Muscular Calf Injuries in Runners

Abstract

Calf pain is a common complaint among runners of all ages but is most frequent in masters athletes. This article focuses on injuries to the triceps surae or true "calf muscles." The most common calf injury is a tear of the medial gastrocnemius muscle (Tennis Leg) but other structures including the lateral gastrocnemius, plantaris and soleus also may be the cause of muscular pain. This article looks at the presentation, evaluation, and treatment of these injuries. We also highlight some examples of musculoskeletal ultrasound which is a valuable tool for rapid diagnosis of the cause and extent of injury.

Introduction

Calf pain affects many athletes and occurs commonly in runners (¹⁶). Calf pain arises from numerous etiologies including vascular, neurologic, skeletal, and musculotendinous sources. Calf pain in runners usually results from musculotendinous origins, with the gastrocnemius among the most common of all muscle injuries (¹⁷). The purpose of this article is to further characterize musculotendinous injuries of the calf other than those of the common Achilles tendon.

Anatomy Review

Calf pain usually occurs in the posterior compartments of the lower leg. The posterior leg has two compartments: the deep and superficial. The deep posterior compartment contains the popliteus, flexor halluces longus, flexor digitorum longus, and tibialis posterior and injuries to these typically present with pain in the shin or near the ankle. This article focuses on the superficial posterior compartment which contains the true “calf muscles” which are termed by most anatomists as the triceps surae. The three muscles of the triceps surae are the gastrocnemius with medial and lateral heads, plantaris, and soleus.

The gastrocnemius and plantaris are biarticular muscles responsible for both knee flexion and ankle plantar flexion. The soleus is a uniarticular muscle responsible for plantar flexion. The plantaris is generally considered a vestigial muscle (³) and provides a weak contribution to knee and ankle flexion when it is functional. The gastrocnemius originates from both the medial and lateral femoral condyles and consists of two distinct heads. Although the gastrocnemius has a mix of fibers, more are fast twitch (type 2) muscle fibers allowing for explosive/powerful contractions. The soleus is primarily composed of slow twitch (type 1 muscle fibers) and is the key muscle for endurance running. The triceps surae inserts on the calcaneus via the common Achilles tendon.

Innervation of the triceps surae is from the tibial nerve with the plantaris contribution from the L5-S1 nerve roots and the soleus and gastrocnemius contributions via the S1-S2 nerve roots (^2,20,23).

Epidemiology of Muscular Calf Pain in Runners

Injuries to the calf complex occur across all age ranges, athletic abilities, and competitive levels. In the general population, the highest risk group is a poorly conditioned male in the fourth to sixth decade of life usually while doing recreational activity (^3,9). Approximately 20% of the patients report prodromal calf soreness before calf injury. Cavus feet have an association with Achilles tendon injury but not specifically injuries to calf muscles. Although these seem logically related, evidence has not emerged to date. No other specific anatomical risks predict calf injury (^3,7,9).

Among runners, master athletes have a disproportionately high risk for calf injuries, whereas younger runners have higher rates of Achilles tendinopathy (¹⁶). In a study of more than 2000 running-related injuries, gastrocnemius injuries were disproportionately distributed among sex with 70% of the injuries occurring in men. In the same study, gastrocnemius and soleus muscle injuries accounted for only 1.3% of all lower-extremity injuries, and these muscular injuries appear to occur approximately 25% as often as injuries to the Achilles tendon proper (27 vs 96) (²⁶). Factors that contribute to the age and sex differences are unclear but are likely due to age and sex differences in fatigability, cellular metabolism, and tendon elongation/stiffness (^10,11,21).

In multiple imaging studies of Achilles and calf muscle injuries, there appears to be a predominance involving the medial head of the gastrocnemius which is involved in 58% to 65% of all cases; the lateral head of the gastrocnemius in 8% to 38% and the soleus in 58% to 66% (^4,12). Plantaris muscle injuries are the least common injuries and only accounted for 2 (1.4%) of 141 patients in one study (⁵). Injuries to the medial calf often result in swelling in both the medial gastrocnemius and the soleus. The most common location of pathological swelling in Delgado’s study was at the fascial intersection of the medial gastrocnemius and soleus as it merges with the proximal Achilles tendon (66% of patients).

Clinical Findings

A thorough history and physical examination should be performed for calf injuries focusing on potential mechanism of injury (acute vs overuse) and other secondary trauma associated with the injury. For most gastrocnemius and popliteus injuries, there is an acute event that occurs after sprinting or jumping. This led to the common name of “Tennis Leg” because these injuries frequently occur when a tennis player sprints for a ball. Thus, in runners, the injury more frequently arises during faster interval training, racing, or high-speed tempo runs. Soleus injury comes on with fatigue or overtraining so that the runner may not recall an acute event but experiences progressive calf pain that ultimately becomes too limiting to allow normal running. Marathoners often have onset within the first 24 h after the long run on their training schedule or after a race.

History and specific aspects of examination help limit the differential diagnosis to muscular calf injury. If historical features indicate risk factors for venous thromboembolism (VTE) and deep venous thrombosis (DVT), reproducible claudication-like symptoms (popliteal entrapment syndrome and exertional compartment syndrome) or radicular symptoms into the lower extremity, these entities require exclusion. If an athlete had fever, systemic symptoms, or a history of diabetes mellitus, the evaluation would need to screen for infections or myonecrotic causes for deep calf pain. Lateral calf pain, particularly with any sensory change or weaknesses, focuses attention on entrapment of peroneal or sural nerves.

If an athlete experiences severe acute pain, marked swelling or the calf injury appears to be a complete rupture with a muscular defect, careful monitoring of the evolution of the symptoms after the injury is important to be sure that the athlete is not developing a compartment syndrome or DVT.

Physical examination should focus on appearance, neurovascular status of the extremities, range of motion, and function of the knee and ankle joints. The severity of injury will determine the type of findings on examination. Milder injuries will show tenderness to palpation, pain with resisted muscle testing but no visible swelling, discoloration or defects. More severe injuries show significant tenderness to palpation, discoloration and swelling, and sometimes a visible defect.

Tenderness for gastrocnemius injuries typically localizes at the distal insertion of the medial or lateral head into the proximal Achilles fascia. Tenderness for soleus injury is palpated deep and often distal to the muscle bellies of the gastrocnemius on either medial or lateral leg. Popliteus injury tenderness is deep and often at the intersection of the two gastrocnemius heads or along medial proximal Achilles tendon.

Ensuring the Achilles tendon is intact by performing the Thompson’s test is imperative. Thompson’s test has been shown to be 96% sensitive and has a 98% positive predictive value for Achilles rupture (¹⁴). Physical findings for DVT with exception of unilateral calf swelling are poor predictors for DVT but deep tenderness, a palpable cord, cuff compression sensitivity, and more diffuse swelling during both the acute phase and at subsequent office visits are worrisome for thrombosis (²⁷). Caution should be exercised regarding empiric anticoagulation use before confirmation of DVT because bleeding from gastrocnemius injury has been severe enough to result in acute compartment syndrome as demonstrated in specific case reports (^8,24).

Imaging Findings

Imaging is generally not required for acute calf injuries. However, musculoskeletal (MSK) ultrasound (US) can be useful for diagnostic confirmation and for determining the extent of damage. X-rays are not generally indicated unless there is an associated traumatic component to the injury or symptoms that arouse suspicion for a systemic process. Magnetic resonance imaging (MRI) should be reserved for situations where the diagnosis is unclear. For soft tissue injuries, including MSK pathology, MRI is considered the gold standard for assessing soft tissue injuries in the United States. However, MSK US has been shown to have similar sensitivity and specificity for muscular injuries, particularly superficial injuries (¹⁸). Because of lower cost and point of care diagnostic access, MSK US has become the initial diagnostic test in centers in the United States and internationally that have practitioners skilled in diagnostic US.

There is a poor predictive value between the initial imaging findings on US and MRI for predicting return to play and risk of reinjury. However, imaging can be useful, especially in advising the competitive runner when determining return to high-level competition/training. When structural damage persists on US, most clinicians would caution the runner against full training, although it is important to share with the athlete that there is no strong evidence to support this (^25,28).

Mild calf injuries show minimal if any change on US or MRI. US features that clinicians may identify in the office setting include:

• Diffuse hypoechoic changes in specific muscle groups
• Disruption of normal fiber patterns
• Localized hypoechoic changes suggestive of hematoma or swelling in fascial layers
• Echogenic material in a noncompressible vein suggestive of DVT (^27,29).

Some examples of US changes seen in injured runners are shown in Figures 1 to 4.

Figure 1: Hematoma (circle) in fascial plane between medial gastrocnemius and soleus. This is the most common location of pathological swelling after mild to moderate injury. Longitudinal scan. Image may only be used with permission from Karl B. Fields, MD.

Figure 2: 14-cm-long hematoma after high-grade medial gastrocnemius rupture longitudinal scan. Gastrocnemius (star), hematoma (circle). Distal tear—arrow at myofascial junction. Image may only be used with permission from Karl B. Fields, MD.

Figure 3: Transverse view of same tear shows it extends across entire calf gastrocnemius (star), hematoma (circle). Image may only be used with permission from Karl B. Fields, MD.

Figure 4: Organizing hematoma and tissue healing in subacute phase of medial gastrocnemius rupture transverse and longitudinal comparison. Normal gastrocnemius (star), organizing hematoma and tissue (arrow); soleus (circle). Image may only be used with permission from Karl B. Fields, MD.

Etiology and Clinical Findings

Gastrocnemius Injuries

Gastrocnemius injuries are most commonly associated with ballistic movements while the ankle is flexed and the knee is extended (eccentric contraction of the calf) (¹⁹). Often times, athletes report feeling a sudden tear or pop with acute pain. If a high-grade injury is sustained, a palpable defect can often be appreciated. Injuries to the medial head of the gastrocnemius muscle most frequently occurs at the musculotendinous junction. “Tennis Leg” is a common term that is used to describe this injury.

Soleus Injuries

Soleus complex injuries are typically due to overuse mechanism and occur due to repetitive dorsiflexion of the ankle with the knee bent such as with uphill running. Due to being an overuse injury, soleus strains are usually reported as having a slow, insidious onset. However, acute injuries can occur in fatigued runners and once again usually will occur with uphill running or toward the end of a longer run.

Plantaris Injuries

Plantaris injuries are the least common calf complex injuries. They typically occur due to a similar mechanism as a gastrocnemius tear and are associated with ballistic plantarflexion with the knee extended. Runners may hear a pop when the plantaris ruptures.

Differential Diagnosis

Other etiologies of calf region pain can come from multiple sources including musculotendinous injuries from adjacent structures and from neurovascular etiologies. Adjacent structures include the popliteus muscle as it crosses the proximal calf and deep posterior compartment structures. Popliteal injuries will typically localize to the posterior knee or proximal leg. This injury is typically associated with downhill running/walking and is due to tibial rotation with an extended/hyperextended knee. Deep posterior compartment pain commonly localizes along the medial posterior tibial border or shin or along the tarsal tunnel but can cause pain in the calf region. Careful examination and muscle testing techniques confirm the diagnosis.

Neurovascular injuries can be limb or life threatening. Acute compartment syndrome can complicate severe MSK injuries due to hematoma collection or occult fracture and should be considered in the patient with worsening swelling, tenseness in the calf, pain, pallor, paraesthesias, or changes in pedal pulses. Exertional compartment syndrome is a possible presentation of posterior calf pain; however, it does not commonly affect the superficial posterior compartment. DVT also can be seen in conjunction with calf injuries, and patients’ risk should be assessed, and lower extremity venous Doppler US should be considered. Popliteal Artery Entrapment can mimic soleus strains because it often presents with claudication-like symptoms that resolve with rest and predictably returns with resumption of activity after rest. Vascular surgery consult, exertional ankle brachial index, and or angiography should be considered.

Treatment of Calf Injuries

Return to play ranges from a few weeks to 3 to 4 months after most injuries to the posterior calf depending on the grade/extent of the injury. The initial phase of care consists of rest (either complete or relative), ice, compression, and elevation. The goal of ice, compression, and elevation is to reduce hematoma formation or worsening and to improve blood, lymphatic, and interstitial flow at the cellular and regional levels to promote healing. In more severe injuries, a few days of crutch walking may be required. No evidence points to use of cam walkers but they are often used in severe injury to help more quickly facilitate weight bearing.

Treatment interventions that may facilitate return to running include compression sleeves. Ones that reach 20 to 30 mm Hg are felt to reach the physiologic level sufficient to help reduce swelling and promote healing. Limited evidence based medicine (EBM) supports that they speed return to running by up to 7 d (¹³).

Heel lifts often lessen the pain of walking in patients with Achilles and calf injury. We routinely use these and continue them for 6 to 12 wk after injury.

Standard eccentric calf raises from a step to facilitate the rehabilitation of Achilles tendon injury were described by Mafi et al. and have good EBM to support efficacy. These have been used for calf injury rehabilitation because the calf and Achilles are part of a continuous musculotendionous complex (^6,15). More recent EBM demonstrates that the concentric progressive resistance calf raises effectively rehabilitate Achilles injury and also could be applied for calf injury based on the same rationale (¹).

Medical interventions to date lack EBM to prove efficacy in calf injury. Biologic therapy with platelet rich plasma, whole blood or stem cells has not demonstrated benefit to date. Biologic modification with topical nitroglycerin has moderate EBM for benefit in Achilles injury but has not been studied in calf injury (²²). At our sports medicine center, we have used this for numerous calf injuries (based on the similarity of Achilles and calf function) with what we feel are positive results. No randomized control trials exist to date to support this approach.

Return to running is based on clinical judgment after calf injury. We suggest a progressive program based on the extent of injury and the objective evaluation of the patient in the office. When a patient with calf injury can walk without a limp and do 15 single leg calf raises with minimal pain, we will place a heel lift in their running shoe and apply a calf compression sleeve. If they can then run slowly with no limp, we will allow them to do easy running as they begin their rehabilitation from the injury. We would like to see the athlete able to do 3 sets of 15 single leg heel raises with knees bent and knees straight with no pain and demonstrate the ability to run slowly for 30 min continuously without pain or limp before allowing return to full training. This approach has been documented in greater detail in a published review (²³). Evidence for specific clinical return to running programs to date is based on expert opinion and has not been studied.