Patella and pain

My dear friend and cycling partner recently met with a statistical inevitability which left her with a smashed kneecap. As all her riding and racing comrades have fallen in one way or another around her, for years, Jo has been supernaturally lucky where crashes are concerned. Last week, sadly, Jo got knocked down under a set of traffic lights by an oncoming car turning right. The driver simply didn’t see her. After so many thousands of miles, we have to accept that this accident is just probability at work.

Although unlucky getting hit by this car, she was very lucky that her head and axial self remain in the clear and the trauma was confined to three carpal bones and one patella. Jo got kneecapped. Her patella was smashed into many pieces during impact with the tarmac and the surgeon caged them together during surgery. Now the period of healing begins, starting with the immobilisation required at ground zero of her op and Jo is resting comfortably at home now seven days since the accident.

So with my incredibly fit friend now immobilised by this injury, I’m thinking about the patella a lot these days. What is so important about this comparatively tiny bone? Our weight bearing needs nothing of it, but once smashed we are rendered immobile as it heals, and even after the bone itself is healed, the prognosis is sketchy for an athlete like Jo who is interested in more than just walking.

It isn’t just the smashed kneecap that causes pain, as I have learned; the patellofemoral joint can be a troublesome character for cyclists even without trauma. Today I’m going to focus on pain arising from disruption to the gliding patella, why it can be a problem for cyclists, and how you can use Yoga to address the causes. For more on how to integrate yoga into your cycling, check this out.

First we’ll have a quick look at the relevant anatomy of the knee, essentially a diarthroidial hinge joint between the femur and the tibia. Situated on the anterior surface of the encapsulated knee joint, the patella articulates with the femur as a triangular bone composed of mostly dense cancellous tissue developed within the tendon of the rectus femoris muscle fibres.

Together with the other quadriceps muscles, the rectus femoris extends the knee joint as well as functioning as a flexor of the hip. For more about how the recfem impedes backbending, why that’s bad, and how to correct it, see my post regarding Lunge for Life.

Although small on the scale of bones generally, the patella is the largest of the sesamoid bones (bones contained within tendons), and the rest of this discussion will be reserved to its role as a lever for the quads to impose more force for the knee in extension, what can go wrong during this process, and how cyclists can use Yoga techniques to get their glide back.

Sesamoid bones are named for their shape — “sesamoid” is Latin for sesame-shaped. Situated inside the tendons of strong muscles, sesamoid bones  increase the force of these muscles on their affected joint by pulling the tendon further away from the joint’s axis of motion. Just as the handle on a door is always situated on the opposite side of the hinges, the sesamoid bone creates the same distancing affect as it lengthens the lever arm and reduces the force required to “open the door.” Increasing the leverage applied to opening the door, or extending the knee, the patella can increase the force output through the knee by up to 15%.

Jo’s surgeon said that she is likely to experience retropatellar pain, or pain behind the kneecap, as a result of the pulverised patella’s many newly sharpened edges potentially interfering with the articular surfaces. Jo’s injury is due to obvious impact, and we can categorise that amongst other traumas to the knee which produce easily differentiated diagnoses such as ligament and cartilage damage from forceful twisting or pivot trauma.

Because cyclists don’t pivot or twist, they are not vulnerable to the forces required to traumatise the knee internally unless, as in Jo’s case, such injuries are sustained during crash impact or cross-training. So if you’re a cyclist with mysterious knee pain and you haven’t crashed recently, you’re probably dealing with a repetitive strain/biomechanical issues surrounding the PFJ (patellofemoral joint). Whatever the cause, it is beneficial to understand the forces at work, especially when these forces arise not from an extrinsic source, but from our own movement habits. That’s where the Yoga comes in.

During movement, the patella follows a serpentine path as it glides up and down on the femoral condyle. Because the patella needs to slide freely along the articular surface as it does its work, any disruption to the railbed can result in pain and irritation. The perfect pedal stroke is an interesting concept as it removes all the variables of rotation as well as ab/adduction at the hip. This reduces knee movement down to the basics of repeated extension and flexion in the sagittal plane.

Thus the spotlight falls on the PFJ. The patella can just marginally veer off course as a result of the tiniest imbalance in muscle integrity, a leg length discrepancy, weakened core muscles, overtightness, or any other variable in the kinetic chain. In Jo’s case the PFJ railbed might be disrupted with “gravel” but in your case the pain could stem from a microdetail of position on the bike, new equipment, a loose cleat, changes in shoes, or a sudden increase in training volume/intensity. Problems arise when even subtle abnormalities in movement patterns are repeated in high numbers with or without high load.

As pointed out by one of my favourite resources, Coach Rob at Tailwind Coaching, a 4 hour ride conducted with an average cadence of 85 RPM will produce 20,400 pedal strokes. Now we have another set of variables each with their own variables coming into play 20,000+ times over the course of 4 hours. Probability issues encompass questions such as: what are you doing with your feet? How likely are you to stretch after said bike ride? Have you had adequate rest since your last training session; conversely, are you prepared for 4 hours on hilly terrain? Is your lower back compensating for a weak set of core muscles, throwing off your pelvic stabilisation and thus affecting forces at work in the knee?

Add the bicycle-related factors of crank length, saddle height, which affect variables of extension torque of the knee joint against joint angle. We know the knee often articulates over a range between 65° and 150° so as cyclists we can be assured we are using our knees to their best advantage– but only if we’re in the perfect position on the bike will we be able to produce maximum power and avoid injury. Thanks to Bike Dynamics for their great explanation of position variables.

Taking all of the above into account there are many factors that can affect the PFJ and if you’re not on a structured, consistent training program then it is easy to see why knee pain can develop especially in someone with a high cycling load. For diagnosis and treatment, enquire with a sports doctor at MHFS. To prevent and ease the pain long term, consult the Avid Yogi Cyclist Pain Management Plan.

Patellofemoral pain is a diagnosis of altered biomechanics. Much like the vast number of variations in position on a bike, lower limb movement is a complex but fluid combination of movements. When one or multiple parts of this chain of movement is out of line the forces that can be applied abnormally through lower limb structures increases leading to dysfunction and pain. Abnormal patellar movement is one manifestation of altered biomechanics.

There are multiple potential causes for patellofemoral pain which may exist in isolation or, more commonly, overlap. The good news is that with thorough assessment of your injury history and sporting activity alongside clinical examination a management plan can be put in place to help resolve your knee pain. By doing this you have the added advantage of maximising your biomechanics and take one step further towards improving performance in your sport.

In the meantime, most athletes will benefit from a program of focused breathing under stretch in variations of the lunge posture. This topic begins a deviation toward my recent obsession with rectus femoris, so I’ll stay patella-focused and finish this post with a video of simple advice for easing knees that are tight due to the hypertrophic quads we cyclists tend to suffer:

 

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