of PFP management. Strength training to the hip and quadriceps muscles is very important, but so too is endurance work for the stabiliser muscles around the trunk. In due course coordination exercises and activities specific to function will also need to be mastered.

 

Figure 3: Example of dynamic stability training - the "step and lunge"

 i) Preparing for split squat

i) Preparing for split squat

 ii) The step up phase

ii) The step up phase

 

Lengthening before strengthening...

Invariably upon assessment muscles in and around the hip and thigh will present as short or tight. These can have a significant bearing upon the mechanics of the lower limbs and, where found, shortness in these structures will need to be addressed.

 

Figure 4:

Quadriceps stretching. Accurate technique helps ensure efficient stretching of the rectus femoris muscle.