- Dr. Lee Brotherston
Cycling and knee pain - the hips don't lie
Part 2 in a multi-part series on cycling and staying healthy.
In part 1, we discussed low back pain, and how some simple core endurance exercises could decrease your back pain while cycling, and increase your fun. We will update that post in the future with some other areas to consider when dealing with cycling related back pain. Today, however, we are going to delve in the knee – more specifically, how problems at the hip can impact the knees. Much like the back, the knee is a complex region that if often the victim of overuse cycling injuries. Lets start with some anatomy.
The knee joint is the largest, and most superficial, joint in the entire body. The bones that make up the knee are the large femur (your thigh bone), tibia (your shin bone), and the patella (your kneecap). The fibula serves an important role as an attachment site for muscles and ligaments, but it isn’t directly involved with the knee joint. The knee functions primarily as a hinge, that is, it flexes and extends. However, it isn’t purely a hinge motion. As we flex/bend the knee, the tibia must glide backwards on the femur in order to remain congruent (in contact with the femur, providing stability). There is also some rotation that occurs between the femur and tibia.
As you can see from the picture above, the knee doesn’t have much mechanical stability (compare it to the hip joint which has a ball and socket orientation, and is therefore very strong), thus, it gets its strength from the muscles and ligaments surrounding the joint. This lack of mechanical stability means the knee is at the mercy of the other joints in its kinetic chain – the hip and the ankle. What this means, is that dysfunctional movement at the ankle below, or the hip above, will translate to abnormal forces on the knee. We can compare the lower limb kinetic chain to the proverbial chain, and the knee is the weakest link. Aside from obvious traumatic injuries, rarely does the knee suffer an injury that isn’t a result of an aberrant movement somewhere else in the chain.
If you think of the force transmission in cycling, the forces are transferred from the rider to the bicycle by way of the femur, tibia, foot and shoe/pedal interface. The majority of cyclists I know, and nearly all elite cyclists use a clipless system (a misnomer, I know, but it means the pedal is physically clipped to the shoe via a cleat on the shoe) Therefore, the foot is fixed to the pedal, and the head of the femur is solidly supported in its socket. This means the knee can be vulnerable to unwanted rotation, as well as compression on the inside or outside of the knee. The picture below demonstrates this, and is referred to as either Genu (meaning knee) valgus or varus.
As you can see in the middle picture, the knees are bowed outwards (genu varus), and if you look closely, you’ll see it’s the inside portion of the femur and tibia making contact with one another, meaning there is excessive force being placed on the inside (medial) portion of the joint. With the picture on the right, the knees are close together with the feet spread apart (genu valgus). This will place the outer (lateral) portions of the knee joint under increased stress. Now, when we talk about genu varus and valgus, we are usually talking about a congenital issue – the bones are actually formed in such a way that this position is the normal position for that individual. However, with muscle weaknesses or imbalances we can have abnormal positioning of the bones during movement. These imbalances and weaknesses are what we need to address.
Improper lower limb mechanics can commonly be seen in cyclists when you view them head-on while pedaling. As the knee flexes and you’re at the top of your pedal stroke and beginning to apply power to the cranks, your knee may brush the top tube of the bike. This is due to internal rotation at the hip joint. This not only decreases efficiency, it can lead to knee pain as the lateral structures of the knee are compressed, and the medial structures are stretched. What can you do about this? Well for starters, be conscious of the movement, and understand that you want your knees to remain pointing straight ahead. Often, there isn’t an actual muscular problem, but rather a habitual problem. If you find you fatigue easily, and can’t keep your knees from brushing the top tube, then we need to consider strengthening the hip abductors and external rotators, as well as do some core stability and endurance exercises.
Read enough articles about reducing injury in athletic populations and you’ll notice how important core endurance is. Go back and read the first post in this series to find out more about core endurance. Once you’ve done that, come back and try this: Stand in front of a full-length mirror. Place your feet at a distance apart that mimics standing on pedals. Bend one knee and bring that foot off the ground so that you’re now standing on a single leg. Squat. What happens? Did your support knee move inwards during the squat, or did it stay in line with your toes? If it was the former, try it again, but this time be aware of what you’re doing. Try to keep your knee pointing straight ahead. If you cannot do this, we need to take a step back. This time, perform a lunge and try to ensure that the knee remains inline with the toes.
If this is still too hard to do, then a good place to start is with some side-lying abductions/leg-raises. To begin, lie on your side and make sure your hips are perpendicular to the floor. Then, lift the top leg up, as shown in the picture below. Once this is mastered, try the same exercise, but in a side plank position. Research shows that this exercise has the highest maximum voluntary isometric contraction (MVIC) for gluteus medius, at between 89 and 103%. In other words, it’s a very effective exercise for targeting gluteus medius – a strong hip abductor and stabilizer.
To recap, the knee is the prisoner of the hip and ankle. What happens above and below the joint, ultimately dictates the amount of forces and going through the knee, and where that force is concentrated. Be aware of faulty movement patterns and try to consciously correct them. Target the muscles of the hip complex by performing squats, single leg squats, and lunges. Target gluteus medius specifically, by performing side-lying leg raises, or best of all, side plank hip abductions (side-lying leg raises while in a plank position). Next time we will discuss the foot and ankle, and their role in knee pain and cycling. If you have any questions or would like to learn more, contact us, or book in for an appointment and we can help identify any issues and give you the tools to fix them.
Thanks for reading,
Dr. Lee Brotherston
Oak Ridges Health Group
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