MUSCLE ANATOMY
The muscle tendon unit comprises a
• proximal enthesis
• proximal tendon
• proximal myotendinous junction
• muscle belly
• distal myotendinous junction
• distal enthesis
Muscles may comprise a single muscle bundle, unipennate, or be bipennate or multipennate
may cross one or two joints
may comprise fast twitch, slow twitch or a combination of both types of muscle fibre
are arranged in compartments
Muscle injuries are
more common in the lower limb
more frequently involve muscles that cross to jointsÂ
Affect the proximal enthesis mainly in children
Affect the MTJ's in adults
Hamstring compartment
• Comprises three muscles, semimembranosus, semitendinosus and biceps femoris.
• The latter has two heads, long and short
• The long head arises in conjunction with semitendinosus as a conjoint tendon
• The short head arises from the lines aspera and lies more anterior and medial
• The distal biceps MTJ in complex, T shaped with the posterior element arising from the long head and the anterior component from the short head
Semimembranosus has a long, Nike tick shaped membranous proximal tendon and a prominent distal muscle belly
Semitendinosus comprises a prominent proximal muscle belly, arising from the conjoined tendon, and is more tendinous distally
Quadriceps compartmentÂ
• The rectus femoris component is the most frequently injured as it crosses two joints
• It arises from a direct head from the anterior inferior iliac spine and an indirect head from the superior margin of the acetabulum
• The indirect tendon becomes the proximal central tendon of the muscle which extends a considerable distance into the muscle belly
• The direct head forms the posterolateral part of the epimyseum
• The other components are the vastus medialis, lateralis and intermedius
Adductor Compartment
• Comprises from anterior to posterior: adductor Longus, Brevis and Magnus.
• Adductor longus is the most frequently injured.
There are three compartments in the calf: anterior peroneal and posterior
The posteriorly is frequently subdivided into deep and superficial