Cycling is a highly repetitive sport, with a rider averaging about 5000 revolutions per hour of cycling, making overuse injuries of the knee commonplace amongst cyclists. The smallest amount of mal-alignment and incorrect distribution of load, whether anatomic or equipment related, can lead to dysfunction, impaired performance, and pain.
Overuse injuries occur when a tissue accumulates damage caused by repetitive submaximal loading. Repetitive activity fatigues a specific structure, such as ligament, cartilage, tendon or bone. Without adequate recovery, microtrauma stimulates an inflammatory response that can damage local tissue. Cumulative microtrauma from further repetitive activity eventually leads to clinical injury. In chronic cases, this continued process can result in degenerative changes that lead to weakness, loss of flexibility, and chronic pain. Thus, in overuse injuries, the problem is often not acute tissue inflammation, but chronic degeneration.
Anterior knee pain and patellofemoral pain syndrome are among the most common leg overuse injuries in cyclists. Injuries may be related to improper bike fit or equipment, poor technique, or inappropriate training patterns. Patients generally report that the pain is worse when the knee is loaded e.g. when climbing or descending stairs, during prolonged sitting or squatting, when climbing hills or pushing high gears. Chondromalacia, Quadriceps tendinosis, and Patella tendinosis are other conditions which can result in pain at the front of the knee and result from similar factors.
This condition has been referred to as “Spring knee”, as it often rears its head with the onset of Spring, when the sun starts to shine and cyclists come out of hibernation! Either that, or they realise they should probably start training for that summer sportive they have entered, and hit the roads with too much vigour.
Some of the contributing factors in developing this type of knee pain include:
Most cyclists' quadriceps and hamstrings will tighten with prolonged riding due to the repeated contraction and shortening of these muscle groups. Inflexibility of the quadriceps, hamstrings, or iliotibial band (ITB) may restrict range of motion around the knee and are likely to increase the forces on the knee.
Weak Leg Muscles
May lead to fatigue-induced alterations in pedalling technique, which will also alter the forces on the knee. As muscles fatigue, their ability to take load decreases, increasing forces through the joint.
Poor activation of the inside quad muscle (VMO) and/or tightness/overactivity of the outside quad muscle (vastus lateralis) and ITB can alter patella tracking, increasing load though one part of the knee.
Include heavy training loads and high mileage (beyond what the body is conditioned to do), or a rapid increase in training distance or intensity, especially hill work.
Gearing and Cadence
Pushing hard gears at low revolutions puts high load through the patella, whereas lower gears at a high cadence (85-90rpm) will put less load through the patellofemoral joint with each stroke.
Inside drift (internal rotation) of the knee, especially during the push down phase (and when they are tired) can be due to weakness of the gluts or inside quads muscle (VMO). This increases the lateral forces on the patella.
May be too low, too far forward, or both, causing excessive patellofemoral loading throughout the pedal cycle. When the saddle is low, the knee functions in hyperflexion, increasing compression of the patella on the femur.
Improper shoe cleat position or float may force the rider to pedal with poor biomechanics, increasing patellar forces. Cleats with excessive internal or external rotation may cause exaggerated tibial rotation, placing more stress on the anterior knee.
To treat and prevent “Spring knee”, you need to alter the amount of load going through your patella and surrounding tissues. Your Physiotherapist will be able to assess what is tight, weak, or simply not working properly, not only around your knee, but also around your foot/ankle, hip, pelvis and trunk, and design a program to address these issues. A cycling-savvy therapist will also be able to give you advice on training, technique and help you identify when you should rest or push on.
Finally, a comprehensive bike fit is essential, looking at the 3 points of contact – saddle, handlebars and foot/pedal – and all the variations of. The saddle (height, fore/aft, tilt, type), shoe (insoles, wedges, size, width, heel support), cleat (position, float), crank length, and handlebars (reach, height, angle, levers) all need to be addressed, and finding the right balance between comfort, efficiency and injury with so many variables involved, takes the skill of an experienced bike fitter!