We will talk about:
Anatomy of the lower leg (between knee and ankle)
Stress injuries in the lower leg (between knee and ankle)
Diagnosis
Contributing/risk factors
Treatment
Let's get start:
Section 1 Anatomy of the lower leg:
Bone - tibia and fibula
Compartments - anterior (front), lateral (outside), posterior (backside)
Muscles - and their functions
Lower leg bones - tibia and fibula:
Tibia
The tibia, also known as the shin bone, is the 2nd biggest bone in our body behind the femur (thigh bone), bearing our body weight. Its upper part is attached to the femur to form the knee joint, and the lower part attaches to the talus (ankle bone) to form the ankle joint. The tibia is located in the anteromedial (front and inside), closer to the body's central line than the fibula.
Fibula
The slender fibula, also known as calf bone, plays minimal weight-bearing function; it lies posterolateral (back and outside) of the tibia. At the proximal end is the head of fibula attaching to the tibia. The fibula connects to the talus (ankle bone) at the distal end, forming the ankle joint. Fibula serves mainly for muscle attachment and provides stability to the ankle joint.
The tibia and fibula bodies are connected by an interosseous membrane, which is a strong oblique fiber.
Tibia and fibula structure:
Bone tibia and fibula are classified as long bones with their outer surface covered by the periosteum. Underneath the periosteum is the outer shell of the long bone called the compact bone/cortical bone.
The cortical bone functions to support our body/protect internal organs/act as levers for movement/store and release bone chemicals. Beneath the cortical bone is the deeper layer of cancellous bone (spongy bone), which contains the medullary cavity and bone marrow.
Lower leg compartments
The lower leg is divided into 3 compartments by the intermuscular septa (fibrous tissue sheets) and the interosseous membrane:
Anterior (front) compartment
Lateral (outside) compartment
Posterior (backside): further divided into the deep and superficial compartments
Muscles in each compartment and their functions:
Section 2: Stress injuries - stress syndrome, stress reaction, and stress fracture in the lower leg
Medial tibial stress syndrome
Stress reaction
Stress fracture
Characteristics in lower extremities stress fracture.
High-risk Vs. low-risk stress fracture
Magnetic Resonance Imaging (MRI) classification of stress injuries
Medial stress syndrome, stress reaction, and stress fractures are terms that we frequently encounter when we talk about stress injuries. It's worth spending some time knowing each of the terms and how they relate to each other. We can better understand how to prevent the injuries and figure out what treatments are beneficial to the condition.
What is medial tibial stress syndrome (MTSS)?
Medial tibial stress syndrome (MTSS), also known as shin splints, is a common lower limb exertional injury. It happens when our body is unable to heal well under repetitive muscle contraction and tibia strain. MTSS involves injuries such as tendinopathy and periostitis.
Tendinopathy: tendinosis (collagen breaking down of a tendon)
Periostitis: inflammation of the periosteum (a membrane covering the bone). Periostitis in MTSS usually occurs together with cortical bone microtrauma.
Which muscles are responsible for medial tibial stress syndrome (MISS)?
With the current scientific evidence, we can hardly accuse any particular muscle guilty of causing MTSS. Different theories are proposing the exact cause of MTSS, with no one being proven. Example of the approaches are:
Soleus and Flexor Digitorum Longus, originating from the tibia's posteromedial (back and inside) border, are highly correlated with the MTSS injury. In particular, Soleus, which induces a traction longitudinal periostitis at the tibia.
Gastrocnemius and Soleus muscles' contraction exerts a bending force in the tibia during the push-off phase of running.
Gastrocnemius and Soleus plus the deep Flexor Digitorum Longus muscles' contraction.
Will medial tibial stress syndrome (MTSS) periostitis eventually crack the bone?
It is no doubt that the majority of MTSS periostitis is associated with cortical bone microtrauma*. Some researchers proposed that MTSS periostitis will eventually break the bone. However, some scientists argue that not all stress fractures developed from MTSS periostitis. They suggest that MTSS and stress fracture share some common risk factors, injury site, and etiology but are different in the injury development.
*22 out of 35 patients with MTSS have bone changes in the biopsy.
No matter MTSS and stress fracture are within the same spectrum of pathology. It is suggested that with early detection and intervention of stress syndrome, a fracture can be prevented.
What is a stress reaction?
The term stress reaction refers to the bone adapting to the pressure adding to it. During endurance activities such as running, muscles continue to increase in strength and exerting force on the bone. The bone is an ever-adapting structure. However, it adapts less rapidly than muscles. Muscles and tendons could adapt within weeks, whereas bone required months to catch up.
What is a stress fracture?
When the bone fails to adapt to stress, a condition called "microfractures" or "pre-stress fracture" will result; it will heal if stress factors are removed; if not, a clear fracture line could result. Stress fractures occur when the stress-induced microfracture exceeds the bone repaired rate, or people said bone resorption is faster than bone formation.
Bone resorption is when osteoclasts (demolisher bone cells) break down the bone tissues, releasing minerals (calcium) into the blood.
Bone formation/ossification is forming new bone tissue by the osteoblasts (builder bone cells).
From stress reaction to stress fracture
Stress reaction and stress fracture are a spectrum of conditions. One end is minor pain along the tibia/fibula bone that can elicit after exercises. A slight decrease in activity level or change of footwear can decrease the pain.
The other end of the spectrum is a stress fracture with severe pain that may make you unable to continue the sports activity. You may also feel pain at any other time, including daily ambulation or during rest.
In between the two extremes is a variation of symptoms. It could be a recurrence of pain when the activity intensity hits a certain level. Over a while (varies from months to years), if the activity level remains the same, there may be some structural change at the cortical bone, such as increased thickness.
Characteristics in lower extremities stress fracture:
Stress fractures can occur in any bone.
Lower extremities account for 80% to 90 % of the total stress fracture.
Injury locations such as the pelvis, femur, tibia, fibula, or metatarsals.
Commonly occurs in individuals who participate in endurance and high-load activities such as running/hill-running/marching/dancing.
Tibia
The most common lower extremities stress fracture, which accounts for 23.6%.
The majority are low risk and located posteromedially.
Commonly seen in athletics, military personnel, and recreational sports participants (3%-35%).
Anterior tibial stress fractures are less common yet considered high risk due to the high incidence of nonunion.
Fibula
Occur around 7%-12%.
Pain is commonly localized to the lower fibula (7cm to 10 cm above or proximal to lateral malleolus)
Fibula does not play many weight-bearing roles; it is suggested that muscle imbalance is one factor that leads to a stress fracture.
High risk Vs. Low-risk stress fracture
A stress fracture can classify into high and low risk with different characteristics as follow:
Using Magnetic Resonance Imaging (MRI), stress injuries can classify into different level according to severity:
Section 3: Diagnosis of the lower leg stress injuries
History
Clinical examination
Imaging
If you suspect you are suffering from lower leg stress injuries, always consult medical advice for a proper diagnosis. It is important to differentiate other lower extremity injuries/exertional pain such as compartment syndrome, muscle tears, fascial defects, venous thrombosis, artery/nerve entrapment, infection, or tumor from stress fractures.
History:
Exercise routine:
A thorough understanding of sports activity routine is required to understand the situation, e.g.:
Exercise intensity
Frequency
Duration
Pace
Training terrain
Footwear
Any recent change in training routine: A drastic increase in training intensity or increased repetitive exercises without adequate rest is prone to stress injuries.
The behavior of pain:
Pain location: vague or localized pain
Pain intensity
Pain frequency
Pain duration
Onset and ceasing of pain
With or without resting pain
Refer pain, e.g., a proximal tibia stress fracture may refer to pain in the knee.
General health conditions, e.g.:
Nutritional disorder
Hormonal disorder
Sleeping disorder
Drinking/smoking habitats
Clinical examination:
General sign and symptoms of stress fracture in lower limbs:
local tenderness on injury site (65.9%-100%)
Local edema on injury site (18%-44%)
Pain during ambulation (81%)
Specific sign and symptoms of medial tibial stress syndrome:
Vague pain along the middle-lower tibia
Without edema
Specific sign and symptoms for tibia:
Pain during weight-bearing activities on the tibia shaft
pain with percussion.
Specific sign and symptoms for fibula:
Localized pain in fibula near/slightly above the ankle bone.
Core, pelvis, and leg muscles examination for:
Muscle weakness
Muscle tightness
Dysfunction
Special test /function test:
Hop test:
Single leg hopping that produces localized pain in patients with stress fractures can be used as functional diagnostic tests. However, its accuracy needs further validation. A pain provoke single-leg hop test is a common finding in people who developed stress fractures (70%-100%) as well as other stress syndromes (45.6%)
Tuning fork test (for stress fracture):
Apply a tuning fork to the injury site to provoke localized pain. This test needs further validation (one research reported a 75% sensitivity and 67% specificity)
Sensitivity: the proportion of positives that are correctly identified
Specificity: the proportion of negatives that are correctly identified
Imaging
Imaging alone cannot be used as the only tool to diagnose stress injuries; they have to be used in conjunction with a thorough history and clinical examination.
Plain radiography: X-ray
Usually, an x-ray is the first imaging modality to consider due to its low cost and widely available, however, with poor sensitivity of about 10% in the acute stage. X-ray provides information about fracture line, periosteal bone formation, and cortical margin after 2 -3 weeks of symptoms. Its sensitivity increased to 30%-70% after 3 weeks as it takes time for the cortical irregularities and periosteal reactions to become evident.
After an initial x-ray with a negative result of a stress fracture and without the urgency of speedy diagnosis. With the caution that the diagnosis is provisional and exercises intensity should reduce/avoid stress. Another X-ray can be repeated after 2-3 weeks.
Computer tomography (CT)
Regularly used for bone pathology. However, CT is not preferred due to its higher radiation exposure and lower sensitivity.
Bone scan/ bone scintigram
Highly sensitive (74%-100%) but seldom used to diagnose stress fracture due to high radiation exposure. The increased bone activity resulting in the bone scan may indicate focal infection/tumors.
Magnetic resonance imaging (MRI)
Higher cost and less readily available compared to X-ray. MRI is equally or highly as sensitive as bone scintigram. Currently used as a confirmation test and is the next imaging technique considered if X-ray showed negative results. The advantage of MRI is its ability to display images of soft tissue, bone edema, and reactive bone remodeling (an early sign of stress fracture). Also, MRI has no radiation exposure.
Ultrasonography
Becoming more widely available. Pilot studies showed a sensitivity of 83.3% and a specificity of 75%. Its advantages are low cost and no radiation exposure.
Steps of using imaging to diagnose stress injuries:
Since the first onset of pain during exercises, the following steps can be employed by the medical team for the diagnosis of stress injuries:
Section 4 Contributing/risk factors to lower leg stress injuries:
Biological factors
Activity factors
Biomechanics/musculoskeletal factors
Biological factors increasing the risk of stress injuries:
Gender: Female 1.5-3.5 times increased risk for progression to stress fractures in the posteromedial tibia; female athlete triad (amenorrhea/osteoporosis/eating disorder), menstrual irregularities.
Maturity: immature bone when growth is not complete and bone mineral density is low.
Nutritional deficiencies: Such as calcium/25 hydroxyvitamin D and/or eating disorder.
Smoking
Consuming more than 10 alcoholic drinks per week.
Medication-induced deficiencies: such as antacids/steroids/antidepressants
Radiation
Imbalanced hormones
Sleep deprivation
Collagen anomalies
Activity factors that increase the risk of stress injuries:
Type of activity: Common in endurance or ballistic sports such as distance running/marching/basketball/football/dancing. Stress injuries account for 10% of total sports injuries, of which 30% occur in runners (20% incidence in track and field athletes).
Activity level: Sudden increase in running mileages without adequate rest, which means training is too much and/or too fast.
Equipment: Such as wearing shoes that wear and tear too much or without proper support.
Biomechanics/musculoskeletal factors that increase the risk of stress injuries:
Bone:
Bone composition: A study showed low bone mineral density increases bone stress injury healing time in male runners; other researchers correlated low bone mineral density and medial tibial stress syndrome.
Bone size: Thinner cortex bone
Muscles:
Smaller calf size
Muscles imbalance: such as imbalance hamstrings to quadriceps ratio
Core/pelvis/leg muscles weakness: such as weakness of the gastrocnemius, soleus, and plantaris muscles, are commonly associated with increased medial tibial stress. Weakness in hip and pelvis muscles should also be checked, as they are essential in maintaining lower limbs' stability.
Tight muscles: such as gastrocnemius, soleus, plantaris, and hamstrings
Coordination:
Poor balance and joint proprioception: causing fatigue of stabilizing muscles
Alignment that increases the risk of stress injuries:
Knee angle: genu valgus greater than 15%
Hip angle: excessive hip adduction and external rotation
Tibial torsion
Ankle position: Hyper-pronation/excessive inward rotation can cause overexertion of the tibialis posterior/flexor hallucis/digitorum longus muscles that stabilize the foot.
Varus ankle/forefoot
Rear-foot eversion
Foot arch abnormalities: high foot arch
Leg-length discrepancy
Section 5 Treatment to lower leg stress injuries:
Acute stage
Return to exercises
Preventing stress injuries
Visit healthcare professionals to arrange a tailor-made rehabilitation plan. Stress injuries are overuse syndrome that can involve multiple causes. Efficient treatment requires careful examination to tackle the underlying contributing factors.
Consult your doctor for supplements such as vitamin D/calcium or hormonal treatment/other underlying health issues.
1 st phase /acute stage:
Ice (15mins each, 3 times/day)
Anti-inflammatory medicine (In caution and ask your doctor as it can be risk factors for stress fractures)
Rest (2-8 weeks depending on the severity of injury)
Weight-bearing as tolerated/assisted with walking aids: Caution: Overprotection or avoiding weight-bearing sometimes negatively impacts recovery speed or leads to other complications. You should follow healthcare professionals' advice.
Maintain cardiovascular endurance by running in water/ swimming if land training is prohibited.
2nd phase /return to exercise:
When pain-free during daily weight-bear activities, you can focus on gradually recovering to practices with modification on the training regimen.
Several tips in the following paragraphs:
Use low-impact and cross-training exercises: doing exercises other than your primary sport to improve the overall performance.
About intensity: Running returns to normal gradually under supervision (3-6 weeks). Starting with 30%-50% pre-injury (regarding the individual pre-injury level) and progress using the 10% rule: increase running mileage and intensity no more than 10% per week—progression guided by pain, range of motion, signs, and symptoms.
Modifying running surface? Some people who are suffering from lower leg stress injury benefit from avoiding hard and uneven surfaces. However, this is not the magic curer; running on a soft surface can increase the bone's loading (demand more leg stiffness). Scientific researches remain controversial on which training surface significantly increases or decreases the risk of stress injury. The most important tip is the overall force adding to the bone should not exceed its healing rate. You can experiment with what surfaces are beneficial to you. If you don't have a choice on the workout surface, modify the training intensity.
Wear good shock-absorbent shoes (change shoes every 6 months or 300-500 miles).
Use orthotics if indicated.
Gait retraining/ running posture modifying if indicated.
Preventing stress injury:
Design training protocol that suitable for yourself with the help of coaches or trainers, taking running as an example:
The traditional recommendation is to increase 10% mileage per week.
You can also consider:
10% - 20 % mileages down week for every 3-4 weeks.
20%-30% increase in mileages in 3-4 weeks with constant mileages in the intermittent week.
Please also remember you can increase the intensity by less than 10% per week or having more than 1 week down. Always consider your body's condition and take your time; pushing too hard and ignoring signs of injury will eventually cause more time off training. The idea is to allow adequate time for the bone to adapt to the increased loading.
It is a good idea to keep a record of your running log to time your progression. If stress injuries develop, a past training record can be used for rehabilitation or return to sports guidelines.
Modifying biomechanical factors:
Certain risk factors such as genetics, gender, or body alignment that we cannot modify. However, there are some factors we can definitely work on to condition ourselves better to prevent injury or improve performance; they are:
Muscular strength/endurance training: strengthening/endurance exercises in the pelvis, hip, quadriceps, shin, and calf. Remember we talk about the calf's small cross-sectional areas as one of the risk factors of stress injury? It is commonly believed that strength relates to cross-sectional area. Therefore, strengthening calf muscle is beneficial to reduce stress injuries.
Balance/proprioception training: a key in injury prevention. It improves the efficiency of joint and postural stabilizing muscles and helps the body run on uneven surfaces.
Flexibility: perform regular stretching/foam rolling in the gastrocnemius, soleus, hamstrings. A stretching routine can be introduced into a daily routine (not just before exercises) as it is essential to maintain an adequate range of motion to perform your sports.
Exercises suggestion for lower leg stress injuries prevention:
You can perform the exercises below 2-3 times per week.
Pelvic Bridge exercise:
Lying flat on the floor, bend your knees with your feet on the floor. Lift your buttock until your body is in a straight line; hold 10 seconds for 10 repetitions.
Progression:
Increase difficulty by exercising with one leg; keep one of your knees straight and lift your buttock until your body forms a straight line. Hold 10 seconds for 10 repetitions.
Eccentric calf exercise:
Start the exercise with double legs. Stand on the edge of a step, lower your body slowly and raise on your toes. Repeated 15-20 times.
Progression:
Increase difficulty by exercising in a single leg, lowering your body in one leg (right side), and raising to tip-toes with another leg (left side). Repeated 15-20 times.
Further progression can be made by adding weight using dumbells/weight on shoulders.
This exercise required full weight-bearing. Start the activity only when you are allowed to bear weight on the injured leg. Consult medical professionals if you have any problems.
References:
1.Aetiology and mechanisms of injury in medial tibial stress syndrome: Current and future developments
5.Steven Roy, Richard Irvin Sports medicine prevention, evaluation, management and rehabilitation. Prentice-Hall 1983. Chapter 21.
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