Written by Marie-Catherine Bruno, BScPT, Cped(C).
When I first heard of the runner’s knee, I thought it was a new pathology that I had never heard of! Being a specialist in sports medicine, I could hardly believe it, so I pushed the research a little further only to realise that it was nothing else but the good old Patellofemoral Syndrome (PFS) (also known as Patellofemoral Pain Syndrome – PFPS). Patello stands for patella, which is the Latin word for the knee cap. Femoral refers to the femur (your thigh bone), and Syndrome means a group of symptoms. So basically, PFS is a generic term for any disorder/pain that affects the joint composed of the knee cap and the femur. Very generic.
Usually, the problem is flared up by too much friction in the joint, creating some irritation that soon becomes a source of inflammation. In most cases, it gets progressively worse if not treated. It can also turn into a chronic problem and create permanent damage to the joint.
The symptoms of Runner's Knee
Pain is definitely the first warning sign. Since PFS is a mechanical problem, it will normally be exacerbated by movement and sports (as opposed to chemical problems that are actually relieved by movement). The first manifestation usually occurs after a longer than normal training session (like a long hike, a long run or even a long ski) or simply a harder session. The pain is typically located around the knee cap, or directly under. It is usually described as a dull ache or pressure, but can sometimes create very sharp pain with certain movements (like going down stairs or doing squats). The pain will usually disappear with rest for a few minutes or hours. It never irradiates further than the knee joint itself.
As the problem gets worse, you may experience what is called the theatre sign, which is exacerbated by sitting for a long period of time (hence the name!) or simply working at a desk. Because PFS has very similar symptoms to a torn meniscus (or cartilage), the theatre sign is a very good way to help your doctor differentiate between the two: meniscus does not get aggravated by sitting only (unless you cross your legs, but that is a whole different story).
The Causes of Runner's Knee
As mentioned earlier, it is usually a friction problem in the joint between the femur and the knee cap. Bones are covered in cartilage in joint areas in order to allow for good gliding against each other. The whole joint complex is also covered by a membrane called the synovial membrane, which contains some liquid that keeps the joint lubricated. If any of the above structures fail or get damaged or stressed, then you may encounter a friction problem. All of the following can potentially increase the level of friction at the patellofemoral joint:
- Tight Quadriceps or Iliotibial band (ITB): both those muscles have fibres that cross over the knee cap and attach below. When they are too tight, they put more pressure on the knee cap by pressing it down against the femur (imagine running with someone’s hand pressed against your knee cap). That increases the pressure in the knee and creates friction in the joint. In the long run, this may even wear out the cartilage (which does not regenerate by the way), and further lead to osteoarthritis (OA).
- An out-of-alignment knee cap: the femur has a groove in which the knee cap (patella) sits. The patella should sit properly in the groove and match it like the piece of a puzzle, otherwise you get movement where the bone is not covered in cartilage (bone on bone friction) and also get areas of no contact between the two bones which leads the cartilage to dry out. This creates a lot of inflammation, and can wear out the cartilage and bone. Your patella may lose its proper tracking due to the following (figure 1 demonstrates how the axis can get disturbed):
- Muscle imbalance: the muscles on the external side of your thigh - Vastus Lateralis and ITB - have a tendency to become stronger than the internal side – Vastus Medialis and adductors - dragging the patella away from the groove.
- Muscle tightness: if one side of your thigh is stronger than the other – see muscle imbalance above – or if you favour that side then the chances are that it is also tighter, and it is dragging the patella out of the groove.
- Congenital bone malformation: for some odd reason, the groove and the patella may not have been designed to match – not much you can do about that one!
- Falling arch in your foot: this creates an internal rotation of the rearfoot that drags the tibia and even sometimes the femur. Your patella then sits on a diagonal line to adapt to all that.
- Wide hips (guys, go ahead and laugh at this one as it is probably not affecting you!). But women in general have wider hips than men. Wide hips change the angle of the legs and make them rotate in a little bit – looking like the knees are staring at each other. This postural adaptation unfortunately leads to muscle imbalance and tightness and makes women more prone to PFS than men.
- A smaller than normal patella (micro-patella): women have in general a smaller patella than men, in relation to the size of the femur. Looking at the physics of pressure, a smaller surface (the patella in this case) will create greater pressure for the same amount of force on a stable surface (the femur). This means that people with a smaller patella have more pressure in the joint, making them more prone to develop a friction and overpressure problem.
- Wearing a knee brace/support: many runners have been prescribed some sort of a knee brace to either support the knee in some way, or simply to keep the joint warm. Be very very careful, because those can create more damage than do you good. The worst ones are the ones that totally wrap around the knee and not have a hole (commonly called a doughnut!) to free the patella. They put a lot of pressure on the knee cap. The ones with a doughnut are okay only if worn and fitted properly: make sure that the hole is big enough to clear the entire patella (the sides of the doughnut should not in any way touch the patella) and that it is centred enough to let the patella move freely, otherwise you are heading for a friction problem! Note: these braces are usually overly prescribed and too many people have became dependant to them. Unless they have some serious strapping around the knee cap to permit changing its position, they are usually only effective against patellar dislocation.
- Chondromalacia: this is a disease of the joint that basically turns your cartilage into Swiss cheese. The bones then cannot glide as easily and the joint becomes chronically inflamed. (This disease can only be confirmed by arthroscopy, i.e. going in the joint with a mini camera – overly wrong diagnosed in North America, I ignore what the situation is in the rest of the world.)
The diagnosis of Runner's Knee
As mentioned earlier, the name Patello-Femoral Syndrome is used to describe a plethora of knee cap problems. Be aware of health practitioners that diagnose you with PFS; many of them use it when they do not know exactly what is going on with your knee. Unless you have been having problems for over 10 years, your X-rays will more than likely be normal (cartilage does not show on X-rays, therefore the damage to it cannot be seen), so it cannot be diagnosed based on an X-ray only. Arthroscopic image may be the only positive test, but again, doctors will usually use this test to make sure that your meniscus is intact. The only way of really making a good diagnosis in the case of the PFS is a good physical exam.
The Treatment of Runner's Knee
- The first thing you must do is to control the inflammation. There is so much friction in your knee that is it probably getting constantly irritated. Anti-inflammatory herbs or medications may help, but their effect is usually not very precise. To reduce the inflammation you will probably get better results with ice (about 15 minutes, wrapped in a wet towel) and physiotherapy (ultrasound, laser and micro-currents are effective against inflammation). Your nest step is to work on the cause and get rid of it.
- For tight Quadriceps and ITB, nothing more simple : get on the stretching program and relieve that pressure on your knee cap.
- For muscle imbalance and tightness, I recommend a good exercise program to target the weak muscles (Vastus Medialis and adductors usually) and to stretch out the tight ones (ITB and Vastus Lateralis).
- You will also need some Myofascial Release (MFR) around the knee cap because the soft tissues have probably already adapted to this malposition of the knee cap. This type of work can be done by a registered massage therapist (RMT), an osteopath or a physiotherapist (if not taken care of, your injury will take a lot longer to heal, and will have a tendency to be recurrent). A common technique also used to improve the alignment of the patella is called the Mc Connell Taping Technique. Ask your physiotherapist about it.
- If you are suffering from a micro-patella, then you can only limit the damage by keeping your muscles very flexible and balanced (this will release some of the pressure in your joint) and make sure you keep the inflammation away (ice after every workout).
- Your hips are wide or you have falling arches? Then make sure that you get on a stretching program to improve your posture and avoid muscle tightness. You probably need orthoses (custom insoles). You should also see a postural therapist if your knees are looking at each other.
- You usually wear a brace? Make sure you really need it. Reassess the need for it by getting a second and even a third opinion from another doctor or brace specialist.
Once the inflammation is under control (you should not see any swelling left around the knee cap), and you are getting rid of the cause, then you can start exercising again, but very gradually. Listen to your body, it usually knows what it needs.