One of the most common causes of knee pain that I have encountered in practice, especially amongst active individuals, is pain related to patellofemoral syndrome. Commonly called “runner’s knee,” it is often manifested by pain under or around the kneecap. In this article, you’ll learn all about patellofemoral syndrome, including what it is, why it occurs, and how it can be treated.
Defining terms and anatomy
Patella is the Latin medical term for the kneecap bone and femur is the Latin term for the thigh bone, which runs from the hip to the top of the knee. The femur is the longest bone in the body. The patella sits on the front of the bottom end of the femur. The term patellofemoral comes from the interactions of the kneecap and the thigh bone underneath it.
The patella is not just floating on top of the femur. It is attached by several structures. Imagine the patella as a clock (my one year old son’s favorite household item). At the 12 o’clock position on the top of the clock, the quadriceps tendon attaches to the patella. This tendon is the end of the quadriceps muscle at the front of your thigh.
On the bottom of the patella at the 6 o’clock position is the patellar tendon, a tendon that connects the patella to the tibia, or shin bone.
On either side of the patella are ligaments at the 3 and 6 o’clock positions. They are termed medial, or inner patellofemoral ligament, and lateral, or outer patellofemoral ligament. Hopefully, all this jargon makes more sense now.
What exactly is patellofemoral syndrome?
Patellofemoral syndrome is a catch-all phrase indicating injury, inflammation, or pain to any of the above-mentioned structures. Patellofemoral syndrome could mean a strain of one of the ligaments on the side of the patella or one of the tendons on top of the bottom. It could also mean pain behind the kneecap.
How is patellofemoral syndrome caused and why does it occur?
Patellofemoral syndrome is generally caused by the weakness of certain areas of the leg. If any the supporting structures of the knee mentioned above (quad tendon, patellar tendon, and medial and lateral ligaments) are weak, the patella is not properly supported. As a result, it may “bump” into the bone behind it because it is not being held up properly. This worsens with repetitive leg bending activities such as running, stairs, and even prolonged walking. The more the patella hits into the femur bone behind it, the more it causes pain and inflammation.
Another possible cause of patellofemoral syndrome is muscle imbalance. If one side of the thigh (inside or outside) has stronger muscles than the other, this pulls the patella to the stronger side. I imagine this being like a game of tug-o-war. I commonly see this issue in cyclists – riding a bicycle builds up the outer quadriceps muscle so much that by comparison, the inner muscle is weak. The outer muscles pull the patella to the outside. This causes the inner medial ligament to stretch and therefore, to become strained.
How can patellofemoral syndrome be treated?
Patellofemoral syndrome is a mechanical problem so treatments are aimed at correcting mechanics. In the meantime, if the pain and inflammation are severe, anti-inflammatory medications can be used, assuming no medical contraindications (heart, blood pressure, or gastrointestinal issues). Ibuprofen, naproxen, and meloxicam are examples of anti-inflammatories that can help with symptoms initially. These will not solve the problems that caused patellofemoral syndrome but could give relief in the interim.
Bracing is also a good treatment. Just like braces on teeth, wearing a knee brace can help to place the patella in proper alignment and prevent it from moving out of place. Called a patellofemoral stabilizer brace, this is best worn with activities that cause pain. These will be individually specific but could range from walking to competitive sports. The brace should not be worn at all times as this can lead to muscle weakness from becoming dependent on the brace. Eventually, when the muscles become strong enough to align the patella on their own, the brace should be discontinued. This leads to the next treatment category – physical therapy.
Physical therapy is the mainstay of treatment for patellofemoral syndrome. Physical therapy includes manual treatment from the therapist aimed at loosening tight muscles and helping to realign the patella. The physical therapist will also instruct on stretching and strengthening exercises aimed at helping the body realign the patella. This will be individually tailored to the specific patient.
In the example above, if a cyclist has weaker inner thigh muscles as compared to outer thigh muscles, physical therapy will be aimed at strengthening these inner muscles. If the entire quadriceps are weak, then exercises can be tailored to this as well. A strong home exercise program, arranged by the physical therapist, goes hand in hand with formal PT. PT appointments are generally only a couple times per week but it is important to work on these exercises almost daily.
Prognosis of Patellofemoral Syndrome
With bracing, a good physical therapy regimen, and a consistent home exercise program, most patients recover from patellofemoral syndrome in about 6-8 weeks. Some take shorter and some take longer. Even after feeling better, it is imperative that the home exercise program is continued to maintain the improvements in strength.
If symptoms are not improving with physical therapy, bracing, and anti-inflammatory medication alone, it may be time to get an MRI to see if there is any structural damage to the cartilage, ligaments, or tendons.
Occasionally, especially with longstanding patellofemoral syndrome, the cartilage behind the kneecap can wear away. In these cases, injections of a lubricating gel called hyaluronic acid could help symptoms by reducing the friction and inflammation from the cartilage rubbing together. Other more extreme options for cases not amenable to conservative measures include surgery to realign the patella and joint replacement surgery which replaces the areas of cartilage wear with artificial metal surfaces.
Have you experienced patellofemoral syndrome (runner’s knee)? What treatment options worked best for you? Share your story in the comments below?