Muscle injuries occur from either direct or indirect trauma.
Predisposing factors include type of muscle architecture (i.e., pennate muscle, type II fast twitch muscle fibres, and muscle-tendon units that span 2 joints), previous injury, and inadequate warm-up before exercise.
Eccentric contraction (i.e., muscle contraction associated with forcible lengthening of the contracting muscle, such as when lowering a weight or pitching a ball) causes more frequent injury.
History and physical examination are key in diagnosis and grading of the injury as grade 1 (mild), 2 (moderate), or 3 (severe with complete rupture).
Conservative treatment is all that is required for most patients with grade 1 or 2 injuries.
Imaging studies are usually not necessary but can be obtained if grade 3 rupture is suspected, or to confirm or determine associated injuries.
Strain is an injury to the muscle or musculotendinous junction, whereas sprain is an injury to the ligament. Muscle contusion occurs when a muscle is subjected to a sudden, heavy compressive force, such as a direct blow to the muscle.
In strains, an excessive tensile force subjected onto the muscle leads to the overstraining of the myofibres and consequently to a rupture near the musculotendinous junction. Muscle strains typically concern the superficial muscles working across 2 joints, such as the rectus femoris, semitendinosus, and gastrocnemius muscles. Muscle strain usually occurs in eccentric exercise. In eccentric exercise the contracting muscle is forcibly lengthened; in concentric exercise it shortens. While concentric contractions initiate movements, eccentric contractions slow or stop them (e.g., when lowering a weight).
Staff Orthopaedic Surgeon
Department of Orthopaedics
VA Medical Center
SNS declares that he has no competing interests.
Department of Orthopaedic Surgery
Virginia Commonwealth University
VM is an editorial board member, European Journal of Orthopaedic Surgery & Traumatology.
Spinal Clinical Research Fellow
Queens Medical Centre
SRM declares that he has no competing interests.
Dr Senthil N. Sambandam, Dr Varatharaj Mounasamy, and Dr Sakthivel Rajaram Manoharan would like to gratefully acknowledge Dr Issada Thongtrangan, a previous contributor to this monograph. IT declares that he has no competing interests.
Department of Orthopaedics
University of Virginia
QC declares that he has no competing interests.
Professor of Trauma and Orthopaedic Surgery
University Hospital of North Staffordshire
Keele University School of Medicine
Stoke on Trent
NM is an author of a study referenced in this monograph.
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