Knee Pain: Patellofemoral Pain (PFPS)

Patellofemoral pain (PFPS) is an umbrella term used to describe pain around or behind the knee

Julie Cai

November 15, 2022

Patellofemoral pain (PFPS) is an umbrella term used to describe pain around or behind the knee cap. It is also known as ‘patellofemoral joint syndrome’, ‘anterior knee pain,’ and ‘chondromalacia patellae’.  There are different pain-causing structures and biomechanical factors contributing to this presentation, which a Physio or Chiro would be able to assess and treat. This also means that each presentation of PFPS can vary widely.

Features of PFPS

PFPS typically starts during any weight-bearing activities involving knee flexion, running (especially downhill), steps, stairs and hills. The pain can feel non-specific, vague, or around and beneath the kneecap. It also can feel tender around the knee cap, or not at all, since the actual joint where the kneecap meets the thigh bone (femur) is inaccessible. There could also be occasional clicking, clunks or creaking in the knee. Squatting and stairs may also aggravate the pain.

Pain-Sensitive Structures

There are a few pain-sensitive structures within the patellofemoral joint (where the kneecap meets the femur) that could result in the sensation of pain. These include certain soft tissues such as the lateral retinaculum, the infrapatellar fat pad, or chemical or mechanical irritation within the joint due to a lesion in the cartilage within the joint.

Causative Factors of PFPS

PFPS is likely to be initiated by increased or unaccustomed loads onto the patellofemoral joint, which can irritate the structures within the joint. During weight-bearing activities, any increase in the amount of knee flexion (bending the knee) increases the load onto the joint. This commonly occurs through a higher training volume or increased speed of running, which could overload the PFJ structures sufficiently to initiate the pain.

When considering factors that may be contributing to the pain, it may be coming locally (around the kneecap), or remotely from other sources in the body.

Local factors contributing to pain:

Patella position

Any tension from surrounding soft tissue that pulls the patella laterally (outwards), posteriorly or rotate can cause irritation and pain in the knee joint. A common structure that pulls the patella outwards incorrectly is the iliotibial band (ITB) which may have increased tension from altered  pelvis and hip motion. This increases the tension on the lateral retinaculum which is a pain-sensitive structure, causing pain in the knee.

Soft tissue contributions

Tension in muscles such as the glutes, tensor fascia lata (TFL), iliotibial band (ITB), rectus femoris, hamstring and gastrocnemius can change the biomechanic load on the knee cap, resulting in increased load on the PFJ.

Motor control of the quadriceps

The inner part of the quadriceps called the vastus medialis obliquus (or the VMO for short), plays an important role in ensuring the kneecap is held synchronously during loaded flexion activities. Any delayed onset or weakness of this muscle allows outward tracking of the patella, which in turn creates non-optimal positioning of the kneecap itself. The side where there is knee pain also commonly has a smaller VMO. It is possible to retrain the strength and control of this muscle.

Remote factors contributing to pain:

It is important to consider what is happening as a whole in the lower body when looking at the knee. Biomechanical efficiency of the knee depends on the stability, strength and mobility of the hip and ankle. The main remote factors contributing to pain here are:

Increased femoral internal rotation

Increased inward rotation of the thigh bone (aka femur) inwards is associated with patellofemoral pain (1), and may contribute to its development (2). This can look like the knee caps facing inwards (medially), or the knee can turn inwards when doing a step-down, or single-leg squat test.

Increased apparent knee valgus

Increased femoral internal rotation, or if there is a drop in the pelvis during a step-down or single-leg squat results in an increase in knee valgus posture (seen in the picture above). These lower limb postures are potentially due to a weakness of the gluteus medius & VMO muscle, which require rehabilitation.

Increased tibial rotation

Increased rotation of the shin bone (aka the tibia) affects the load on the patellofemoral joint, and is strongly coupled with motion with the subtalar joint in the ankle.

Pronated foot type

Over-pronated feet, aka flat feet, is associated with patellofemoral pain and may contribute to its development (1) .

Inadequate flexibility

Inadequate flexibility may also be observed in all the muscles that affect knee movement. Aberrations in pelvis and hip motion may be influenced by muscles such as the glutes, tensor fascia lata (TFL), iliotibial band (ITB), rectus femoris, hamstring and gastrocnemius.

Treatment of Patellofemoral Femoral Pain Syndrome

An integrated approach to the management of an individual includes reducing the pain, modifying training loads and addressing both local and remote factors contributing to the pain. Since the presentation of PFPS is widely varied, it is important for your Physio or Chiro to identify the unique combination of factors contributing to the pain and treat accordingly. Depending on the causative factors, treatment can include trigger point therapy, myofascial release, patella mobilisation, modifying training loads, shoes or surfaces, taping and retraining altered muscle control patterns. Some individuals with a greater structural deviation in their foot may benefit from tailored orthotics to correct biomechanical dysfunctions.

If you have any further questions about how we can help with your knee pain, head over to our Contact Us page, or book in now to make an appointment.

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