This knee problem is quite common in runners. If a runner has mild to severe knee pain in a site other than the outside of the knee and they don't have any previous history of knee injury, it's a good guess that there's some degree of PFS contributing to the pain. The pain is usually described as being located around or under the knee cap. PFS is also one of the most mis-diagnosed running related injuries, so read on.
Patello-Femoral Syndrome is a condition caused by the patella (knee cap) not tracking properly over the femur (thigh bone). The patella normally rides in a groove on the femur. The patella is really a fulcrum - it gives leverage to the big muscles on the front of the thigh. These thigh muscles are called the quadriceps - or quads for short. The quads are so named because they consist of four muscles. With PFS, you get an imbalance in these muscles - usually the lateral or outside muscle over-powers the inner medial muscle - and this pulls the patella out of it's normal groove. When the patella doesn't track properly in it's groove, it causes pain under the patella.
As I stated above, PFS is often mis-diagnosed. It's often mis-diagnosed as Chondromalacia Patellae. This is a chronic, degenerative condition that affects the underside of the patella. The underside starts to soften (malacia means soft) and when it rubs on the femur it causes pain. Chondromalacia Patellae is thought to be a sequelae of long term PFS. In other words, PFS may progress to Chondromalacia over time. Mis-diagnosis occurs when a complete examination is not performed. Because these two conditions present with almost identical signs and symptoms an x-ray is often necessary to differentiate between the two. A special view called a "Skyline" view of the knee will show the underside of the patella which allows us to look for softening of the cartilage. There's a classic presentation on x-ray called "Crab Meat Sign" (the cartilage starts looking like crab meat!) that is indicative of Chondromalacia Patellae. Chondromalacia Patellae is only truly diagnosed with a positive Crab Meat Sign on x-ray. If you've been told that you have Chondromalacia Patellae but you haven't had an x-ray, or the x-ray doesn't show the Chondromalacia Patellae, get a second opinion.
Now, with that said I should also state that conservative treatment for both PFS and Chondromalacia Patellae is essentially the same, however Chondromalacia Patellae may sometimes require surgery so you want to make sure you have the diagnosis correct before you let anyone cut into you're knee!!
Signs and Symptoms
Pain under or around the knee cap
Pain is often worse after activity that involves knee bending - running, stairs, squats, etc.
Knee 'cracks' or needs to be cracked to decrease pain.
Patient cannot sit for long periods of time without straightening out the knee to make it crack. This is called 'Theatre Sign' - patients must sit in an aisle seat at the Theatre so that they can straighten out their knee frequently.
What's Going On
The cracking that is often associated with PFS is the sound of the patella clunking back into it's groove. Pain is often aggravated by bending because this causes the most motion of the knee cap over the femoral groove.
For whatever reason, the lateral muscles of the thigh have gotten tighter or stronger than the medial muscles of the thigh. This may be due to a problem with the feet such as over-pronation or fallen arches, or it may simply be due to the muscle's natural response to an increase in training.
What To Do About It
If there is an underlying problem with the feet, that's something that should be addressed by a professional. It may, however, be as simple as changing running shoes. If the muscles are at fault you should be able to remedy the problem with a home stretching and exercise routine. Massage may also prove useful as a means of loosening up the tight outer quad muscle.
Here's what you can do for yourself, in a nutshell:
Stop the aggravating activity. Fitness can be maintained with activities that don't cause pain.
Stretch the quads. Tight muscles are often at the root of PFS. See stretching for details.
Use ice over the knee when pain is severe
Home exercise involves strengthening the quads through a specific progression of exercises. You begin with exercises that don't involve much, if any, bending of the knee. As the condition improves, bending exercises can be added.
Begin with 2 exercises that don't bend the knee much. The first is called Straight Leg Raising. Lie on your back (you can rest on your elbows if you like) and raise the affected leg up off the ground, keeping the leg straight at all times. Focus on flexing the quad muscles. Repeat this movement 10-15 times. Rest and then repeat again. Once this becomes too easy, you can add ankle weights if you have them, but that's not mandatory. The second exercise is called Quad Setting. Sit with your legs straight out in front of you. Take a pillow or roll up a towel or two and place it under your knee. This should put a bend in your knee - maybe 20 degrees. Now push down with your leg, trying to straighten out your knee. You must have a thick enough pillow or towel under your knee to prevent it from straightening out. You also have to try to concentrate on contracting the quad muscle, not the muscles in the back of your thigh. Repeat this movement 10-15 times. Rest and then repeat again
Once you've been able to do these exercises daily for about 2 weeks, and if you feel like you're improving, you can add some new ones. Begin with some isometric exercises. These involve flexing the quads but not moving through a range of motion. Sit on a chair or bench, facing a wall. Your legs should be at 90 degrees with your toes up against the wall (wear shoes!). Now, push into the wall with your legs, flexing your quads but not moving through a range of motion. Hold 10 seconds and relax. Repeat 10-15 times. You can do the same with your legs extended straight out in front of you, if you can find someone to push down on your feet. Flex your quads and keep your legs straight.
As you improve, the addition of exercises that increase range of motion, such as leg extensions, can be added.
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