Differentiating why an athlete is experiencing lower leg pain can be difficult to ascertain as a healthcare provider. Moreover, it is of utmost importance to make an accurate diagnosis to ensure these injuries do not become more serious. In this clinical pearl, we are going to help you understand how to differentiate 3 common causes of anterior, lower leg pain which include: shin splints, stress fractures, and exertional compartment syndrome. We will follow up this clinical pearl with a part 2 that will be focused around the treatment component of lower leg pain in athletes!
When a patient is being evaluated for lower leg pain, 3 competing diagnoses are often included within the differential diagnosis process which are:
-Medial Tibial Stress Syndrome (Shin Splints)
-Exertional Compartment Syndrome
Let’s discuss the main differences between these so when evaluating patients you understand how these different conditions may present.
Shin splints. Those daunting words that hang over our heads. Whether we may want to admit it or not, it’s that diagnosis we are not quite as thrilled to see come through our door as physical therapists, athletic trainers, or sports medicine physicians. This lower leg injury often due to overuse is a difficult one to rehabilitate for many reasons, one of which being its obscurity. Shin splints, which is better known as ‘medial tibial stress syndrome’, is an injury more common in endurance athletes such as runners, as well as athletes involved in jumping sports such as basketball or volleyball, who are placing large amounts of stress with high volume through their lower extremities.
Presented in an article by Winters et al, Medial tibial stress syndrome (MTSS) is currently defined as pain that is present along the posteromedial border of the tibia that occurs during exercise or pain with palpation over a 5 centimeter or greater area of the posteromedial border of the tibia. As previously stated, this injury is more commonly seen in individuals who place a large amount of stress through their lower legs, with the highest incidences being present in long-distance runners, dancers, and military personnel.
What is challenging about this condition is that there remains an ‘unknown’ as to what exactly causes shin splints, and what exactly occurs from an anatomical and physiological perspective. The following hypotheses have been suggested within research conducted by Couture and Karlson:
–Soleus muscle fascial connection to the bone: The soleus fascia has connections to Sharpey fibers of bone that may be disrupted leading to injury.
–Soleus muscle eccentric fatiguing: The repetitive stress of the lower leg potentially causes tibial ‘bowing’, which leads to overloading bone-remodeling capabilities of the tibia
–Traction or pulling on tibia: Some authors have supported that MTSS is due to traction-based periostitis (inflammation of the bone), mainly from the posterior tibialis as well as other ankle invertors that help stabilize the medial longitudinal arch; however, there has been fight back against this notion. Moen et al conducted a systematic review in 2009 which concluded MTSS is due to bony overload. In addition, imaging studies have corroborated the tibial cortex becomes osteopenic and bone marrow is involved (Aoki et. al 2004).
Usually, an athlete is going to complain of an insidious onset of pain in the lower leg with an increase in activity. Normally, the pain is much worse with stress-related activity. The pain can be present either at the medial aspect of the tibia or even on the anterior aspect of the tibia. The pain is usually described as a deep, dull boring pain, but if becoming more severe, it can be described as sharp.
Clinical Pearl – Incline Training: Runners who have been training on an incline or doing a lot of hill training should increase suspicion due to increased usage of the ankle dorsiflexors originating from the anterior compartment of the lower leg.
Clinical Pearl – Muscle Resistance Testing: Pain with resisted inversion and/or ankle dorsiflexion that causes activation of the anterior compartment lower leg muscles involved in shin splints can also raise diagnostic suspicion.
Clinical Pearl – Area of Palpation: Shin splints are more likely to be painful within a larger region of the tibia.
Clinical Pearl – Pain Pattern: Pain may be worse in the morning with shin splints as the muscles of the lower leg tighten up overnight and may lead to discomfort when an individual is starting out their day.
Stress fractures occur when there is repetitive load to areas of the body without proper recovery, which leads to an imbalance between bone formation and absorption. Moreover, the osteoclasts (breaking down bone cells) start to overpower the work of the osteoblasts (building up bone cells). Most of these will occur in the cortical region of the bone, the diaphysis of long bone, or the shell of square bone where the remodeling process is slower.
Clinical Pearl – Bones More Prone to Poor Healing: It is also important to note that some stress fractures are more prone to poor healing if they are in areas of higher loading and/or decreased vascular availability. Some examples include the talus of the ankle, 5th metatarsal zone 2 (Jones fracture), navicular, and scaphoid of the hand. The tibia is reported as the most common site of a stress fracture, followed by the tarsals and metatarsals. You can read more on this topic in an article by Hack et al.
Similar to shin splints, usually athletes will have an insidious onset of pain that is worse with activity and better with rest. In this case, the anterior tibia will usually be tender upon palpation.
Clinical Pearl – Area of Palpation: In contrast to medial tibial stress syndrome, stress fractures usually are going to be more intense in regards to pain, and more focal in regards to where the pain is located, whereas shin splints have more of a diffuse, aching type of pain.
However, keep in mind, some studies have shown that individuals with lower-grade stress reactions may have more diffuse tenderness, whereas if it is a higher grade injury, the tenderness may become more localized. This was exemplified in a study by Fredericson et al, which showed that runners who had a grade I or II injury that was revealed on MRI had diffuse tenderness on the posteromedial aspect of the tibia, whereas female runners with a grade III or IV injury had localized tenderness of the medial tibial diaphysis with that was reproduced with direct percussion.
In addition, stress fractures are more often unilateral, whereas shin splints can often be bilateral. Yes, they both are related to an increase in workload; however, stress fractures have more localized, sharp, intense pain reporting than shin splints.
Imaging does play an important role in the diagnosis of a stress fracture. If you want to quickly screen a patient before sending him or her for a referral for advanced imaging, a tuning fork can be utilized over the tender area of palpation; however, this is not valid nor reliable, and should NOT be relied upon solely for diagnosis.
Clinical Pearl – Don’t Rely on X-Rays: Plain films (X-Rays) often do NOT show evidence of stress fractures!
Bone scans or MRIs are more sensitive and specific than plain films. In fact, Kiuru et al corroborated in a study that X-rays are only about 10% sensitive in the early stages of a bone stress injury (BSI) injury! What is also important to note is that advanced imaging such as an MRI may not actually show evidence of a fracture, but a stress reaction. What is the difference? A stress reaction demonstrates cellular changes within the bone, such as increased bone turnover and periosteal edema, but does not show an actual fracture line. This can be helpful with a diagnosis for physicians if they begin to see changes within the bone before a fracture occurs.
Therefore, if you have a patient that has had plain film imaging, yet you still have a hunch that a stress reaction may be present, do not be afraid to speak your clinical mind to an orthopedic surgeon or sports medicine physician! If that individual goes back to running or another sport with an underlying stress fracture, a microfracture can become a macrofracture, which becomes a much bigger issue, literally!
As healthcare practitioners, we are more concerned with stress fractures at the distal one-third of the tibia. A small stress fracture undetected here can lead to a larger fracture across the horizontal aspect of the entire tibia, leading to longer recovery and poorer prognosis.
Exertional compartment syndrome of the lower leg is not as common in relation to MTSS or stress reactions, yet they still can occur. If an acute compartment syndrome occurs, it is a medical emergency. The mechanism as to how compartment syndrome occurs is thought to be due to fascial constriction as there is an increase in blood flow to muscles within a specific compartment. As that constriction process occurs, there is less blood flow available to that area of the body, which results in pain.
A hallmark description of individuals with compartment syndrome is pain that occurs at a specific period of activity. As the muscles within the specific compartment involved become overworked, there will be an increase in pain. The pain will resolve when the activity is stopped. The pain is usually described as burning, pressure, and potential numbness/tingling if there is nerve involvement. Moreover, weakness may be present in the muscles involved.
Example: A patient who has pain when running that is located in the lower leg into the dorsal aspect of the foot that begins after 20 minutes of running and is described as numbness, pressure, and burning. The pain stops about 20 minutes after stopping the run.
Although as a physical therapist or athletic trainer you will not perform this, intracompartmental pressure measurements is the gold standard for compartment syndrome diagnosis. The take home is if you have a patient who is describing symptoms of pressure, numbness, tingling, or burning, and/or potential weakness, suspicion should be raised for compartment syndrome.
Risk factors in regards to MTSS has also been conflicting within research. A recent case-control study by Mohen et. al in 2010 looked at risk factors to increase reliability for diagnosing MTSS. After performing a multivariate regression analysis, the following findings were supported for risk factors:
–Increased ankle joint plantar flexion: The proposed theory behind this is that increased ankle joint plantar flexion may predispose an individual to more of a forefoot landing with running or other sports related activity, which can place more stress through the tibia
-Decreased hip joint internal rotation range of motion: Changes in hip joint range of motion may alter running kinematics leading to excessive loading at the tibia. The contrary argument can be made, which is has by Burne et. al in 2004 that increased hip IR was a risk factor for MTSS. Regardless, we know that if someone has mobility deficits within one area of the body, other areas of the body can take more, sometimes too much load.
–A positive navicular drop: Increased foot pronation may also place more stress on the medial aspect of the tibia.
Other studies have also supported increased BMI, excessive foot varus, female sex, and training errors. We have often discussed that overuse injuries, especially in runners is often due to training errors.
Training errors related to running has been related to an abrupt increase in volume, duration, and/or frequency of the activity, switching terrain to a harder surface, and excessive hill training. Moreover, the combination of running on hard surfaces and downhill places more eccentric load and ground reaction forces through the body.
Intrinsic risk factors include: Caffeine intake, smoking and/or alcohol usage, and nutrition including Vitamin D. The female athlete triad is an intrinsic risk factor in female athletes due to the lower estrogen state that alters the bone cellular response to physical stresses on the body.
The research behind Vitamin D and the risk for stress fractures has continued to be investigated. A blinded RCT by Lappe et al showed female Navy recruits who had calcium and Vitamin D supplements were 20% less likely to suffer stress fractures. Moreover, Tenforde et al conducted a systematic review, which concluded that females who consumed at least 15oo milligrams of calcium each day demonstrated the biggest reduction in risk of developing stress fractures.
Supplements that increase muscle volume such as creatine or anabolic steroids may increase the risk of developing compartment syndrome. Similar to stress fractures and shin splints, alterations in biomechanics during running or athletic activity may also predispose on to the development of compartment syndrome. In addition, excessive eccentric loads may increase risk as this can lower the pliability of the fascia.
Take-Home: With the role of a physical therapist, strength and conditioning coach, or athletic trainer, it is recommended to ensure the patient is following up with their healthcare provider to receive a proper medical workup ultimately deciphering if any risk factors can be reduced.
A detailed subjective history from your athletes in addition to signs and symptoms that are present will help you differentiate shin splints from stress fractures and/or a compartment syndrome. In the next part of this clinical pearl series, we will discuss how to manage lower leg injuries and get your athletes back on the playing field safely!