Knee pain in cyclists: What causes it and how to fix it

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Knee pain is one of the most common overuse-type injuries that cyclists can suffer from. In a survey of 109 professional cyclists, nearly a quarter (23%) reported having knee pain in the last 12 months. Of those 22 knee injuries, 13 were serious enough to cause time off the bike.

Recreational cyclists actually fair worse. In a Californian cross-sectional study involving 518 cyclists, 41.7% reported knee injuries, with a low level of cycling experience being associated with increased prevalence.

In a sport that involves no impact forces (providing you don’t fall off), and a very predictable pattern of movement, these percentages seem high. It may be the repetitive nature of cycling that’s responsible for causing problems, however. If you consider that riding for an hour at 90 rpm will involve 5,400 pedal revolutions, you can begin to see how minor issues can become major ones relatively quickly.

In this post we’ll focus on the likely causes and solutions to the most commonly reported knee issue, patellofemoral pain syndrome or PFPS. Even if you’ve been diagnosed with other forms of knee pain such as Iliotibial band friction syndrome (ITBS) or patellar tendon issues, read on because there will be some crossover in both the likely causes and the solutions.

Brief anatomy of the knee

The knee itself is a very stable joint with strong collateral ligaments either side and two cruciate ligaments to guard against forces from the front and back. The knee is actually formed of two joints: one between the femur (thigh bone) and the tibia (shin bone) called the tibiofemoral joint; the other, which is of particular interest to us, is the patellofemoral joint. This consists of the patella (knee cap) and the femur. The patella runs in a shallow trough on the front of the femur called the trochlea groove. It’s this articulation that gives the joint its name.

Image: Wikimedia Commons

The patella’s main role is to act as part of a pulley system to increase the effectiveness of the quadriceps muscle group. It attaches to the quadriceps via the quadricep tendon at one end and to the tibia via the patella tendon at the other.

What is Patellofemoral pain syndrome (PFPS)?

PFPS describes pain coming from the area around the front of the knee or behind the patella. As a result, the condition can also be called anterior knee pain.

Just to confuse the matter further, you may also see it called runner’s knee. As you might expect, this is in reference to the large number of runners who suffer from the condition. Much like tennis elbow you don’t need to be a runner to have PFPS.

It’s thought that pain arises when the knee tracks poorly within the trochlea groove. A bit like a train coming off its tracks ever so slightly, every time you bend and straighten the knee.

Causes of Patellofemoral pain syndrome

There is no one definitive cause of PFPS but several have been strongly associated with the condition.

Bike fitting

The height of the saddle and both forward and backward positioning have been found to influence the forces at the knee. For the sake of this article however, I’m going to presume you have this one covered. If you would like further information on bike fitting, here are a few articles that might help.

Training errors

So common is this likely cause that it has a special name all of its own: ‘spring knee’. Named after the time of year that most cyclists begin to increase both their mileage and training intensity, it’s caused by an inability of the muscular system and its associated tendons to adapt quickly enough to the demands imposed.

The standard recommendations are that you should increase your mileage by no more than 10% a week. Of course, few people do that, especially here in the UK when the sun comes out (yes, it does happen).

Muscles and tendons in particular take time to adapt to load. If the demand is too great, then the damage caused by the activity doesn’t have time to repair and a downward spiral ensues. The tricky part is deciding exactly where that line is. It will be different for everybody and doesn’t necessarily fit within the generic 10% guidelines.

Other stresses

Remember as well that cycling is just one form of stress you are applying to your body. Psychological stresses from work and family life, for example, also play a role. Studies have shown the amount and quality of your sleep alone can have an influence on your susceptibility to injury.

Biomechanical influences

Whilst your general health status may be of significance, hopefully you only have pain in one knee. This has led researchers to investigate what might be different in cyclists on the injured side.

In a study of 24 cyclists, 10 with a history of anterior knee pain and 14 without, researchers noted that subjects with previous knee issues adopted very similar pedalling styles on their injured side. Interestingly they all displayed an inward movement of the thigh (adduction) towards the top tube and an outward movement (abduction) of their lower leg during the downward pedal stroke.

The authors also noted a significant increase in ankle dorsiflexion (the top of the foot moving towards the shin) on the previously injured side. In particular during the knee flexion portion of the pedal stroke.

It’s obviously impossible to know if this altered pedalling style was the result of injury, or the likely cause of it. What is clear however is that adduction of the thigh may disrupt the function of the quadriceps and potentially cause problems at the knee.

Imagine the knee dropping inwards during the lifting phase of a squat for example. Now think about that happening 5,000 times in an hour and you can see why this might be an issue. Other studies have also focused on the position of the knee.

Altered muscle activation

This study looked at whether cyclists with PFPS used their muscles differently compared to heathy controls. There is a theory that of the four quadriceps, the one closest to the outside of your leg — the vastus lateralis — may be responsible for pulling the patella out of its groove on the front of the femur and contributing to PFPS. Whilst the researchers did find the vastus lateralis was marginally more active in subjects with PFPS, the biggest differences were noted in the hamstrings.

You have three hamstrings. Two attach on the inside of your tibia — the semimembranosus and semitendinosus — and one attaches on the top of your fibula (calf bone) — the biceps femoris. The hamstrings control both knee flexion and medial and lateral rotation1 of the tibia. Think of them as the reigns on a horse, with the tibia being the horse. If the medial (inside) hamstrings contract they will cause internal rotation of the tibia. If the lateral (outside) one contracts, external rotation will occur.

Image: Springer

The researchers found biceps femoris (the lateral one) to be more active in the cyclists with PFPS and semitendinosus less so. This is interesting because external rotation of the tibia has been linked to an increase in pressure on the lateral aspect of the patella in all positions of knee flexion. This may go some way to explain why these cyclists were experiencing issues.

Hip weakness in cyclists with PFPS

While I’m not aware of any studies looking at hip weakness in cyclists with PFPS in particular, a number have investigated this as a potential contributor in other populations. Most have found weakness in both the hip abductors (the muscles that take the leg out to the side) and the hip external rotators.

It’s not a huge leap to presume that a more adducted femur, such as those found in cyclists with PFPS, may in part be due to weakness in the muscles that control that motion: the hip abductors.

In a study on cyclists suffering from ITBS, researchers found strengthening the gluteus medius muscle (a hip abductor) to be effective in reducing pain. Whilst not the same issue of course, the biomechanical variations that lead to ITBS are comparible to PFPS. Most notably the increase in femoral adduction.

Exercise solutions to PFPS in cyclists

With the research in mind, let’s take a look at exercise solutions to help you recover from PFPS. What you’ll notice is that all of the following solutions require gym equipment. That’s because strength training equipment provides you with the fastest and safest route out of your situation. A home-based exercise programme may not cut it for three key reasons:

1. You can’t effectively isolate weak muscles and therefore you give your body the opportunity to compensate around these areas. This will impact your results.

2. The loads you’re able to apply are sub-physiological. Once you can do 20 bodyweight squats for example, then what? 25? This won’t stimulate further strength gains.

3. Creating adaptation within the muscle is about applying a progressively heavier resistance. Strength training machines account for this by offering you small increments in weight.

The four key exercises to help you recover from PTFPS.

Follow the guidelines for each exercise carefully and use both a light weight and a slow repetition speed to begin with.

I instruct most of my clients to start with a 12-second repetition. This includes a five-second shortening phase (concentric contraction), a one-second pause at the end of the range, and a five-second lengthening phase (eccentric contraction) with a further one-second pause before beginning again. This process ensures the forces on the joint are minimised but the stimulus to the muscle is maximised, which is exactly the combination we’re looking for at this stage.

Choose a weight that you can complete 6-8 repetitions with at that speed. One set is fine to start.

If you feel pain, stop and assess. Is the exercise set up correctly? Where in the range of motion do you feel the pain? Can you work within your pain-free range of motion for the moment?

If, for example, you feel pain as you approach the fully extended position of the leg extension, stay out of that position for the moment. Work within the range that feels good and revisit that position in a week or so.

Leg extension machine

When injury strikes, muscle weakness will inevitably follow, especially in the area of the injury itself. The strength of your quadriceps will likely have been affected by your injury and may even be one of the reasons for it. As a cyclist you need strong quadriceps. There is no better machine to strengthen these in isolation than the leg extension.

Use the following guidelines to maximise your safety and results:

– Make sure your knees are in line with the axis of the machine.
– Have the pad as high up your shins as possible to minimise the forces at your knees.
– Keep your hips and knees in line and make sure there is no rotation at your lower leg.
– Ensure the machine doesn’t take you into more knee flexion than you have available. Measure this by sitting on the machine without any weight and seeing how far you can actively bend your knees.
– Hold your pelvis and trunk very still whilst you perform the exercise.
– Use the handles to brace yourself.

Leg curl machine

Remember the study earlier that looked at muscle activation patterns in cyclists with PFPS? The leg curl machine will help you balance the strength in your hamstrings. Just be sure to follow these guidelines:

– Make sure your knees are in line with the axis of the machine.
– Have the input arm pad set just below your calves, and the restraint pad flush with your thighs.
– Keep your hips and knees in line and make sure there is no rotation of your lower leg during the exercise.
– Make sure the machine doesn’t take you into more knee extension than you have available. Measure this by sitting in the seat without any weight and seeing how far you can straighten your legs with the restraint pad on your thighs. Don’t let the machine take you past that point.
– Sit tall on the machine and make sure you stay that way throughout.
– Use the handles to brace yourself.

Hip abduction machine

If adduction of the femur is contributing to your knee pain then it makes sense to strengthen the muscles that oppose that motion — the hip abductors. The hip abduction machine will help you accomplish this. Just make sure you follow these instructions:

– Ensure your backside stays in the seat throughout.
– Have your knees bent to around 90 degrees.
– As you push out, take note how far your legs go to each side. This will give you an indication whether you are weaker on your injured side.
– Return to the starting position but don’t allow the weight to make contact with the stack.
– Slowly push out again.

Calf raises

If a cyclist with PFPS regularly demonstrates a more dorsiflexed ankle position during the pedal stroke (heel lowered, toes raised), it’s possible that weakness in the ankle plantarflexors (the calves) may be playing a role. Calf raises performed on the leg press machine will be effective in improving that. Here are some guidelines to follow:

– Don’t let the machine take your ankles into passive dorsiflexion. Measure this first by standing up straight and lifting the front of each foot off the floor as high as it will go without leaning back. Ensure the machine doesn’t force your ankles back past this point during the exercise.
– Place your feet on the bottom of the leg press platform with your heels slightly over the edge.
– Maintaining a small bend in your knees, push the platform away from you and aim to get the arches of your feet as high as possible.
– Slowly return your heels towards the platform making sure you don’t let your heels drop too far.

Summary

Not being able to get out on your bike because of injury can be very frustrating. This can be a good time for reflection and gaining a better understanding of your body, however. It’s also an opportunity to do things differently and set the foundations for better performance and an injury-free future.

Incorporating resistance training into your programme will not only help you recover from your knee issue, it will make you a stronger cyclist.

Footnotes

1. Medial rotation is a rotation towards the midline and is also known as internal rotation. Lateral rotation is a rotational movement away from the midline.

About the author

Paul Argent is a former Category 1 road racing cyclist from the UK. He now runs an injury rehabilitation and sports performance business in the City of London, Human Movement, which specialises in helping chronically injured athletes and weekend warriors alike get back to doing the things they love better than ever.

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