Causes of Patellofemoral Pain Syndrome

The knee joint is actually a combination of two joints: the tibiofemoral joint (the hinge joint that most people think of when talking about the knee joint) and the patellofemoral joint (which isn’t so much a joint as it is a place where bones slide past each other). This article is going to focus only on the patellofemoral joint. This term describes the gliding articulation of the patella (kneecap) with the trochlear groove of the femur (thigh bone).

The patella glides up and down in the groove in the femur during knee flexion and extension. This groove helps facilitate keeping the patella lined up with the midline of the leg.

Incorrect Patellar Tracking

Patellar tracking is the term used to refer to the movement of the patella within the trochlear groove of the femur. Abnormal patellar tracking can lead to pain and dysfunction of the knee joint, or even the entire leg (through altering mechanics and causing hip, ankle, and/or foot pain). The two most common problems that are caused by improper patellar tracking are chondromalacia patella and patellofemoral pain syndrome (PFPS). This article discusses PFPS.

Identity Crisis

Patellofemoral Pain Syndrome is a catchall term/diagnosis that refers to pain in and around the patellofemoral joint that does not fall under another diagnosis. As a result of being an unclear diagnosis, the condition has a bit of an identity crisis, too. It is known as:

• Patellofemoral Pain Syndrome (PFPS)
• Patellofemoral Syndrome (PFS)
• Patellofemoral Stress Syndrome (PFSS)
• Patellofemoral Joint Dysfunction

PFS is one of the most common knee injuries sustained by performers. PFS can be either the primary (or only) diagnosis or it can be secondary to another diagnosis either in the knee or another lower extremity joint. PFS can also happen after certain surgical procedures on the knee.

Causes

Remember that song “the hip bone’s connected to the thigh bone…”? Well, strangely enough, it’s true! (for the most part) Injury or joint dysfunction of the hip or ankle/foot can actually cause pain only at the patellofemoral joint. This can make finding the true cause of PFS and, more importantly, the best treatment approach very challenging.

PFS symptoms can start after a direct blow to the front of the knee (like falling on it or being kicked or hit) or they can be caused through improper patellar tracking. When following acute trauma to the knee, the pain, alteration of mechanics, and swelling from the trauma cause PFS. However, the PFS symptoms associated with this mechanism of injury often resolve when the initial injury stops swelling and causing pain.

The most common cause of PFS is some sort of combination of overuse, poor structural alignment, improper mechanics, and muscular imbalances. Poor structural alignment can be associated with a lateral deviation of the patella from its normal track in the femoral groove. This lateral deviation can be caused by:

• Tightness of the hamstrings and gastrocnemius (large calf muscle)
• Tightness of the IT Band and the connective tissues on the lateral side of the knee
• Weakness of the quadriceps muscle that is supposed to pull the patella medially
• Weakness of the adductors that this quadriceps muscle (the vastus medialis oblique) is attached to
• Pronation of the foot
• Increased Q angle, typically seen in post-adolescent women

Pronation of the foot
Excessive pronation internally rotates the lower leg, changing the orientation of the patellofemoral joint by changing where the patellar tendon attaches in relationship to the origin of the quadriceps muscles.

Additionally, pronation of the foot in turnout, frequently caused by forcing turnout from the ground up, places a great deal of stress on the medial knee and the medial aspect of the patella during activities like plie. Not only can doing plies in bad alignment lead to PFS, landing jumps in this bad alignment could lead to a patellar dislocation, MCL sprain, ACL sprain (remember, a tear is a type of sprain), and meniscus tears. Do not force turnout, and DO NOT LAND WITH YOUR KNEES GOING IN (keep them in line with your second toe)!

Q angle
The Q angle describes the relationship between the line of pull of the quads and the orientation of the patellar tendon. Increased Q angles are associated with wider hips and with knock-kneed postures. The amount of pressure applied through the patellofemoral joint increases with increased Q angles, contributing to pain, dysfunction, and inflammation caused by improper patellar tracking.