Several studies of athletes have demonstrated that knee injuries, including anterior knee pain and patellofemoral pain syndrome, are the most common overuse injuries evaluated in sports medicine centres across the world.
Further to this, it is well documented that knee pain is the most common lower-extremity overuse problem in cyclists. In one recreational long-distance bicycling tour, 65% of all riders reported knee pain.
Another reputable study of more than 500 recreational cyclists indicated that almost 42% of all riders experienced overuse knee pain. While major problems such as fractures, dislocations, and ligament ruptures usually occur only after major trauma, overuse injuries are much more common.
Injuries such as this may also be related to improper bicycle fit or equipment, poor technique, or inappropriate training patterns. Cycling is very repetitive; during only 1 hour of cycling, a rider may average up to 5,000 pedal revolutions. The smallest amount of misalignment, whether anatomic or equipment related, can lead to dysfunction, impaired performance, and pain.
The Patellofemoral Joint:
Patellofemoral pain syndrome, also called retro patellar pain syndrome, refers to anterior knee pain emanating from the patellofemoral joint and supporting soft tissues. The patellofemoral joint being the articulation between the kneecap and the femur or thigh bone.
In overuse cases, the cause of the damage is usually repetitive rubbing of part of the cartilage of the under surface of the knee cap against the underlying thigh bone.
In a healthy knee the movement of the Patella across the knee is a gliding, smooth movement. In individuals with Patellofemoral pain syndrome, the knee cap rubs against the part of the joint behind it, resulting in inflammation, degeneration and pain. This can be for a number of reasons, but is usually due to the position of the patella itself.
The most common feature of patellofemoral pain is patella mal-tracking. The patella most commonly runs too laterally (to the outside) in the groove. This problem is most regularly caused by muscle imbalances, where the lateral quadriceps muscles and other tissues such as the retinaculum are too tight and the vastus medialis oblique muscle is weak.
To put all of this in English, basically the function of the knee cap is to enhance the lever arm over which the quadriceps can better impart their force into moving the lower aspect of the leg. The knee cap should ‘float above’ the groove in the femur to allow this to happen in a pain free way. It is held in place to allow this float by a medial contraction of the Vastus Medialis Oblique (VMO) muscle, or that big tear drop shaped muscle that is prominent on the inside of the thigh, and a lateral contraction of the gluteal muscles acting on the Illio-tibial band (ITB) that runs from these gluteals in your buttock, down the outside of the thigh and inserts into the outside of the knee cap.
Their contraction should be balanced and occur in a synchronised manner merely locking the kneecap in place.
The flaw with this is several fold in cycling:
Problem one is that cycling naturally tightens and strengthens the glutes and therefore ITB, thus resulting in a greater lateral component of pull.
Problem two is that despite what many people would naturally believe, cycling does not, as effectively as it would seem, strengthen the VMO as much as it strengthens other quadriceps muscles thus resulting in a reduced medial pull.
Problem three is that any slight biomechanical flaw in technique or load directly effects and tightens the lateral structures producing more lateral pull.
Problem four is that any even mild knee pain results in an inhibiting effect of the VMO thus reducing the medial component of pull further and thus increasing pain further.
The upshot of all of this is that any given cyclist faces an ongoing battle to maintain correct patella alignment and thus prevent knee cap pain. Should you then get knee cap pain the inhibiting effect on the VMO produces an ever increasing downward spiral!
Thus the battle against this pain and its onset must start before training even commences. A pre training bike set up to identify and reduce mechanical disadvantages, a correctly managed training build up to prevent over load pain and an ongoing stretching plan to alleviate and slow down the inevitable tightening of lateral structures, unfortunately normal in the loading pattern of cycling!