Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

Featured on Channel NewsAsia

Skeletal Muscle and Tendon

Key Points

  • Skeletal muscle has a complex organization of nerves, blood vessels, and connective tissue matrix that protects against injury and organizes individual cellular elements into functional contractile units of muscle.
  • Muscle fibers range a few millimeters to several centimeters in length. Fibers are arranged into larger units known as fascicles. Perimysium, a connective tissue sheath, surrounds fascicles. Whole muscles, made of numerous fasciculi, are surrounded by epimysium.
  • Tendon is juxtaposed between muscle and bone and is responsible for transmitting muscular forces to the skeletal system during limb locomotion.
  • The majority of skeletal muscle injuries that occur in sports are the result of indirect strain or direct blunt force trauma. Lacerations, ischemia, and infections are less common in athletics.
  • Indirect muscle strain injuries usually occur at the myotendinous junction during a stereotypical eccentric contraction. Certain muscles are more likely to sustain this type of injury (e.g., hamstrings during the rapid acceleration found in football, sprinting, and soccer).
  • Delayed muscle soreness (DMS) usually occurs at least 24 hours after exercise. Eccentric exercises, especially unfamiliar and repetitive ones, are more likely to predispose patients to DMS. Patients with DMS complain of pain, stiffness, and swelling in the muscles.
  • Direct trauma can occur at any point in the muscle. The quadriceps is the most common site of athletic muscle contusion, especially in football players. Under sufficient force, disruption of the muscle tissue and architecture can occur, often resulting in a hematoma.

Skeletal muscle accounts for nearly 45% of an average person’s body weight, making it the largest organ in the human body. Although it can be thought of as a single organ, skeletal muscle is highly compartmentalized into separate entities, each with its own unique role within a functional muscle.

Muscle has a complex organization of nerves, blood vessels, and connective tissue matrix that protects against injury and organizes individual cellular elements into functional contractile units of muscle. Skeletal muscle generates forces that result in bodily movement, steady posture, joint stabilization, and heat production through normal contractile functioning.

This chapter begins with a discussion of the cellular structure and architecture of muscle, including myofibrillar contractile proteins, and then proceeds to the larger subunits and, ultimately, to skeletal gross anatomy. A detailed knowledge of the muscle structure will aid in understanding the biomechanics and physiology of normal skeletal muscle described here as well.

Because muscles must exert their force on the human skeleton, the tendons that accomplish this task are discussed as well. Tendons are positioned between muscles and bones, so the tension generated by muscle contraction can be conveyed to the bone trigger locomotion.

The myotendinous junction is the transition point between muscle and tendon, and the osteotendinous junction (OTJ) is the point of tendon insertion into bone. Like the muscles they serve, tendons have an intricate cellular structure of collagen fibrils, elastin proteins, extracellular ground substance, and fibroblast cells.

Tendons also have a rich vascular supply and innervation, which are important for normal functioning. The biomechanical properties of tendons make them suitable for transmitting muscular forces to bone with minimal loss of energy or stretch.

Comments are closed.