SOLEUS MUSCLE INJURY “The Betrothed”, oil on canvas, 1892, John William Godward, Guildhall Art Gallery London. To the trained Artistic eye, John William Godward’s beautiful painting the “betrothed” shows its elegant subject in one of his most classical, “lazing in the Sun”, poses whilst she dreamingly admires her newly acquired ring. To the trained eye of the Physiotherapist, she also presents the “classical poses” required for the proper examination of the gastrocnemius muscle and the soleus muscle! Her right knee lies extended - the classical pose for a gastrocnemius assessment - and her left knee lies flexed - the classical pose for a soleus muscle assessment! - a true “classic” all round! SOLEUS MUSCLE INJURY Introduction The soleus muscle is one of the three muscles of the calf. It is injured less commonly than the gastrocnemius muscle, though its true incidence may be under reported. Its signs and symptoms can be more subtle than those of a gastrocnemius muscle injury. Differentiating injuries of the soleus muscle from those of the gastrocnemius muscle however is important for both treatment and prognosis. Anatomy The calf muscles consist of three separate muscles; the gastrocnemius, the soleus, and the plantaris, whose aponeuroses unite to form the Achilles tendon. The action of the soleus muscle , is plantarflexion of the foot. The soleus specifically plays an important role in maintaining standing posture; if not for its constant pull, the body would fall forward. In upright posture, it is largely responsible for pumping venous blood back into the heart from the periphery, and is often referred to as the “soleus muscle pump”. It is supplied by the tibial nerve. See also Appendix 1 below. Pathology Unlike the gastrocnemius the soleus is considered low risk for injury as it crosses only the ankle and is largely comprised of type one slow twitch muscle fibers. Sites of injury: In comparison to injuries to the Gastrocnemius muscle, (most commonly its upper media; head) - injury to the soleus muscle s more commonly seen lateral and more distal in the calf. Complications: Premature return to sport may result in a prolonged recovery or incomplete return to pre- injury baseline. Rarely, myositis ossificans and compartment syndrome may complicate acute soleus muscle injuries. Risk factors: These include: ● Age ● Deconditioned/unstretched muscles: ♥ The cold and unstretched muscles that recreational athletes often use to compete with are very likely to rupture when challenged compared with conditioned and stretched muscles ● Previous injury: ♥ The athlete with recurrent calf strains is likely to have healed with some degree of fibrotic scar tissue, which absorbs forces differently and is thus more likely to result in rupture when the muscle is re-challenged Clinical assessment Soleus strains tend to be less dramatic in clinical presentation and more subacute when compared to injuries of the gastrocnemius. The classic presentation is of a low grade injury resulting calf tightness, stiffness, and pain that worsens over a period of days to weeks. Swelling and disability are generally mild in comparison to gastrocnemius injuries. Differentiating a gastrocnemius muscle injury from a soleus muscle injury: Differentiating strains of the gastrocnemius muscle from the soleus muscle is important for both treatment and prognosis. 2 Gastrocnemius strains typically present with tenderness in the medial belly or the musculotendinous junction. In soleus strains the pain and tenderness is often lateral and more distal in the calf, in comparison to injuries of the gastrocnemius muscle. The origin of the gastrocnemius and soleus are anatomically distinct arising from above and below the knee respectively. This allows the examiner to isolate the activation of the muscles by varying the degree of knee flexion. With the knee in maximal flexion the soleus becomes the primary generator of force in plantar flexion. Conversely with the knee in full extension the gastrocnemius provides the greater contribution. This relationship allows for more accurate strength testing of the individual calf muscles and enables the clinician to better delineate which muscle has been injured. A similar approach is used to test pain and flexibility with passive ankle movements and stretching. In this case, the knee is again placed in maximal extension and then subsequently in flexion while the ankle is passively dorsiflexed to cause relative isolated stretch of the gastrocnemius and soleus respectively. So in summary: ● When the knee is fully flexed – active resistance to plantar flexion and passive stretching (by dorsiflexing the ankle) of the calf is primarily testing the soleus muscle. ● When the knee is fully extended – active resistance to plantar flexion and passive stretching (by dorsiflexing the ankle) of the calf is primarily testing the gastrocnemius muscle. It should be noted that concomitant tears of both the soleus and gastrocnemius are possible, though this is uncommon. This will complicate the clinical picture. Severity Muscle injuries are classically divided into 3 grades of severity. Grade I injury being an injured muscle without significant tearing or rupture, Grade II inquires being those that have partial tearing and grade III injuries being those that have a complete tear. Soleus muscle injuries most commonly are of grade I or II, rather than grade III Investigations Ultrasound Ultrasound is good initial imaging investigation to establish the nature and full extent of injury. MRI MRI is the best imaging modality for the diagnosis of soleus muscle/ tendon injuries. It is usually reserved for the assessment of elite sportspersons and/or or those with suspected severe injury. Management First aid: The basic principles of the initial management of any soft tissue injury apply These can be summarized as: RICE and No HARM. These protocols aim to minimize any further bleeding and edema into the muscle and are maintained over the first 48-72 hours, post injury. The aim is to reduce the bleeding, edema and further damage to the muscle. See separate Guidelines: Soft Tissue Injury. Analgesia: Simple oral analgesia is usually sufficient, unless the injury is severe, where titrated opioid may initially be required Options include: 2 For less severe pain use: ● Paracetamol 1gram orally 4 hourly prn (to a maximum dose of 4 gram per 24 hour period) And/or ● Ibuprofen 400mg orally 6 hourly prn For more severe pain use: ● Oxycodone immediate release 5 to 10 mg orally 4 to 6 hourly prn With ● Paracetamol 1gram orally 4 hourly prn (to a maximum dose of 4 gram per 24 hour period) And/or ● Ibuprofen 400 mg orally 6 hourly prn Following initial management: Rehabilitation: Recovery can often be quite a slow process, however it is usually somewhat quicker than is the case with gastrocnemius muscle injuries. Disposition For athletes and/or severe in juries there should be referral to: ● A physiotherapist ● A specialist in Sports Medicine. For Grade three tears, there should be referral to an Orthopaedic Surgeon. Appendix 1 Anatomy of the soleus muscle: The Soleus is a broad flat muscle situated immediately in front of the Gastrocnemius. It arises by tendinous fibers from the back of the head of the fibula, and from the upper third of the posterior surface of the body of the bone; from the popliteal line, and the middle third of the medial border of the tibia; some fibers also arise from a tendinous arch placed between the tibial and fibular origins of the muscle, in front of which the popliteal vessels and tibial nerve run. The fibers end in an aponeurosis which covers the posterior surface of the muscle, and, gradually becoming thicker and narrower, joins with the tendon of the Gastrocnemius, and forms with it the Achilles tendon. (Gray’s Anatomy 1918) References 1. The Acute Pain Management Manual NHMRC, 2011. 2. J. Bryan Dixon, Gastrocnemius versus soleus strain: how to differentiate and deal with calf muscle injuries. Curr Rev Musculoskeletal Med (2009) 2:74 - 77. Doi 10.1007/s12178-009-9045-8 Dr J. Hayes Acknowledgements: Hugh Burch May 2013 .