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One of the most common injuries I see in runners is knee pain due to poor alignment of the kneecap (patella) on the thigh bone (femur). This type of knee pain, located around the kneecap, is called patellofemoral syndrome. One of the most significant reasons for the poor alignment of the kneecap is an imbalance in strength and flexibility of the muscles which attach to and control the movement of the kneecap.

The kneecap sits in a groove on the thigh bone, much like the way the wheel of a train sits on a track. If the wheel on the track sits upright, it will glide smoothly along that track. If the wheel is caused to tip or shift to one side, it will grind against the track. Our kneecap works in a similar fashion. If the patella shifts or tips it can grind against the femur and irritate the cartilage on the back of the patella, which may result in pain with associated running, walking and ascending and descending stairs. People may also notice pain after sitting for prolonged periods of time when they attempt to stand and walk.


The large muscle group which sits above the knee cap is called the quadriceps, see the figure above. The quadriceps play an important role in the motion and control of the knee. It is designed to straighten the knee, thus it is working with every step we take. The quadriceps has four parts to it: an outer part called vastus lateralis, an inner part called vastus medialis, and two central parts, which lie one on top of the other called rectus femoris and vastus intermedius. These four parts of the muscle work to keep the kneecap positioned properly in the groove on the femur, just like the wheel on the train track. If one part of this muscle group is weak or another part is too tight, the kneecap can shift or tip. The scenario that I see most often is that the vastus lateralis is more developed than the vastus medialis. The muscle imbalance results in the kneecap shifting towards the stronger side thus lying on the outer part of the groove on the femur. Compare this to a game of tug of war, with the big strong players on one side and the weaker players on the other side; the stronger team can pull the weaker group over to their side. Other common factors that cause this tug of war scenario include tightness of the iliotibial band, weakness of the gluteal muscles or hip adductors or tightness of the retinaculum around the kneecap. Thus a thorough assessment is required to determine exactly which structure is a fault.

The positive side of this problem is that it can be successfully treated once it is determined which structures are at fault. By correcting the short or tight structures with proper stretching and strengthening the weaker muscles, proper alignment of the patella can be restored and the pain can be diminished. Treatment may also include modalities such as ultrasound, designed to reduce inflammation around the patella and muscle stimulation, designed to re-educate the weak muscle to do its job properly. In addition, the patella can be taped into proper alignment to help facilitate the patient in learning where normal alignment is and what it feels like. Other areas such as foot and pelvic alignment are also examined to determine if there is any other underlying factors above or below the knee which may be putting undue stress on the knee.

With proper assessment and treatment the proper muscle balance can be restored and the runner can return to their sport pain-free and with improved alignment they can enjoy their sport even more. If you require further information on this topic, please contact us at the clinic at 752-9926.

Cynthia MacDonald, BScPT Physiotherapist