Systemic biomechanical issues
Table of Contents
Review / To the top
Here is what we learned in the previous section. These points will be the key to elucidating how movement dysfunction develops.
Shoes tend to cause the problems of
- Tight calves resulting in loss of 10-20 degrees of dorsi-flexion ROM in the calves.
- Inactivation of the muscles on the bottom of the foot and the ankle stabilizers
- Decreased proprioception of the lower limb
Sitting tends to cause the problems of
- Inactivation of the gluteal muscles.
- Tight hip flexors (iliopsoas, rectus femoris, sartorius, tensor fasciae latae [TFL], and adductors longus and brevis).
There are two different ways the body will compensate because of these problems. The first is having the shins angle inwards towards the midline; this is called valgus stress and in extreme cases can be seen as a valgus deformity shown below. The second is having the shins angle outwards away from the midline; this is called varus stress and, similarly, in extreme cases can be seen as a varus deformity which is the opposite of the picture below. In regards to sitting and shoes, valgus stress tends to be more common for multiple reasons, so I will be discussing that most of the time. I will only talk about varus stress briefly. Those that are interested in further reading may contact me later.
Photo from sagepub
Please note again I am only describing the most common way these movement disorders develop. You or someone you know may only have one or a few of the symptoms. Some people have all of them and tend to develop injuries much faster than others. Each case is specific to the individual.
Valgus stress / To the top
Valgus stress is more common because it is a compensation from multiple aspects of shoes and sitting that we have described before. The body naturally compensates when it cannot perform its abilities. For example, if you smash your leg against a corner you naturally compensate with a limp to avoid putting pressure on the injured limb until the pain subsides. Similarly, if your shoulder is hurting you will naturally compensate by side bending in your spine to get your arm overhead.
It is common for the body to naturally compensate with valgus stress because of shoes and sitting. The first “symptom” that usually appears for most people is inward tracking knees. This occurs for multiple reasons.
- First, the loss in 10-20 degrees of ROM from the calves must go somewhere. The next joint above the ankle where the ROM is lost is the knee. Thus, instead of the knee tracking directly over the toe, the lost ROM is compensated by the knee tracking inwards.
- The glutes, especially gluteus maximus and medius, are potent external rotators of the femur. Since the glutes are inactivated with sitting, the femur is allowed to rotate internally in knee bending. This allows the knees to track inwards.
- Adductor longus and brevis are tight and shorter from sitting. The gluteal muscles are also abductors of the femur. Since the glutes are inactivated from sitting, the adductors will tend to pull the knee medially as it bends (eccentric movement).
- Adductor magnus is involved in hip extension. Since the glutes which are primary hip extensors are inactive, a strong OR weak adductor magnus will tend to pull the knee medially as it straightens (concentric movement).
Note: The adductor issues are two separate issues and should not be grouped together. The biomechanical issues with both will have some differences when we discuss how to correct the issues later.
Note 2: It seems there is some confusion on the theory of weak adductors and valgus (Starting Strength pg 46-49). The weakness in adductors is specifically for adductor magnus which let’s the knees cave in during the concentric. As I said, this is a separate issue from the knees caving in on the eccentric.
What happens with a weak adductor magnus is that coming up from the bottom of the squat the hip extensors are at their longest position. Muscles are normally strongest at the middle of their range of motion shown on the force-length curve. This means that the knees cave in to shorten the magnus towards the middle of its range of motion where it is the stronger. If the glutes and abductors were active and stronger this would not happen; however, since they are more inactivated, the adductor magnus along with the hamstrings become primary hip extensors thus pulling the femur medially.
Why is the lost ROM in the calves such a big issue? Well, this study in tennis players shows that restricting ROM in the ankle “may also provoke large internal forces elsewhere.” Stiff shoes were found to the be the worst, and ones that moved better were superior. Obviously, the natural foot itself would be the most flexible in regard, but unfortunately cannot be used by itself extensively on extremely rough surfaces.
Inward tracking knees tends to precipitate a cascade of other postural and biomechanical dysfunctions which affect the other muscles, connective tissue, and eventually the joints within the legs.
Muscle and connective tissue issues
- Flat feet / pes planus / collapsed arches – Internal rotation torque and medial tibial tilt at the talus put most of the weight distribution on the medial arch of the foot. Combine this with inactivated muscles on the plantar foot from the shoes, and the arch collapses. The picture shown below compares a foot with a correct arch (top) to that of a fallen arch (bottom)
Photo from michaeljtodd
You can test this by standing up and allowing the knee to track in. You will see and feel that the tibial torsion at the talus pronates the foot and allows the majority of the weight to rest over the medial arch of the foot.
Likewise, this analysis of increased forefoot loading (from higher heel shoes) leads to greater medial stress on the foot as well.
This study showed that there is greater stiffness in the forefoot especially during barefoot running compared to running with shoes. This is good in the respect that the plantar aspect muscles are firing to maintain the arch. A lack of stiffness in the foot indicates that the muscles are not firing effectively and thus a greater flattening of the arch is occurring in strides. Repetitive stress like this may lead to collapsed arches.
- Plantar fasciitis – Like flat feet the inactive muscles on the foot allow the arch to collapse some putting stress on the plantar fascia. Tight calves contribute as the fascia from the plantar foot is continuous up the posterior chain and pulls on the calcaneus.
It is likely that you only develop either flat feet or plantar fasciitis. Although it is possible to develop both. If your plantar fascia is more lax and stretches easier, it is easier to have the arch collapse all the way even before plantar fasciitis may develop. When the intrinsic muscles of the foot are inactive, the plantar fascia is the last stopgap that holds the medial arch together before it collapses. Since the connective tissue is not built to take that kind of stress, it gets inflammed and painful.
Extremely tight calves, and extended time with heel elevated shoes may lead to this condition solely. A lot of it is variable depending on the person. Remember, I am just describing some of the cases.
- Achilles tendonitis and rupture – the internal rotation torque and medial tilt of the tibia at the talotibial joint in combination with plantar flexion in movement increases the likelyhood of damaging the achilles. All tendons and ligaments work best when pulled on directly like a piece of paper, but when you twist a piece of paper and pull it tears more easily.
Photo from jaapa
In respect with past runners the incidence of achilles injuries has decreased. This is because the calves were involved more when footwear was minimal. But now, with decreased ROM in the calves, the injuries tend to migrate elsewhere. We will see this in the following points.
The torque at the ankle and thus achilles tendon especially in movements on the toes makes this injury appear more frequently than it should. This is in combination with very tight calves.
- ACL sprains and tears – like the achilles the inward tracking knee tends to torque the ACL. Thus, spraining and tearing the ACL is more likely.
Note the inward tracking does also stress the MCL. But for time purposes I am not including this. Just know that in the event of a torn ACL with twisting there is often accompanying MCL sprain or tearing as well. In severely traumatic injuries the unhappy triad (ACL + MCL + meniscus tear) often occurs.
Photo from doctorkolstad
At this point we need to note that women have increased incidence of ACL injury especially because of Q-angle. Womens’ hips are wider for child birthing and thus their knees have to travel further in at an angle under them to support their weight. This greater angle obviously leads to increased torque on the connective tissues at the knee.
This analysis demonstrated that valgus knee angle puts more stress on the ACL as their experiment showed that women land more often in knee valgus position. However, they found no different in gluteus medius activation between the sexes. I do not find the difference in gluteus medius activation troubling since both men and women are both sitting for 7-8+ hours a day in the classroom and doing homework. It would be an interesting comparison if they compared athletically dominant men and women versus the rest of the population though.
- Quadriceps dominance and tightness – the body senses the stress on the ACL from its proprioceptors. If the knees cave in too much obviously it is going to stretch out the ligaments or tear them. To stop this it strongly strengthens the quadriceps, especially the lateral aspect of the quad.
Women as well as men both develop this problem because everyone has a Q-angle. In addition, because the glutes are inactivated, the decreased force output of the hip extensors is compensated by the quads which are the knee extensors. This is also why women tend to be less athletically inclined than men, and also why quad dominant men are not-so-good athletically. For example, this study shows higher vastus lateralis development, higher quad to hamstring strength ratio, and lower gluteal activation in women because of Q-angle and valgus knee stress. This quad dominance in women is indicative of a higher risk of ACL injury than men. Similar results were obtained in this study examining Q:H imbalance in both the medial and lateral aspects of both the quads and hamstrings.
This study showed that increasing heel height (especially with high heels) increases quadriceps activation. There were no intensity increases but with muted glute function we do not need increases in repetitive intensity to see quadriceps dominance to develop. After all what we practice we get better at. If we practice “activating” the quads, we will develop quad dominance. This will also be a key later in redeveloping gluteal activation and strength.
Quad dominance does not only have to do with ACL injuries. Increased quad eccentric loading has been shown to be implicated in the development of patellar tendonopathy/tendonitis.
- Tensor fasciae latae (TFL) and iliotibial band (IT Band) strength and tightness – since the glutes (especially gluteus medius) are weak, the TFL compensates for the body to maintain proper abduction abilities. In addition, increased stress is placed on the TFL and IT band when the knees cave in which strengthens these structures.
Photo from realbodywork
TFL and IT Band tightness, in combination with lateral aspect quad dominance often lead to patellofemoral syndrome where the patella starts tracking off to the lateral side of the knee. In addition, this may cause chondromalacia patellae which is wearing down the articular cartilage on the underside of the patella causing pain.
Extremely tight TFL and IT Band also may cause IT band syndrome as well. In IT band syndrome, the IT band and TFL get extremely tight and start rubbing against the femur itself or other muscles in the area. This creates pain and inflammation.
Bringing up the strength of the glutes to take forces away from the knee and back properly to the hip, like this one case study with gluteus maximus and medius strengthening showing improvements in patellofemoral pain. The same is true in this study of iliotibial band syndrome.
There are even cases where a tight IT band and TFL with a weak gluteus medius can contribute to lower back pain.
- Hamstring weakness and tightness – as we have discussed, the quads become extremely strong and tight, this anteriorly translates the tibia with respect to the femur. This also puts stress on the ACL. To protect joint integrity (anterior-posterior) the body will lock down the hamstrings into extreme tightness to protect the ACL from sprain and rupture.
All quad dominant men have extremely tight hamstrings which are often extremely weak. Women, who tend to have less muscle mass overall, also have their hamstrings lock down. However, since there is less mass to protect the joint it also increases the likelihood of ACL rupture.
We’ve been talking about it before but increased Q-angle, quad dominance, and this all contribute to the 3:1 ratio of women:men in ACL tears.
Athletically inclined quad dominant males and females will often have tight strong hamstrings. This is the other alternative, so it does not necessarily mean hamstring weakness is universal. Since the glutes are inactivated, the hamstring takes over the hip extension and will thus be stronger. Tight, strong hamstrings are notoriously difficult to loosen up.
However, tight hamstrings are often prone to hamstring and groin strains/pulls as well. Incidentally, the decreased activation of the glutes increases the propensity of hamstring overloading and strain.
Note: hamstring tightness may also be instigated or exacerbated from sitting in slouched positions for longer periods of time.
- Deep intrinsic butt muscles tightness – as we know the gluteal muscles are inactivated, so the deep intrinsic muscles lock down to protect hip joint integrity.
Normally this is not as important as the other dysfunctions, but some conditions can arise from this such as piriformis syndrome, SI joint, and lower back pain. In some of the population the sciatic nerve runs through the piriformis muscle in the buttocks. Thus, when the piriformis becomes tight and locked down because of gluteal weaknesses you will often see pain in the glute area and often radiating on down into the leg.
Gluteal weakness (2) and problematic activation patterns (2), (3), (4). Similar findings are true with SI joint pain (2). Now what causes gluteal weakness and incorrect activation patterns? Yes, sitting.
Also, as we stated before decreased hip ROM / mobility refers the mobility to another joint. The next joints in line are the SI joint and lower back. The SI joints and lower back are not meant to be mobile. When you increase the range of motion in those joints you often see increased incidence of sharp pain in the SI joint, potential for bulging and herniated discs, and asymptomatic lower back pain.
Joint issues. I put these last because usually it takes months or years within the aforementioned muscle and connective tissue imbalances to develop joint issues. Our bones remodel to the stress we put on them, and bone tissue is turned over every ~3 months or so. If our posture and biomechanics are out of alignment it will stress the bones and will eventually result in deformity.
In the case of valgus stress, most of the joint deformities are listed in this wikipedia article on valgus deformity.
- hallux valgus – or bunions are formed by repetitive inward tracking stress and weight distrbution over the medial arch.
Photo from twoshots.blogg.se
There are actually two cases of how this occurs.
Repetitive stress over the medial arch plus the talar medial tilt will start to collapse the arch. Since all of the bones of the foot are connected, the stress from the collapse must go somewhere. The stress does not deform at the ankle where the bones and ligaments are the stronger. Rather the stress translates out to the farther part of the arch which is at the 1st metatarsal-phalangeal joint. Since the foot is on the ground and has the 2nd metatarsal next to it, hallux valgus forms by pushing the head of the 1st metatarsal outward. This is the place of least resistance (rather than upwards). Thus, most of these types of bunions are associated with collapsing arches / flat feet.
Alternatively, in some cases the inward stress at the knees pushes the ankle into varus (or higher arches). A varus ankle will twist the proximal metatarsals laterally and superiorly. This makes the head of the 1st metatarsal deviate medially and inferiorly. Obviously, since it cannot deviate inferiorly, it only deviates medially forming the bunion.
- Collapsed arches – the intrinsic muscles of the foot are inactive plus more medial weight lead to the collapse.
We already discussed this before, but permanent collapse is possible if allowed to last too long. The bones of the foot will adopt a more permanent planar foot configuration often with bunion formation.
Collapsed arches is one of the other ways valgus stress can be initiated. For example, collapsed arches tilt the talus. This makes the foot pronate. The pronated foot ‘encourages’ the tibia to internally rotated and tilt medially as well. You may see valgus stress appear in people with severely pronated feet even if their upper leg and patella are still oriented forward compared to the foot pointing outward.
- talipes valgus – inward tracking knees and talar medial tilt results in the ankle joint being deformed to the stress.
Photo from dinc
This deformity is usually associated with flat feet as well. When the arch collapses the talus is permanently tilted medially. Thus, the ankle bone is allowed to deform as weight bearing continues.
- genu valgum / knock knees – the medially and internal rotation tilt of the tibia and femur may lead to this.
This deformity is rarer than the ankle ones. It is usually seen in kids, but it can be present in adults if there is too much valgus stress at the knees.
- coxa valga – this deformity is actually not that noticeable by the layperson. Fortunately, it does not really need to be that noticeable because it is mainly only seen in children.
The reason coxa valga is for the most part only seen in children is because there is more weight and thus stress at the lower extremities than at the hips. Thus, it is way more likely to develop a different disorder at the knees, ankle, or feet. This is especially true with adults who have more total weight over their knees, ankles, and feet.
One of the reasons why soccer is the sport with one of the highest incidences of injury is because of extreme amounts of repetitive use combined with improper strength and conditioning. For example, this study on soccer shows that it exacerbates the valgus related stresses because most of the weight is distributed medially in soccer movements.
Valgus stress and pronation has been indicated in weight distribution over a smaller area of the foot. This is an increased weight to surface area ratio which means that it is more likely to develop injuries with the valgus condition compared to the varus. Another reason why valgus injuries are more common.
Also, remember that my descriptions are only one way to develop such injuries. Some people with flat feet just have decreased proprioception from shoes and that is enough to allow their arch to collapse. That then tilts the talus and the knee tracks inward from there. So there are definitely many cases for how different injuries arise.
The one thing we must keep in mind is that the body functions as a unit and usually it goes until it breaks in one area. Thus, we generally only have the propensity for developing one such injury at a time. On the other hand, it is certainly possible to develop multiple injuries depending on the person. In most people I have seen with at least one of the injuries described above, they have at least 2-4 if not more of the symptoms of valgus stress on their lower body. Keep this is mind later when you are analyzing yourself.
Varus Stress / To the top
I am only going to be briefly talking about this because for one it is not very common to have issues relating to this stress deformity.
Now, the other way that the loss of range of motion in the calves is compensated for is with external rotation of the hip. This may result in varus stress especially if the knees come outward. However, this is rare.
External rotation of the hip is most common in the elderly. As we sleep all of our muscles relax. If you sleep on your back (which is how you should sleep), most people allow their legs to relax with the feet pointed out. When you are in this position for 8 hours, much like sitting this allows the external rotators of the hip to become tight and the internal rotators to be stretched out and weak. Thus, hip, knee, foot turned out posture is developed from both sleeping, and loss of range of motion the calves.
The “most” common symptoms are at the feet and ankles again because of increased weight distribution on the lateral aspect of the foot. Fortunately, the associated conditions are high arches and the increased propensity to roll the ankles. This is in comparison to development of hallux equinovarus / club foot which is more common in children with developmental problems.
Suffice to say for most people with high arches or chronic ankle rolling it is important to avoid shoes especially with padding because they encourage this nonsense. We will talk about this later as well.
In conclusion, we learned that the valgus stress of inwards tracking knees is propagated by shoes and sitting because
- The lost ROM from the ankles is gained at the next joint which is the knees.
- Inactivated glutes which are external rotators allow the femur to rotated internally which encourages inwards knee tracking.
- The tight adductor longus and brevis in conjunction with the inactive glutes pull the knee medially in eccentric movement.
- Adductor magnus in conjunction with in inactive glutes pull the knee medially in concentric movement.
These often lead towards the muscle, connective tissue, and joint issues of
- flat feet / collapsed arches / pes planus
- plantar fasciitis
- achilles tendonitis or rupture
- ACL sprain or rupture
- quadriceps dominance and tightness
- tensor fasciae latae dominance and tightness
- iliotibial band tightness
- hamstring tightness (weakness or strength)
- deep butt muscle tightness
- SI joint or lumbar back pain
- hallux valgus / bunions
- talipes valgus
- genu valgum / knock knees
- coxa valga, while possible, is usually a developmental issue
After having reread the Neanderthal No More Part one article, Cressey and Robertson have come to a lot of the same conclusions I did (before me of course). It’s worth a read for their take on the same thing as well.
In the next segment, we will talk about how to evaluate dysfunctions and some corrections you can make.
Did you like this article? Check out these related articles:
- A Firm Foundation: Focusing on the Feet
- Understanding the Foot and Hip’s Role in Knee Pain
- The Dreaded ACL Tear – Rehab Protocols from JOSPT and Solutions for Coaches and Trainers
- So, You Hurt Your Lower Back
- On Tendonitis