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Knee Pain: Patellofemoral Pain Syndrome Symptoms and Cause

What Pain and Symptoms Are Associated With Patellofemoral Pain Syndrome?

Patellofemoral Joint

The PF joint includes the femur (thigh bone) and patella (knee cap). Though it is not seen in the diagram, the end of the femur has a track known as the trochlear groove which allows the the knee cap to glide up and down when you bend and straighten your leg.

  • Pain is felt in the front of the knee, under and around the knee cap area.
  • Pain is usually an aching pain but can sometimes become sharp and in some cases a burning sensation is felt.
  • Knee will pop and grind during bending and straightening
  • Knee buckling – the knee and leg do not support your weight
  • Knee feels weak and feels like it is going to give out
  • Pain is worse when climbing or going down stairs as well as up and down inclines
  • Kneeling and squatting are very painful especially when you rise back to standing position
  • Pain increases while sitting for prolonged periods.

What is Patellofemoral Pain Syndrome?

Patellofemoral pain syndrome is one cause of pain in the front of the knee.  The pain is felt around and under the knee cap and will sometimes off to the sides of the knee.

Activities That Make Patellofemoral Pain Worse:

  • Going up and down stairs
  • Going up and down inclines (including inclines on treadmills)
  • Running, jogging, and power walking
  • Riding a bicycle or stationary bike
  • Sitting for extended periods of time
  • Some exercise that involves bending, straightening, rotating or twisting the knee

What Are The Causes Of Patellofemoral Pain Syndrome?

Muscles that can cause knee cap pain

The outside muscles of the leg including the IT band can over power the muscles of the inner thigh causing the knee cap to shift toward the outside of the leg causing pain.

PF pain syndrome is often diagnosed but little is known about the actual cause. There are several possible causes to this little understood pain syndrome.  The most commonly known contributors are:

  • Misalignment of the knee cap.  Misalignment often begins with a twisting injury of the knee or a direct blow to the knee. The misalignment can be a full dislocation or a more subtle movement of the knee cap toward the outside of the joint. If not corrected, misalignment can cause a wearing down of cartilage, wearing of the knee cap and thigh bone (femur), and damage to the synovial lining which provides cushioning and lubrication. Check out this diagram of patella (knee cap) malalignments.
  • Muscle imbalance in the upper leg muscles. One of the most commonly observed signs of PF pain are weak quadriceps muscles, primarily the vastus medialis, located on the inner thigh. When this muscle is weak, it allows the vastus laterialis and the IT band located on the outside of the thigh to pull the knee cap toward the outside of the joint out of its normal alignment.
  • Patellofemoral osteoarthritis – Osteoarthritis or degenerative joint disease is just that, a degeneration or breakdown of the joint. The causes of osteoarthritis are many and varied including: hereditary, obesity, stress to the muscle and skeletal system, previous injuries, and peripheral nerve impairment. A recent study at the University of Manchester showed that a particular knee brace helped reduce pf osteoarthritis pain significantly. Read about the study and the knee brace used in the study.
  • Wide set hips increase the angles of the femur to the knee, which puts stress on the kneecap.  This may explain why women are two times more likely than men to experience patellofemoral pain.
  • A pronated foot is a foot that rotates inward toward the other foot. A sign of pronated feet is that you wear down the inside sole of your shoes, your shoes ‘lean’ toward the inside and calluses on the inside bottom of the foot. Walking on the inside of your foot rotates the lower leg inward stressing the knee joint as well as the kneecap.
  • A supinated foot is a foot that rotates to the outside. If you have a supinated foot your shoes will lean toward the outside and the soles of the shoes will wear on the outside of the shoe. You may also have calluses on the outside of the foot. Walking on the outside of your foot rotates the lower leg toward the outside putting stress on the knee joint and kneecaps. Diagram of supinated and pronated foot.
  • Genu Valgum: Knock Knees – Knock knees can affect one or both legs. The knee(s) angle in toward the other leg twisting the knee joint which puts excessive pressure and force on the outside of the joint.
  • Pinching of the synovial lining between the knee cap and upper thigh bone (femur). There are times when knee pain is not caused by injury, knee cap displacement or any other apparent dysfunction. In some of these cases surgeons have found that the synovial lining the cushion between the bones in a joint, is pinched between the femur and knee cap.

In 2005 surgeon and researcher Scott F. Dye, MD elected to have knee surgery without anesthesia to find the source of his chronic knee pain. Using a probe to test various structures for pain, Dr. Dye touched various areas in the knee trying to replicate the pain. He was surprised to find that when he probed the cartilage there was no pain. Damaged, torn and worn down cartilage have often been blamed for painful knees. However when the doctor touched the synovial lining, he found that area replicated his pain. This brave experiment seems to confirm some surgeon’s suspicions about the “pinching” of synovial lining. You can read the article, “The Pathophysiology of Patellofemoral Pain“.

Clinical Diagnoses Which Maybe A Factor:

  • Patellar tendinitis
  • Quadriceps tendinitis
  • Patellar bursitis
  • Patellar subluxation
  • Pattelar dislocation
  • Patellofemoral arthosis
  • Knee ligament injury

Interesting facts about patellofemoral pain:

  • Because the pain is always in the front of the knee, PF pain syndrome is also called anterior knee pain.
  • PF pain syndrome is often called runners knee.
  • It is also known as theatre sign or movie goers knee because sitting for long periods of time causes pain and stiffness

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