Runner’s knee syndrome is very common among amateurs and athletes who practice running. We analyse the main causes.
What is it
Runner’s knee is the colloquial name of femoropatelar syndrome, a change in the structure of the knee which leads to the degeneration of the joint cartilage and produces intense pain from the friction between the patella and the femur in the joint flexo-extension.
How it manifests itself
The knee is a complex synovial joint structure (diarthrosis) that has great mobility.
Figure I. Osteo Articular structure of the knee.
This is the main cause why it is a joint that causes us many problems.
As humans, we walk in bipedation, so the lower limbs are in continuous movement and tension, receiving impacts systematically. The knee joins the femur with the tibia and fibula, and as a connection of both segments, take on a great burden in daily activities (walking, climbing stairs, exercising…)
Who suffers from it?
However, there is an increased risk of developing this condition in a population group: athletes.
People who exercise, especially those who exercise with high intensity, duration and/or frequency, have accelerated joint metabolism and a much greater risk of developing premature osteoarthritis (Van Dijk et al., 2016; Amoako et al., 2014; Vannini et al., 2016).
Sport as a cause of runner’s knee
This is a widely misused concept, and is that there are direct mechanisms through which we can associate the practice of physical exercise of impact (such as running) with bone and joint degeneration, and therefore with the development of joint disorders, pain and injuries.
However, the relationship is not so simple, and all the causes of developing an injury must be evaluated.
Runner’s knee is a syndrome that occurs when continued overuse degrades articular cartilage (sometimes pain occurs before this process begins), causing exposure of the bone by degeneration of the protective structures and damaging the bone marrow by rubbing the kneecap with the femur.
Figure II. Grades I-IV of cartilaginous damage to the knee joint.
This figure shows the runner’s knee with a structural alteration, classic in middle-advanced athletes, and even in non-athletes, many elderly may suffer this simply from joint degradation over time (Petersen et al., 2014).
However, not whenever there is discomfort and pain there is a structural alteration of the joint, that is, there does not have to be a degradation of the cartilage and damage to the bone to suffer runner’s knee (Van Der Heijden et al., 2016).
Patellofemoral pain syndrome
This is what happens to young people with this condition, and this is called patellofemoral pain syndrome.
Figure III. Chart Flow of the development of patellofemoral pain.
It is important to detect it and to know how to act before it causes structural damage to the joint, which is a problem because 25% of athletes diagnosed with this syndrome stop exercising.
Tendonitis on the knee
In general, the main causes attributed to the appearance of the runner’s knee are structural changes:
- Damage to the joint-bone assembly.
- Tendonitis and insertional tendinosis.
- Patellar instability.
The real cause
The real cause of runner’s knee appearance is an excess training load to which the tissue is not adapted; which usually leads to poor biomechanical adaptations to the physical exercise being carried out, and which produce structural alterations that worsen with the excess load.
Basically, a vicious circle.
Where is the problem?
The main manifestation of the problem is the knee, is the patellar deviation:
This deviation is observed when we perform physical exercise, for example, in the so-called functional dynamic value, where the femur or tibia (or both) rotate internally and cause the knee to move “inward” (adduction);
A position in which you should not find yourself in, and which dramatically increases friction resistance, degenerating cartilage.
Figure IV. Graphical representation of a functional knee valgus.
The knee joint, that undergoes this position for a long time (e.g. in athletes), ends up displacing the patella outward, hindering muscle control over the joint and producing a greater instability on the knee that increases the risk of acute injury (such as a subluxation or dislocation), and/or chronic (tendinitis, cartilage degradation, osteoarthritis).
This condition is called patellar deviation.
Figure V. Graphical representation of the patellar displacement in front view (A) and axial (B).
Poor foot position during motion can cause a knee disturbance.
The main reported cause through which the feet can lead to developing runner’s knee is the eversion of the back of the foot (pronation of the sole of the foot) that causes the tibia to rotate internally, and with it the knee is “turned inside” (i.e. approaches the longitudinal axis of the body) (Mo et al., 2013; Morley et al., 2010).
Figure VI. Graphical representation of eversion in the stride.
The weakness in the muscles that externally rotates the femur, or that abducts the hip, is key to the development of the corridor knee syndrome.
People who develop the runner’s knee have marked weakness in these muscles.
Strengthening the pelcubantereal musculature is key to preventing this condition and possibly the most important factor we can control as sports people.
A big weakness in the quadriceps (Crossley et al., 2016) as well as an isquiosural dominance (White et al., 2009) are risk factors in the development of runner’s knee syndrome.
However, sometimes detection is not so simple, as balances in the production of strength of the different muscles that form the quadriceps can also alter the patella and produce the effect of patellar deviation.
Figure VII. Graphical representation of the different degrees of the Q angle and their consequences on knee displacement.
It is called the Q angle, the angle that is formed by the line of the Superior Iliac spine line with the center part of the patella, and the line of the center part of the kneecap to the tuberosity of the tibia; and determines the force vector of the quadriceps (seen lighter in the following image).
Figure VIII. Graphical representation of angle Q. Fq is the force vector of the quadriceps, Fp is the vector of patellar force, and Rl is the net result of the forces.
Normally people with runner’s knee syndrome have strong external vast quadriceps (the front of the outside of the thigh) and a weak internal vast (the opposite).
Figure IX. Myology of the thigh.
This is a minor cause, but it has been observed that those with runner knee syndrome have a lower inclination of the sacrum that is the welded bone found under our spine.
Figure X. 3 types of pelvis depending on the degree of sacral inclination.
Symptoms of Runner’s knee
The most obvious, and only symptom you should worry about with runner’s knee, is the pain.
Since it is the one that appears first and since if there is no pain or difficulty in carrying out your daily activities you should not worry about any type of structural change.
“I have one leg shorter than the other” It doesn’t hurt? Don’t touch it.
How to treat Runner’s knee
There are many treatments to improve Runner’s knee; among them:
Pad or brace for Runner’s Knee
The knee brace is a fabric structure that is located inside the orthotic tools for the joint support.
This accessory helps to center the displacement of the patella, preventing the quadriceps force vector from moving the patella.
Draper et al., (2009) demonstrated that the use of knee pads was effective for the treatment (short-term) of runner’s knee syndrome, increasing the contact surface of the kneecap with the femur and decreasing its displacement.
Figure XI. Knee brace effects on the placement angle of the kneecap.
Exercises for Runner’s knee
Physical Exercise is the main physiotherapeutic treatment for the runner’s knee.
It is important to be able to assess what are the specific causes in your case in order to be able to treat it correctly.
Figure XII. Execution model of a hip abduction exercise.
It might also be helpful to make sure your quadriceps are strong and not dominated by the strength of your isquiosurales.
Similarly you should make sure that there is no imbalance in the strength of the different muscles that make up your quadriceps.
For that, it’s best to do a pistol squat as a test and record it from a frontal view.
Figure XIII. Different A-D graduated models depending on the dysfunctionality shown in an eccentric unilateral squat test for diagnosing the cause of runner’s knee.
- If your movements look like A, good work;
- It if looks like B, you should strengthen your core, you are unstable, friend…;
- If it looks like C your hips are failing, you have weakness in the pelvic muscles, and you should work them as I indicated above;
- And if it looks like D… you are quite bad, as you show a loss of control over the knee, hip and eversion of the foot.
Surgical treatment of Runner’s Knee
Surgery is the last option for the treatment of patellofemoral pain.
It should only be applied in very specific cases, such as grades III and IV of osteoarthritis, so in young people it is completely discouraged to operate unless a specialist recommends it and establishes it as the most recommended guideline for treatment.
Supplements in the management of runner’s knee syndrome
There are food supplements that we can use to deal with runner knee syndrome, especially the discomfort it generates.
First glucosamine, an aminoglycan that has been shown to be effective in preventing cartilage wear in athletes (Yoshimura et al., 2009).
MSM is a sulfur compound that has been a characteristic of joint pain caused by knee osteoarthritis(Debbi et al., 2011)
The combination of glucosamine and MSM has been shown to be more effective than both compounds separately in the adjuvant treatment of osteoarthritis, so they act in synergy(Usha y Naidu, 2004)
Did you know you have this combination in our Joint Care?
Finally, ginger root extract is a great nutritional supplement to attenuate the inflammatory response thanks to its high content in ginsenosides that act as antioxidant and anti-inflammatory alkaloids(Mazidi et al., 2016).
High intensity, duration, and impact physical exercise, with poor load management is a determining factor in the development of the runner’s knee.
Once the pain appears you should control it with rest, cold, compression, and elevation of the joint.
You should retrain as soon as possible, in a controlled manner so that you don’t lose the functionality of the joint.
Training with control is not a problem!
It’s going to help you, so you don’t have to quit sports. Strengthen your muscles External rotators and hip abductors, and your quadriceps.
Use anti-inflammatory and chondroprotective supplements during the recovery process to be ready as soon as possible!
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- Sports Supplements Guide for Runners
- Supplements for the Joints