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07 June 2010 ~ 1 Comment

PFS/”Runners Knee”- What is it?

Over the past few blog posts we’ve been tying up some loose ends. In the first nine installments, we moved through all of the major joints of the legs, including the hip, knee, ankle and foot. During these posts we identified and demonstrated self muscle massage techniques that you could use on each muscle group (if you missed any of the series or would like to review it, click here). We then took a look at the modifications you might make to these techniques in an acute versus chronic/repetitive overuse injury situation. Now we’re going to get a little more specific and talk about some popular overuse injuries that endurance athletes face.

First up is knee pain (also known as patellofemoral syndrome, PFS, or “runners knee”). This would refer to pain that is around the knee cap (usually on the inside just below it and on the outside just above it). In addition to pain, other symptoms include swelling, clicking, popping and creaking. PFS comes on gradually over time and is worse after rest (sitting for long periods of time and then standing up for example). During activity, symptoms typically start out as an ache/tightness and worsens as exercise continues. Another classic example is pain/creaking/clicking going up and down stairs.

Traditionally, there are two main types of PFS:

1) Symptoms due to abnormalities in the bone. This would include different shapes in the knee cap itself or the groove that it rests in on the femur (long thigh bone). Due to the differences in bony surfaces, inflammation and breakdown of the bone can occur.

2) Symptoms due to muscular restrictions and imbalances. This would include symptoms caused by tight muscles pulling the knee cap out of its normal groove. It also includes symptoms caused by tight muscles pulling the knee cap down tight over the bone so that it grinds or catches, causing inflammation and over time breakdown of the bone.

For this blog post, we’ll be focusing on PFS that is the result of muscular restrictions and imbalances. Proper diagnosis and detection of bony abnormalities is best left to evaluation by your health care team. That being said, if you are experiencing knee pain in conjunction with buckling, locking and painful clicking, it is strongly recommended that you schedule an appointment with your orthopedic for a full workup.

Why does Runners Knee occur??

During normal walking and running, your leg must accept the weight of your body during initial contact with the ground. This impact is absorbed and then transmitted up the leg as you move your body weight fully onto the leg (also known as mid-stance). This momentum is then used to propel the body forward during heel and toe off so that your other leg (which has been swinging forward) can repeat the process all over again as it comes into contact with the ground.

Sound confusing?? Here’s a different way to look at it and the muscles that are involved:

Phase 1) Shock absorption as the foot lands and the leg then straightens to support the full weight of the body = Quads

Phase 2) Moving the body forward over the weight bearing leg = Hamstrings + Glutes

Phase 3) Final push-off = Calf

If there are any hitches or restrictions in the muscles that provide this sequence, other muscles must compensate to maintain forward motion. Essentially, this is what causes “runners knee”. If forward propulsion is interrupted or shortened either at the ankle or knee, the result is a shortened stride that uses the hamstrings and adductors to pull through (instead of the larger glute muscles that are supposed to do the job) and the quads for everything else. With this increased load on the quads (now they have to shock absorb and push off), it is very common for the increased strain on the muscle to affect the knee cap, causing pain and irritation as it gets pulled from it’s normal bony groove.

Here’s a visual of what I mean:

The picture above represents the final phase of push off. The hip is fully extended, the knee is straight, the ankle is pointing down and the big toe is extended. From this point, the ankle fully points down as the calf engages, the knee bends, and the leg can begin it’s swing (typically the force of push off causes the knee to bend enough that the heel comes up towards your butt….this is a major difference between elite level and beginning runners).

To reach this phase you must have the following. Without them, there is an increased risk for compensating muscles breaking down under the added strain:

1) Full hip extension. This can be limited by tight hip flexors or weak glutes.

2) Full knee extension. This can be limited by tight hamstrings or calf muscles (remember- both cross the joint behind the knee. restrictions will result in a slight being present at all times.)

3) Full ankle mobility. Prior to heel off (pictured above), the body must come fully over the ankle while the foot is flat. Restrictions in the calf muscles or foot itself (flat feet/low arches for example) will limit this.

4) Full big toe extension. To truly get the most power from push off, full toe extension is required. If unable to bend your big toe back all of the way, heel off will be limited and the stride shortened. This is often the case with arthritis and bunions.

Differential Diagnosis (How do I know if it’s PFS or something else entirely???)

One of the main reasons that PFS (especially when the cause is muscular versus bony) is challenging to treat is because there are multiple things pain around the knee cap might be (these are also known as differential diagnoses).

#1 Quadriceps Tendonitis- This refers to the area directly above the knee cap where the quad muscles become tendon at the top of the knee cap. Very common for this area to get injured due to acute trauma and also due to repetitive overuse. With this injury, pain is directly on the tendon and the tendon itself may be tender or swollen.

#2 Patellar Tendonitis- As the common quad tendon crosses the knee joint, the knee cap actually sits inside of it. The tendon that then connects the knee cap to the lower leg bone (the tibia) is called the patellar tendon. Like the quad tendon, it is a very common area to get injured due to acute trauma and also due to repetitive overuse. With this injury the pain is directly on the tendon and the tendon itself may be tender or swollen.

#3 ITB (Iliotibial Band or IT band)-

One of the easiest ways to differentiate PFS from ITB is to look at where it is. The ITB runs down the outside of the knee and inserts onto the fibular head (little lower leg bone on the outside of the leg). If your symptoms are at the level of the knee cap but are behind it looking from the side, it is more likely that your problem is ITB related versus PFS.

If you think that your symptoms may be one of these three examples, check back on our post about tendonitis for some tips on how modify your muscle massage techniques to best treat it. You will also find guidelines to assist with pain and swelling.

In the next post on Runners Knee, we’re going to discuss how to treat it. As always you can join us on Facebook to join the discussion on each weeks post or you can leave a comment below.

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