Proximal Muscle Strength and Foot Injury

The foot is one of the most unstable structures of the human body with 26 bones, 33 joints and the expectation to carry an entire body of weight, there’s a lot of pressure placed on our main form of transport. In this blog we take a look at the structures further up the chain and how they influence the stresses placed on the foot and eventually lead to injury if not properly addressed.

In today’s social media, computer generated and screen dominated society human movement patterns are changing, we are seated more than we once were, children are coddled into activities less kinetic in nature and even that which was once taught amongst physical education in the primary years of learning has been replaced with decreasingly structured and meaningless purpose – all leading to a muscle imbalance, poor muscle activation, poor body control and an atrophy of the most very basic of physical attributes STRENGTH.

Let’s begin our investigation by looking upon the body’s power generators, the muscles which are now so poorly utilized for the purpose of active movement and over requested to be a glorified cushion for the day to day adventures of work and unfortunately entertainment – The Glutes.

The posterior muscles of the hip joint commonly grouped together as “The Glutes” after the three larger and more superficial prime movers, are responsible for extension of the hip as well as both lateral and medial rotation of the femur. As touched on earlier, the average person in society today has a decreased sub-conscious ability to activate these muscles when required. Quite regularly the hamstrings are used as the primary muscle group for hip extension and the Quadratus Lomborum of the lower back as the primary core stabilizer, which although both important in these actions should in fact be secondary to the glute region when comparing size and position relative to the joints they are acting upon.
A decrease in neuromuscular connection, activation ability or comparative strength to the opposing muscle within the gluteal region may lead to conditions being prominent within an athlete or patient associated with internal lower limb rotation, external rotation of the lower limb and quadriceps region dominance, detailed in the table below. At this stage it is important to outline that a singular deficit in a particular muscle group is less likely to cause a pathological movement or complaint, however will be one of a number of both subjective and objective findings which will contribute to the issue.

Glute Region
Muscles	Action	Deficit Issue	Pathological Condition
Piriformis	Lateral rotation of the Femur. Abduction of the Femur. Extension at the hip joint.	-Internal rotation of the lower limb. -Hamstring Extension. -Quad Dominance.	In-toeing ITB Syndrome Hamstring Overuse Medial Knee Pain Sciatica Medial Tibial Stress Syndrome Anterior Tibia Stress Syndrome
Obturator Internus
Gemellus Superior
Gemellus Inferior
Gluteus Maximus
Gluteus Medius	Abduct the Femur. Stabilizes Pelvis. Internally rotates femur.	-Internal rotation of the lower limb. -Pelvic Instability- Externally rotates femur	Tibialis Posterior Injury Increase Pronation Navicular Stress Achilles Tendon Injury
Gluteus Minimus
Tensor Fasciae Latae	Stabilize Knee in Extension	-Decrease Knee Stability	Medial/Lateral/Posterior/Anterior knee pain

Quite regularly when the muscles of the glute region are compromised it leads to the muscles of the anterior thigh to become dominant. The primary movements of the anterior thigh muscles are to flex at the hip, bringing the torso forward and placing further weight over the top of the foot; and extension of the knee, which when further utilized over the posterior thigh muscles leads to a locking of the stable joint and increasing the risk of injury as momentum carries over the structure and the body is forced to find the necessary movement at other joints.
However, if the anterior thigh muscles are underutilized it can also lead to conditions in the lower limb. This is not commonly recognized in populations with nil underlying health conditions but can be associated with those who use the posterior thigh muscles when compensating for lack of glute strength. A muscle imbalance around the thigh region once again leads to a pathological rotation of the lower limb which places untoward stress on the associated structures. The Illiotibial Band, a connective tissue overlying the lateral thigh is one of the structures which can become inflamed or injured with excessive rotation. Additionally, the anatomy distal to the knee can become at risk due rotation acting upon the tibia and further down the chain at the foot increasing pronatory forces. Compromise of the muscles in the glute and posterior thigh region can also increase the amount of muscle spasm and irritation at sciatic nerve leading to a loss of proprioception, nerve pain and further innovation loss.

Anterior Thigh
Muscles	Action	Deficit Issue	Pathological Condition
Psoas Major	Flexes the Thigh at the hip	-Increase Hamstring utilization -Increased pronation -Poor VMO activation	Anterior Knee Pain Medial Knee Pain Gastrocnemius Injury Popliteus  Injury ITB Syndrome Medial Tibial Stress Syndrome Anterior Tibia Stress Syndrome
Illiacus	Flexes the Thigh at the hip
Satorius	Flexes the thigh at the hip. Flexes lower leg at the knee
Rectus Femoris	Flexes the thigh at the hip. Extends Lower leg at the knee
Vastus Medialis	Extends the Low Leg at the knee joint
Vastus Intermedius
Vastus Lateralis

Posterior Thigh
Muscles	Action	Deficit Issue	Pathological Condition
Bicep Femoris	Flexes leg at knee joint. Extends and Externally rotates thigh. Externally rotates leg at knee	-Increased Quad utilization. – Gastrocnemius Overuse -Internal rotation	Internal rotation of the lower limb Medial knee pain ITB Syndrome Sciatica Hamstring Injury
Semitendinosis	Flexes leg at knee joint. Extends and Externally rotates thigh.
Semimembranosis	Flexes leg at knee joint. Externally rotates thigh. Medially rotates leg at knee
Gracilis	Adducts and flexes thigh at hip joint.	-Abduction at thigh	Lower Limb Abduction Increased pronation Tib Post Injury
Pectineus	Adducts and flexes thigh at hip joint.
Adductor Brevis	Adducts thigh at hip joint.
Adductor Magnus	Adducts thigh at hip joint. Medial rotates thigh	-External rotation at the hip	Lower Limb Abduction Increased pronation Tib Post Injury
Adductor Longus	Adducts thigh at hip joint. Medial rotates thigh
Obturator Externus	Laterally rotates the thigh

The extrinsic muscles of the foot, those which begin in the lower leg and cross the ankle joint into the skeletal structure of the foot are those most attributed to the cause of foot pain of all the proximal muscles. Both the posterior and anterior leg muscles are responsible for the actions which take place upon the medial and transverse axis of the foot.
The posterior leg muscles, referred to in laymen terms as the calf muscles are responsible for the plantar flexion of the foot and at times flexion of the knee. A lack of strength and flexibility in the posterior leg muscles can lead to poor propulsion due to a decrease in dorsiflexion at the ankle joint. Additionally, overuse injuries are quite frequent within this muscle group as these smaller muscles are called on to be a person’s primary mode of transport in day to day life. Tibialis Posterior weakness is a common observation seen within the excessive pronation population; this muscle is responsible for inverting the foot as well as slowing the pronatory forces which are occurring at foot at any given time. If the muscle does not maintain the strength to support the medial longitudinal arch or resist the pronatory movement further pathological implications can occur.
The anterior muscles of the lower leg, which are often described by patients as “the shin”, grouping it with the laymen term for the tibia bone, fall laterally to the bone itself. These muscles are responsible for the action of dorsiflexion and eversion at the foot as well as extension of the toes. An inability to dorsiflex appropriately for ground clearance during gait can lead to falls within both the young and older populations. While ankle equines in children is usually seen to be a bony block or calve tightness associated with over activity and is easily addressed; in the older population the strength of the muscle to perform the task at hand is found to be in a deficit, this at times can in fact be life threatening.
Similarly, if the anterior toe extensors are too active and causing a retraction of the toes the risk of falls is once again increased. Toe retraction can be linked to inter-digital neuritis, compressing the nerves which innovate the small muscles of the foot and reducing proprioception to the area.

Posterior Leg
Muscles	Actions	Deficit Issue	Pathological Condition
Gastrocnemium	Plantarflexes foot and flexes knee	-Poor Landing Mechanics -Poor Propulsion – Excessive Supination	Dorsiflexion Equinus Achilles Tendon Injury Bursiitis Severs Posterior Compartment Syndrome Tib Post Tendon Injury or Dysfunction Nerve Entrapment Lateral Loading of the foot
Plantaris	Plantarflexes foot and flexes knee
Soleus	Plantarflexes foot and flexes knee
Tibialis Posterior	Plantarflexes  and inverts foot. Supports MLA
Popliteus	Stabilizes the knee	-Excessive Lateral rotation at knee	Lateral Ligament Damage ITB Syndrome Popliteus Injury
Flexor Hallucis Longus	Flexes 1st Toe	-Poor Proprioception – Poor Propulsion – Poor Balance	Apropulsive gait Balance issues
Flexor Digitorum Longus	Flexes Less Digits

Anterior Leg
Muscles	Actions	Deficit Issues	Pathological Condition
Tibialis Anterior	Dorsiflexion and Inversion	Equinus Increased pronation	Poor Foot Clearance Lateral Foot Pain Rapid Pronation Peroneal Tendon Injury 5th Metatarsal Injury Anterior Compartment Syndrome inter-Digital Neuritis Sesamoid Pain Medial Tibial Stress Syndrome Anterior Tibia Stress Syndrome
Fibularis Teritus	Dorsiflexion and Eversion	Increased lateral Loading Foot Clearance
Peroneus Longus	Plantarflexion and Eversion
Peroneus Brevis	Plantarflexion and Eversion
Extensor Longus	Dorsiflexion and Extension of 1st Toe	Digit Retraction
Extensor Digitorum	Dorsiflexion and Extension of lesser toes

In conclusion, it has been well established that the feet can affect muscles, joints and other structures further up the chain of command, if a joint is unable to produced the required range of motion for a particular action, it will look for it at other body areas, whether this is optimal for performance or not. Similarly, if the larger structures of the body which are situated close to the Centre of Mass do not have the strength to support, control or activate purposely; then the structures placed distally to the body will receive untoward force and in turn may result in overuse injury or acute damage.

During the month of March we look at Cycling and how as a podiatrist we can make adjustments to the feet as well as the proximal structures to help develop the best possible ride for an athlete who is producing open chain movements in a closed chain situation.

Jackson McCosker
Director /Chief Editor

References

Brukner, P., & Khan, K. (2007). Clinical Sports Medicine. Mcgraw- Hill Education Pty Ltd.
Dugan, S. A., & Krishna P. Bhat. (2005). Biomechanics And Analysis Of Running Gait. Physical Medicine And Rehabilitation Of North America , 603–621
Michaud, T. (2011). Human Locomotion: The Conservative Management of Gait Related Disorders. Washington: Newton Biomechanic.

MILNER, C. E., FERBER, R., POLLARD, C. D., HAMILL, J., & DAVIS, I. S. (2006). Biomechanical Factors Associated with Tibial Stress Fracture in Female Runners. Applied Sciences , 323 – 328.