Making Sense of Patellofemoral Pain

By Declan Chapman

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Note: This information is general in nature and does not constitute medical advice. If you think you have patellofemoral pain you should consult a registered health professional for personalised advice specific to your presentation.

 

Patellofemoral pain is a broad term which describes discomfort at the front of the knee and around the kneecap (patella). It is often referred to as “runner’s knee” or “jumper’s knee” given it’s prevalence in athletes. The pain and stiffness experienced with patellofemoral pain can make it difficult to climb stairs, kneel, squat, or carry out daily activities. There are several proposed mechanisms which may contribute to patellofemoral pain including misalignment of the patella, overuse of quadriceps, and excessive loading. Fortunately, many people experience relief from patellofemoral pain without requiring any surgical input.

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Brief Explanation of the Anatomy

To understand patellofemoral pain, you first need to understand the anatomy of the knee. The knee is made up of 3 bones (femur, tibia, patella) which are connected by strong ligaments, tendons, and connective tissue. The diagram below illustrates this:

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The quadriceps tendon connects the front thigh muscles (quads) to the patella. The quadriceps tendon also attaches to the tibia to create stability through the patella. This fibrous band is called the patella tendon.

 

The patellofemoral joint has several structures which promote efficient movement. The patella sits in a groove at the front of the femur known as the trochlea. Whenever the knee is bent or straightened, the patella can move back and forth within the trochlear groove. The bottom of the femur, trochlear groove, and underside of the patella are covered by articular cartilage. This smooth surface acts as a natural lubricant to allow the bones to glide smoothly against each other.

 

The femur and tibia are separated by the meniscus. There are two C-shaped menisci in each knee (one on the inside and one on the outside). The meniscus acts as a force distributor for the knee joint - protecting and stabilising it. The articular surfaces (connecting surfaces) of the knee joint are covered in a thin layer of tissue known as the synovium. The synovium produces a small amount of fluid which further lubricates the cartilage to allow smooth gliding. Finally, there are several small pads of fat known which sits above, below the patella, and behind the knee to assist in force distribution and shock absorption.

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What Causes Patellofemoral Pain?

Patellofemoral pain occurs when nerve receptors in the patella tendon, infrapatellar fat pad, synovium, or bone, receive abnormal messages. These messages are then interpreted in our brains as being damaging and painful, leading us to experience pain at the front of the knee. Whilst there is some conjecture on exactly what leads to patellofemoral pain, there are generally 2 primary causes:

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1. Overuse

   • Repetitive physical activity which places stress on the knee (jogging, squatting, climbing)

   • Significant increase in physical activity intensity or volume

   • Other factors which may contribute include poor running technique or movement quality, changes in footwear, changes in running or playing surface, and changes in dietary habits.

2.  Patella Misalignment

   • ​​​Abnormal tracking of the patella within the trochlea may also lead to patellofemoral pain. If the patella is forced to one side of the groove when the knee is bending, then pressure behind the patella will increase resulting in irritation to the soft tissue.

   • Muscle imbalances in the quadriceps may also affect the tracking of the patella in the trochlea groove. If the inner quadriceps (vastus medialis) is significantly stronger than the outer quadriceps (vastus lateralis), you may see a shift of the patella toward the stronger side.

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It is important to note, that when we experience patellofemoral pain, there is not always a structural problem. However, in some cases, the pain may be the consequence of a condition known as chondromalacia patellae. This occurs when the articular cartilage on the underside of the patella softens as result of repetitive loading, creating increased friction in the joint. This friction leads to inflammation of the synovium. The nerve receptors in the synovium and bone detect this inflammation giving us pain. Another possible explanation is poor alignment between the hip, knee, and ankle resulting in poor biomechanics. Genetic abnormalities may also result in patellofemoral pain. One example is patella alta. This is a condition where the patella sits abnormally high, above the trochlea groove.

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Common Signs and Symptoms

• Dull ache at the front of the knee.

• Minimal pain at rest but is aggravated gradually with activity.

• Pain with bending, climbing stairs, running, jumping, squatting.

• Pain with prolonged sitting or kneeling.

• Pain worsens when activity intensity or volume is increased.

• Popping or cracking when climbing stairs or after standing up.

 

What to do about it

1. Activity Modification: minimise the time spent doing activities which aggravate the knee.

2. Load Management: Avoid placing unnecessary load on the knee while it is acutely painful.

3. Compress: To prevent further swelling wrap the knee in a compressive bandage with a hole for the patella. Ensure the wrap is not too tight to cut off circulation or prevent movement.

4. Physiotherapy: Manual therapy can help facilitate healing processes, reduce pain, and create comfort through the knee. Specific exercises are required to improve pain free range of motion, strength, and muscular endurance.

 

Although this condition is usually easily treatable, it may take between 6-12 months to fully resolve. If you think you may have patellofemoral pain, please get in touch with us today.