Muscle injury is a broad term that encompasses many conditions and is common among elite and amateur athletes as well as the general population .
Skeletal muscle injuries account for a significant portion of all trauma in sports medicine, accounting for 10% to 55% of all persistent injuries. The muscles and muscle groups more commonly affected are the rectus femoris hamstrings and the medial head of the gastrocnemius.  They should be treated Take the necessary precautions, as failure of treatment may delay an athlete’s return to competition by weeks or even months and increase the risk of re-injury.
Figure 1: Complete rupture of the distal rectus femoris tendon junction with a gap of approximately 3 cm in the craniocaudal defect.
Several types of muscle damage can occur: lacerations, contusions, degenerative diseases (such as muscular dystrophy ), and strains.
- A laceration occurs when a muscle is cut by an external object, which usually occurs in traumatic accidents such as road traffic or industrial accidents.
- A contusion occurs when a muscle is stressed, usually in contact sports, such as in football when the knee collides with the thigh when two players tackle the ball.
- A strain occurs when a muscle fiber cannot withstand the excessive tension placed on it, and is therefore usually associated with eccentric muscle action. Strains most often occur in muscles that span two joints, such as the hamstring gastrocnemius during rapid acceleration deceleration by placing the muscles in a stretched position at both joints and contracting them forcefully 
Types of Skeletal Muscle Injuries
Despite the clinical importance of muscle injuries, the literature does not show great consensus when it comes to categorizing muscle injuries. However, the most differentiating factor is the trauma mechanism. Therefore, muscle injuries can be broadly classified as traumatic (acute) or overuse (chronic) injuries.
Acute injuries are often the result of a single traumatic event, causing macroscopic trauma to the muscle. There is a clear link between the cause and the apparent symptoms. They occur mostly in contact sports such as football and basketball because of their dynamic and high-impact nature Nature .
Overuse chronic or exercise-induced injuries are subtler and usually last longer. They are caused by repetitive microtrauma to the muscles. Diagnosis is more challenging because the link between the cause of the injury and the symptoms is less obvious . The video below gives Talk briefly about these chronic injuries.
Muscle Injury Classification
Traditional Classification Systems
Muscle injuries are common injuries in sports. Historically, a three-level grading system based on clinical symptoms has been used to guide the prognosis of muscle strains. A grading system is useful because it provides an indication of the severity or extent of the injury. With advances in imaging technology For example MRI and ultrasonography now have the benefit of combining clinical and radiological findings, which has led to a ‘new’ muscle injury grading and classification system 
modern muscle injury classification system
- Munich Consensus System
- International clinical and basic science experts have developed a comprehensive muscle injury classification and grading system. 
- Highlights of the Munich Consensus System :
- Classification distinguishes between direct (bruises and tears) and indirect muscle injuries
- Indirect muscle injuries are further classified as functional or structural
- Further subdivided by type of injury and by diagnostic group (e.g., fatigue-induced muscle impairment; delayed onset muscle soreness (DOMS); or muscle or spine-related neuromuscular impairment) or severity (mild, partial, moderate, complete or tear off).
- Muscle injury is addressed in a comprehensive manner, including descriptors such as acute overuse direct and indirect injury.
Read the full article here: Terminology and classification of muscle injuries in sports: Munich consensus statement 
- British athletics system
- Pollock et al.  devised a classification of non-contact muscle injuries
- The system grades the injury on a scale of 0 – 4 based on clinical and MRI features
- The injury is then further subdivided to reflect the major anatomical structures involved:
- a = myofascia; b = usually within the muscle at the tendon junction; c = intratendon tear
- Grade 0 injury – MRI negative and described as “focal neuromuscular injury” or muscle injury consistent with DOMS
- If a neural component is suspected – N can be used as an additional discriminator
- Grades 1-3 refer to small to moderate or large tears of muscle tissue respectively (depending on the degree of edema and tissue destruction and the tissues involved)
- Grade 4 is a complete tear of the muscle or tendon
- BAMIC (British Athletics Muscle Injury Classification) provides a framework for clinical reasoning and rehabilitation decision-making 
- Read the full article here: UK Athletics Classification of Muscle Injuries: A New Grading System
- Chan System
-  proposed a 3-tier anatomical classification system – this is primarily an imaging-based classification system
- The anatomical location of the injury is: proximal tendon junction muscle or distal tendon junction
- Lesions are then subdivided as proximal, intermediate, or distal
- Thereafter, injury is defined by the primary tissue involved (eg, intramuscular myofascial perifascial tendon or combination)
- Read the article here: Acute muscle strain: a proposed new classification system 
- Barcelona System
- The medical department of FC Barcelona and international counterparts proposed a muscle injury classification and grading system based on 4 layers/layers
- MLG-R System
- M – Mechanism of injury
- L – Location of injury
- G – Grading of severity
- R – Number of muscle re-injuries
- From clinical history – mechanism of injury (direct (D) or indirect (I))
- The indirect injury was further determined to be sprinting or stretching related
- The second and third identifiers are MRI variables – anatomical location and extent of injury
- The fourth identifier is related to reinjury status
- Read the study here: Muscle Injuries in Sports: A New Evidence-Based and Expert Consensus-Based Classification for Clinical Application 
- Grading Based on Connective Tissue Injury
- Prakash et al.  proposed an MRI grading system to assess the extent of injury and the integrity of the involved connective tissue structures
- Grade 0 – edema or fluid adjacent to intact connective tissue (tendon/aponeurosis/advention), no myofibril detachment
- Grade 1 – detachment of myofibrils without connective tissue changes
- Grade 2 – Detachment of myofibrils with increased signal delamination or defect of adjacent connective tissue but no retraction
- Grade 3 – Detachment of myofibrils with contraction of adjacent connective tissue, indicating failure
- Prakash et al.  proposed an MRI grading system to assess the extent of injury and the integrity of the involved connective tissue structures
Muscle Injury Types
A muscle or tendon strain is equivalent to a ligament sprain. This is a contraction-induced injury in which muscle fibers tear due to extensive mechanical stress. This is mainly due to strong eccentric contractions (see EIMD) or overstretching of the muscles. Muscles are likely to tear during sudden acceleration or deceleration.  Therefore, it is typical of non-contact sports with dynamic properties, such as sprint jumping. 
The Munich Consensus Statement on the Terminology and Classification of Muscle Injuries in Sports classifies strain severity as: :
Grade I (Mild)
- Only a few fibers in the muscle are involved.
- There is no loss of strength and there is a full range of active and passive motion.
- Localised pain
- Pain and tenderness are usually delayed until the next day.
Grade II (Moderate)
- Involves massive tearing of muscle fibers
- Acute and significant pain with swelling
- Pain is reproduced on muscle contraction
- Strength is reduced
- Movement is limited by pain
Grade III (Severe)
- The muscle is completely torn/broken. This means that either the tendon separates from the muscle belly, or the muscle belly is actually torn in two.
- Severe swelling and pain and complete loss of function are characteristic of this type of strain.
- This is most common at the tendon junction.
Many factors predispose athletes to muscle strains:
- Inadequate Warm-up
- Insufficient Joint Range of Motion
- Excessive Muscle Tightness
- Fatigue/overuse/inadequate recovery
- Muscle Imbalance
- Previous Injury
- Faulty Technique / Biomechanics
- Spinal Dysfunction
Common Strain Injuries
- Hamstring Strain
- Quadriceps Muscle Contusion
- Calf Strain
- Groin Strain
- Rotator Cuff Tears
- Rupture Long Head Biceps
- Achilles Rupture
Muscle contusions are often the result of direct blows from opposing players or contact with equipment in collision sports such as soccer, rugby, and hockey. The blow causes localized muscle damage with bleeding.  A bruise or contusion is a hematoma of tissue in which Capillaries and sometimes venules are damaged by trauma, allowing blood to bleed or ooze into the surrounding interstitial tissue. A bruise that does not turn white under pressure may involve capillaries in the subcutaneous tissue of the skin at the muscle or bone level. as a type of hematoma Bruises are caused by bleeding within the interstitial tissue that does not penetrate the skin, usually from blunt trauma that inflicts damage through physical compression and deceleration forces. Trauma sufficient to cause bruising can occur in a variety of sports. bruises Usually painful, but small bruises are usually not dangerous. Sometimes bruising can be severe, leading to other, more life-threatening forms of hematoma, such as those associated with serious injuries including broken bones and more severe internal bleeding. the likelihood and severity of Bruising depends on many factors, including the type and health of the affected tissue.
Muscle cramps are sudden involuntary muscle contractions or excessive shortening. While cramps are usually temporary and harmless, they can cause mild to excruciating pain and paralyzing immobility in the affected muscle. Onset is usually sudden and resolves on its own over time seconds or hours. Cramps can occur in skeletal or smooth muscle.
Even among elite athletes, muscle cramps during exercise are common. The most commonly cramped muscles are the calves, thighs, and arches. These cramps are associated with strenuous physical activity and can be very painful; however, they can occur even with inactivity/relaxation. About 40% of people who experience bone spasticity may suffer from extreme muscle pain and may not be able to use the entire limb including the locked muscle group. It may take up to 7 days for the muscles to return to a pain-free state.
According to Brukner and Kahn , disturbances at different levels of the central and peripheral nervous system as well as of the skeletal muscles are involved in the mechanism of cramps and can explain the various conditions under which cramps occur. Other popular theories about the cause of cramps include Dehydration Low potassium or sodium levels Inadequate carbohydrate intake or excessive muscle tightness, but these hypotheses seem unpopular because of the overwhelming evidence supporting the “nerve excitability” hypothesis. 
Muscle soreness after exercise is often referred to as delayed onset muscle soreness (DOMS). DOMS is common in individuals who engage in vigorous and unaccustomed exercise and physical activity. It is classified as a grade 1 muscle strain and is characterized by localized tenderness and pain. It usually peaks within 24 to 72 hours after a bout of exercise, but eventually wears off after 5 to 7 days.  Soreness is accompanied by prolonged loss of strength, reduced range of motion, and elevated levels of creatine kinase in the blood. These are considered indirect Muscle damage indicators and biopsy analysis document damage to contractile elements. The exact cause of the soreness response is unknown, but is thought to be related to the inflammatory response to injury. [twenty one]
Perceived pain during exercise is thought to be caused by a combination of factors including acid ions, proteins and hormones. While it’s widely believed that lactic acid is responsible for this pain, evidence suggests it’s not the only factor. [twenty one]
The healing process of injured skeletal muscle includes overlapping stages of degenerative inflammation, regeneration and fibrosis. Efficient regeneration of injured muscle is thought to compete with fibrotic healing, and excessive fibrosis is thought to impede regeneration. this balance Primarily depends on the cells and factors present in the degenerative and inflammatory phases of healing . Regardless of the underlying cause, the processes occurring in an injured muscle tend to follow the same pattern. However, functional recovery varies by one type of injury. Two phases can be distinguished during the restoration process .
Start with the actual trauma that caused the muscle fibers to tear. Immediate necrosis of muscle fibers occurs due to deterioration of the sarcoplasm, a process that is arrested within hours of trauma by the formation of a temporary membrane by lysosomal vesicles . The inflammatory process occurs in Reaction to a torn blood vessel. Specialized cells start to remove the necrotic part of the fibers .
Repair and Remodeling Phase
The actual repair of the injured muscle happens. Myofibers start to regenerate from satellite cells (= undifferentiated reserve cells) and connective tissue scars form in the spaces between the torn muscle fibers. This scar tissue is most vulnerable during the first 10 days after trauma Affected muscle points. After 10 days, however, the eventual re-rupture affects adjacent muscle tissue rather than the scar tissue itself, although full recovery (reaching pre-injury strength) may take a relatively longer time. Vascularization of the injured site is a prerequisite for treatment Recovery from muscle damage. New capillaries originate from remaining injured blood vessels and find their way to the center of the injured area. Early mobilization plays a very important role as it stimulates the angiogenesis process. Like wise intramuscular nerves regenerate Re-establish neuromuscular contact .
Post-traumatic skeletal muscle has the capacity to regenerate and repair complex and well-coordinated responses. This process requires the presence of distinct cell populations, the up- and down-regulation of various gene expressions and the involvement of multiple growth factors. regeneration Strategies based on the combination of stem cell (satellite cell) growth factors and biological scaffolds have shown promising results in animal models. Better understanding of cellular and molecular pathways and better definition of interactions (cell-cell and cell matrix) are essential for efficient muscle regeneration and should facilitate the development of new therapeutics in humans .
Figure 3: Biological scaffolds composed of extracellular matrix.
For both acute and chronic injuries, a thorough subjective examination is the primary method for identifying muscle damage. Special attention should be paid to the history of trauma. Clinical examination and muscle function tests and patient recall of what What happened was mostly enough to make a correct diagnosis. In some cases, additional tests (MRI X-ray ultrasound CT scan) may be needed to determine the extent of the injury or to identify possible additional injuries.
The video below gives a good look at the diagnostic procedure for muscle injuries
Acute Skeletal Muscle Injuries
Over the past few years, the POLICE Principle (an updated version of the RICE Principle) has generally been considered the best way to minimize swelling and relieve pain within the first 24 to 48 hours. Although the different components of the RICE principles all show their role in Experimental studies The use of the holistic concept has yet to be confirmed in randomized clinical trials . These approaches focus on acute management and do not really provide any information on the subacute and chronic phases of soft tissue healing. More recent Dubois and Escoulier (2019) Two new acronyms are proposed to optimize soft tissue recovery: PEACE and LOVE.  These two acronyms (PEACE and LOVE) cover the full spectrum of soft tissue injury management from immediate care to follow-up management. It also highlights the importance of patient education and problem solving Involves psychosocial factors that contribute to recovery. It also highlights the potentially harmful effects of recovery with anti-inflammatory drugs.  Learn more about the principles of peace and love in the management of soft tissue injuries here.
Evidence for early mobilisation
First aid treatment must be tailored to the severity and extent of the injury. Immobilization for a short period of time after trauma prevents excessive formation of scar tissue (which can have a detrimental effect on the mobility and strength of the healing muscle) and prevents re-rupture By allowing the scar tissue to gain sufficient strength to withstand contraction forces. Immobilization should not be continued after the acute phase (first few days) to avoid negative effects such as muscle atrophy, delayed strength recovery, and excessive connective tissue formation. Muscle .
Early mobilization can begin after a few days if the acute phase has passed without further complications and recovery appears to be progressing. Mobilization induces significant histological changes compared to fixation, such as better increased vascularization in the injured area Regeneration and more parallel orientation of muscle fibers. It also has the added benefit that the muscle will gain its original strength more quickly .
Aggressive treatment requires a gradual build-up from isometric to isotonic exercises. Isokinetic training should only be initiated when these exercises can be performed without pain.
Because muscle injuries usually heal well with conservative management, surgical intervention is considered only in very specific indications :
- Large intramuscular haematoma
- complete muscle tear (third degree strain)
- Localized strain if more than half of the muscle belly is affected (Grade 2)
- Scar adhesions causing persistent pain and limited extension (>4-6 months)
Chronic Skeletal Muscle Injuries
In almost every sporting activity, overuse sports injuries outnumber acute transient injuries. Because they do not immediately incapacitate a person, they attract less medical attention than acute injuries. Their frequency is almost always underestimated in sports injury investigations. Various factors make the treatment of overuse sports injuries difficult, such as the insidious start of an injury that is already established and more difficult to successfully manage by the time the athlete actually arrives for treatment. Injuries occur when the cumulative force exceeds the capacity of the tissue Withstand such forces—whether due to isolated macrotraumatic events or repeated microtraumatic events. Often specific biomechanical or physiological factors predispose athletes to injury. Physiotherapists should properly identify and assist athletes to correct these conditions to Treatment To prevent and possibly reverse adverse effects. As always, prevention is always the best cure, but failing that, the secondary thing is proper and successful recovery. 
Clinical Bottom Line
Treatment for muscle injuries usually has good results. Physical therapists must ensure that muscles are rehabilitated in all functional aspects before resuming daily activities or demanding physical activity. Management of soft tissue injuries, whether hamstring strains or ankle sprains  The focus should not be on short-term damage control. Clinicians should also focus on long-term outcomes and focus on treating the injured rather than just the injured. 
- ↑ Radiopedia Muscle Injuries Available from:https://radiopaedia.org/articles/muscle-injury (accessed 27.5.2021)
- ↑ Maffulli N, Del Buono A, Oliva F, Via AG, Frizziero A, Barazzuol M, Brancaccio P, Freschi M, Galletti S, Lisitano G, Melegati G. Muscle injuries: a brief guide to classification and management. Translational Medicine@ UniSa. 2015 May;12:14.Available:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4592039/ (accessed 27.5.2021)
- ↑ Jump up to:3.0 3.1 Laumonier T, Menetrey J. Muscle injuries and strategies for improving their repair. Journal of experimental orthopaedics. 2016 Dec;3(1) Available from:https://jeo-esska.springeropen.com/articles/10.1186/s40634-016-0051-7#Abs1:(1-9.Accessed 11.4.2021)
- ↑ Musculoskeletalkey Pathophysiology of Skeletal Muscle Injury Available from: https://musculoskeletalkey.com/pathophysiology-of-skeletal-muscle-injuries/ (accessed 9.3.2021)
- ↑ Jump up to:5.0 5.1 Best TM. Soft-tissue injuries and muscle tears. Clin Sports Med. Jul 1997; 16(3):419-34
- ↑ Beiner J, Jokl P. Muscle Contusion Injuries: Current Treatment Options. J Am Acad Orthop Surg July 2001; 9:227-237
- ↑ Universal Hospitals Common muscle and sports injuries Available from: https://www.youtube.com/watch?v=EkdllXH5AME (last accessed 7.6.2019)
- ↑ Hamilton B, Pollock N, Reurink G, Vos RJ, Purdam C, Thorborg K. Muscle Injury Classification and Grading Systems. In Prevention and Rehabilitation of Hamstring Injuries 2020 (pp. 189-198). Springer, Cham.
- ↑ Jump up to:9.0 9.1 9.2 9.3 Mueller-Wohlfahrt HW, Haensel L, Mithoefer K, Ekstrand J, English B, McNally S, Orchard J, van Dijk CN, Kerkhoffs GM, Schamasch P, Blottner D. Terminology and classification of muscle injuries in sport: the Munich consensus statement. British journal of sports medicine. 2013 Apr 1;47(6):342-50.
- ↑ Jump up to:10.0 10.1 Pollock N, James SL, Lee JC, Chakraverty R. British athletics muscle injury classification: a new grading system. British journal of sports medicine. 2014 Sep 1;48(18):1347-51.
- ↑ Macdonald B, McAleer S, Kelly S, Chakraverty R, Johnston M, Pollock N. Hamstring rehabilitation in elite track and field athletes: applying the British athletics muscle injury classification in clinical practice. British journal of sports medicine. 2019 Dec 1;53(23):1464-73.
- ↑ Jump up to:12.0 12.1 Chan O, Del Buono A, Best TM, Maffulli N. Acute muscle strain injuries: a proposed new classification system. Knee Surgery, Sports Traumatology, Arthroscopy. 2012 Nov;20(11):2356-62.
- ↑ Jump up to:13.0 13.1 13.2 Valle X, Alentorn-Geli E, Tol JL, Hamilton B, Garrett WE, Pruna R, Til L, Gutierrez JA, Alomar X, Balius R, Malliaropoulos N. Muscle injuries in sports: a new evidence-informed and expert consensus-based classification with clinical application. Sports medicine. 2017 Jul;47(7):1241-53.
- ↑ Prakash A, Entwisle T, Schneider M, Brukner P, Connell D. Connective tissue injury in calf muscle tears and return to play: MRI correlation. British journal of sports medicine. 2018 Jul 1;52(14):929-33.
- ↑ Jump up to:15.00 15.01 15.02 15.03 15.04 15.05 15.06 15.07 15.08 15.09 15.10 15.11 Brukner P. Brukner & Khan’s Clinical Sports Medicine. McGraw-Hill Education; 2017.
- ↑ Garrett WE. Muscle strain injuries. Am J Sports Med. 1996; 24:S2-88
- ↑ Jump up to:17.0 17.1 17.2 17.3 17.4 Tero AH Järvinen, Teppo LN Järvinen, Minna Kääriäinen, Hannu Kalimo, Markku Järvinen. Basic Science Update: Muscle Treatment. Am J Sports;May;33:745-­‐764
- ↑ Jump up to:18.0 18.1 Järvinen M, Tero AH. Muscle strain injuries. Rheumatology. 2010(2); 12: 155-161
- ↑ Jump up to:19.0 19.1 Kneeland JP. MR imaging of muscle and tendon injury. Eur J Radiol. Nov 1997; 25(3):198-208
- ↑ Ranchordas MK, Rogerson D, Soltani H, Costello JT. Antioxidants for preventing and reducing muscle soreness after exercise. Cochrane Database of Systematic Reviews. 2017(12).
- ↑ Jump up to:21.0 21.1 Miles MP, Clarkson PM. Exercise-induced muscle pain, soreness, and cramps. The Journal of sports medicine and physical fitness. 1994 Sep;34(3):203-16.
- ↑ Martins L, Gallo CC, Honda TS, Alves PT, Stilhano RS, Rosa DS, Koh TJ, Han SW. Skeletal muscle healing by M1-like macrophages produced by transient expression of exogenous GM-CSF. Stem cell research & therapy. 2020 Dec;11(1):1-2.Available from:https://stemcellres.biomedcentral.com/articles/10.1186/s13287-020-01992-1 (accessed 11.4.2021)
- ↑ Kalimo H, Rantanen J, Järvinen M. Muscle injuries in sports. Baillieres Clin Orthop. 1997;2: 1-24
- ↑ Huard J, Li Y, Fu FH. Muscle injuries and repair: Current trends in research. J Bone Joint Surg AM. 2002; 84:822-832
- ↑ Kasemkijwattana C, Menetrey J, Somogyl G, et al. Development of approaches to improve the healing following muscle contusion. Cell Transplant. Nov-Dec 1998; 7(6):585-98
- ↑ Jump up to:26.0 26.1 Järvinen M, Sorvari T. A histochemical study of the effect of mobilization and immobilization on the metabolism of healing muscle injury. In: Landry F, ed. Sports Medicine. Miami, Fla: Symposia Specialists, Orban WAR; 1978:177-181
- ↑ Nozaki M, Li Y, Zhu J, et al. Improved muscle healing after contusion injury by the inhibitory effect of suramin on myostatin, a negative regulator of muscle growth. Am J Sports Med Dec 2008; 36(12): 2354-62
- ↑ Chris Beaulieu Muscle injuries and interventions. Available from: https://www.youtube.com/watch?v=MPqjFEhEBB4&app=desktop (last accessed 7.6.2019)
- ↑ Jump up to:29.0 29.1 29.2 29.3 Dubois B, Esculier J. Soft-tissue injuries simply need PEACE and LOVE. British Journal of Sports Medicine 2020;54:72-73.
- ↑ Järvinen M, Lehto MUK. The effect of early mobilization and immobilization on the healing process following muscle injuries. Sports Med. 1993; 15:78-89
- ↑ Elmer G. Pinzon, MD, MPH, DABIPP and Mick Larrabee, PT, MS, SCS, EMT, CSCS Chronic Overuse Sports Injuries Available from: https://www.practicalpainmanagement.com/pain/acute/sports-overuse/chronic-overuse-sports-injuries (last accessed 7.6.2019)