Ch. 12 Appendicular Muscles::Question

Proximal: Inferior ramus and body of pubis; Distal: Upper medial surface of tibia

Femoral nerve (L2-L4) or obturator nerve (L2-L4)

The popliteus flexes the knee and causes slight medial rotation to unlock the knee joint.

They work synergistically in the medial rotation of the humerus.

The hamstring muscles attach to the ischial tuberosity and extend the thigh plus flex the leg.

The flexor carpi radialis can abduct (radially deviate) the hand.

Adducts thigh; adductor part of muscle flexes thigh; hamstring part of muscle extends and laterally rotates thigh

Abducts thigh; medially rotates thigh

The Gracilis muscle assists in adducting the thigh and flexing the leg at the knee.

The quadriceps femoris is composed of the vastus lateralis, vastus medialis, rectus femoris, and vastus intermedius.

The opponens pollicis is responsible for thumb opposition.

The thenar group muscles include:

1. Flexor pollicis brevis - Flexes the thumb.
2. Abductor pollicis brevis - Abducts the thumb.
3. Opponens pollicis - Assists in the opposition of the thumb.

The hypothenar group muscles include:

1. Flexor digiti minimi brevis - Flexes the little finger.
2. Abductor digiti minimi - Abducts the little finger.
3. Opponens digiti minimi - Assists in the opposition of the little finger.

The mnemonic is PAD-DAB:

• PAD: Palmar interossei ADduct the fingers.
• DAB: Dorsal interossei ABduct the fingers.

The main action is to dorsiflex the foot and extend the toes.

The anconeus does not flex the forearm.

Flexes MP joints and extends PIP and DIP joints of toes 2-5.

Abducts the toes.

Adducts the toes.

The flexor digiti minimi brevis flexes the MP joint of toe 5 and is innervated by the lateral plantar nerve (S2-S3).

Proximal: Calcaneus and inferior extensor retinaculum; Distal: Middle phalanges of toes 2-4.

Adducts the great toe (1).

The muscles responsible for dorsiflexion of the foot include:

• Tibialis anterior
• Extensor digitorum longus
• Extensor hallucis longus
• Fibularis tertius

The muscles involved in plantar flexion of the foot include:

• Gastrocnemius
• Soleus
• Flexor digitorum longus
• Flexor hallucis longus
• Tibialis posterior
• Fibularis longus
• Fibularis brevis
• Plantaris

The muscles in the lateral compartment of the leg are primarily responsible for eversion of the foot. The main muscles include:

• Fibularis longus
• Fibularis brevis
• Fibularis tertius (slight effect)

The intrinsic muscles of the foot that extend the toes include:

• Extensor digitorum brevis
• Extensor hallucis brevis

The hamstring muscles are responsible for the following actions:

1. Flexion of the knee joint
2. Extension of the hip joint
3. Medial and lateral rotation of the leg (depending on the position of the knee)

The muscles responsible for the extension of the knee joint/leg include:

• Quadriceps femoris (comprising four muscles: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius)

The pectoralis major flexes the arm, while the latissimus dorsi extends it. Both muscles also adduct and medially rotate the arm.

The rotator cuff muscles, which include the subscapularis, supraspinatus, infraspinatus, and teres minor, provide strength and stability to the glenohumeral joint and assist in moving the humerus.

The biceps brachii is responsible for flexing and supinating the forearm, while the triceps brachii is responsible for extending the forearm.

The flexor retinaculum and extensor retinaculum are strong fibrous bands that hold the tendon sheaths of the forearm muscles close to the skeletal elements of the wrist, facilitating coordinated movement.

The intrinsic muscles of the hand are divided into three groups: (1) the thenar group, (2) the hypothenar group, and (3) the midpalmar group located between the thenar and hypothenar groups.

The gluteus maximus extends and laterally rotates the thigh, while the gluteus medius and minimus are powerful abductors of the thigh.

The quadriceps femoris is primarily responsible for extending the leg at the knee joint.

The anterior compartment muscles of the leg dorsiflex the foot and extend the toes, with one muscle also inverting the foot.

The dorsal muscles of the foot extend the toes, while the plantar muscles (which consist of four layers) flex, extend, abduct, and/or adduct the toes.

The lumbrical muscles flex the MP joints and extend the PIP and DIP joints of fingers 2-5.

Flexes thigh, extends leg

Adducts thigh; flexes thigh

The dorsal interossei muscles primarily abduct fingers 2-5.

The muscles responsible for the retraction of the scapula are the Trapezius and Rhomboids.

The main categories of muscles in the appendicular system are:

1. Muscles of the Pectoral Girdle and Upper Limb

   • Muscles That Move the Pectoral Girdle
   • Muscles That Move the Glenohumeral Joint/Arm
   • Arm and Forearm Muscles That Move the Elbow Joint/Forearm
   • Forearm Muscles That Move the Wrist Joint, Hand, and Fingers
   • Intrinsic Muscles of the Hand

2. Muscles of the Pelvic Girdle and Lower Limb

   • Muscles That Move the Hip Joint/Thigh
   • Thigh Muscles That Move the Knee Joint/Leg
   • Leg Muscles
   • Intrinsic Muscles of the Foot

The major movements of the pectoral girdle and upper limb include:

1. Elevation - Muscles: Trapezius, Levator scapulae
2. Depression - Muscles: Trapezius, Pectoralis minor
3. Protraction - Muscles: Serratus anterior, Pectoralis minor
4. Retraction - Muscles: Trapezius, Rhomboids
5. Rotation - Muscles: Serratus anterior, Trapezius
6. Flexion - Muscles: Pectoralis major, Deltoid (anterior fibers)
7. Extension - Muscles: Latissimus dorsi, Deltoid (posterior fibers)
8. Abduction - Muscles: Deltoid (middle fibers), Supraspinatus
9. Adduction - Muscles: Pectoralis major, Latissimus dorsi

The muscles that move the scapula include:

The muscles of the glenohumeral joint include:

The compartments of the arm include:

1. Anterior compartment:

   • Biceps brachii
   • Brachialis
   • Coracobrachialis

2. Posterior compartment:

   • Triceps brachii
   • Anconeus

The muscles that move the wrist joint, fingers, and thumb include:

1. If a muscle crosses over or spans a joint, it must move that joint.
2. If a muscle doesn't cross over or span a joint, it cannot move that joint.

The anterior thoracic muscles include:

• Pectoralis Minor: Helps depress and protract the scapula.
• Serratus Anterior: Agonist in scapula protraction, stabilizes the scapula against the rib cage, and is a powerful superior rotator of the scapula.
• Subclavius: Stabilizes and depresses the clavicle.

The serratus anterior muscle is the agonist in scapula protraction, stabilizes the scapula against the rib cage, and acts as a powerful superior rotator of the scapula, moving the glenoid cavity superiorly during upper limb abduction.

The pectoralis minor muscle helps depress and protract the scapula. It contracts when the shoulders are hunched forward, contributing to poor shoulder posture.

The key muscles involved in the protraction of the scapula are the Pectoralis minor and Serratus anterior.

The muscles involved in the elevation of the scapula include the Rhomboid major, Rhomboid minor, Levator scapulae, and the superior part of the Trapezius.

The muscles that act as depressors of the scapula are the inferior part of the Trapezius and Pectoralis minor.

The superior rotators of the scapula are the Serratus anterior and the superior part of the Trapezius.

The inferior rotators of the scapula include the Rhomboid major, Rhomboid minor, and Levator scapulae.

The primary action of the levator scapulae muscle is to elevate the scapula and it can also inferiorly rotate the scapula.

The trapezius muscle can elevate, depress, retract, or rotate the scapula, depending on which fibers are contracting. The superior fibers elevate and superiorly rotate the scapula, the middle fibers retract it, and the inferior fibers depress it.

The rhomboid minor and rhomboid major help to elevate, retract (adduct), and inferiorly rotate the scapula.

The serratus anterior muscle primarily acts as a protractor of the scapula. When paralyzed, it leads to a condition known as winged scapula, where the scapula on the affected side protrudes posteriorly, resembling a bird's wing, especially when the patient pushes against a wall with both arms.

The long thoracic nerve innervates the serratus anterior muscle. Damage to this nerve can occur during surgical procedures such as radical mastectomy, leading to paralysis of the muscle.

In a patient with winged scapula, the scapula on the injured side protrudes posteriorly, while the scapula on the unaffected side remains in the expected anatomical position, close to the thoracic wall.

The main muscles depicted include:

The Pectoralis minor muscle protracts and depresses the scapula.

The Serratus anterior muscle is the agonist in scapula protraction and also superiorly rotates the scapula.

The Subclavius muscle stabilizes and depresses the clavicle.

The Trapezius muscle has three sets of actions: Superior fibers elevate and superiorly rotate the scapula, middle fibers retract the scapula, and inferior fibers depress the scapula.

The Latissimus dorsi muscle is the agonist for arm extension and also adducts and medially rotates the arm.

The Pectoralis major muscle is the agonist for arm flexion and also adducts and medially rotates the arm.

The Deltoid muscle is the agonist for arm abduction and has different fibers that flex, abduct, and extend the arm.

The Coracobrachialis muscle works as a synergist to the Pectoralis major in flexing and adducting the arm.

The rotator cuff muscles are crucial for stabilizing the glenohumeral joint and facilitating arm movement.

The rotator cuff muscles (subscapularis, supraspinatus, infraspinatus, and teres minor) provide strength and stability to the glenohumeral joint by securing the head of the humerus in the glenoid cavity, allowing for a wide range of motion while maintaining joint integrity.

The supraspinatus muscle tends to suffer the most injuries due to its location and function. It is often subjected to repetitive overhead motions, which can lead to wear and tear, especially in activities like pitching or swimming.

Rotator cuff injuries are commonly caused by extensive and repetitive use of the rotator cuff muscles, leading to tearing of muscle fibers or rupture of tendon attachments. The supraspinatus muscle is most frequently injured due to its tendon becoming impinged beneath the acromion during shoulder movements.

Treatment for severe rotator cuff injuries typically includes:

1. Use of NSAIDs (non-steroidal anti-inflammatory drugs)
2. Corticosteroid shots
3. Physical therapy
4. Surgical repair may be required for severe cases, although some individuals may not regain full athletic use of the shoulder post-surgery.

The latissimus dorsi muscle acts as an agonist of arm extension and also adducts and medially rotates the arm, often referred to as the 'swimmer's muscle'.

The primary action of the pectoralis major muscle is to flex the arm, and it also adducts and medially rotates the arm.

The supraspinatus muscle is primarily responsible for arm abduction.

The deltoid muscle is innervated by the axillary nerve (C5-C6).

The proximal attachment of the teres major muscle is the inferior lateral border and inferior angle of the scapula, while its distal attachment is the lesser tubercle and intertubercular groove of the humerus.

The infraspinatus muscle adducts and laterally rotates the arm.

The coracobrachialis muscle adducts and flexes the arm.

The primary muscles responsible for flexing the elbow joint are the Biceps brachii and Brachialis.

The muscles of the arm are organized into compartments: the anterior compartment contains elbow flexors (like Biceps brachii and Brachialis), while the posterior compartment contains elbow extensors.

The primary action of the levator scapulae is to elevate the scapula.

The Biceps brachii is located in the upper arm and consists of two heads:

• Long head: runs along the upper arm and attaches to the shoulder.
• Short head: originates from the coracoid process of the scapula. Both heads converge to form a single muscle belly that inserts at the radial tuberosity.

The Coracobrachialis muscle assists in:

• Flexion of the arm at the shoulder joint.
• Adduction of the arm, bringing it closer to the body.

The Triceps brachii is primarily responsible for:

• Extension of the elbow joint, allowing for straightening of the arm.

The Biceps brachii and Brachialis muscles work together to flex the elbow joint:

• Biceps brachii: Also supinates the forearm.
• Brachialis: Acts as a primary flexor of the elbow, regardless of forearm position.

The biceps brachii contributes to shoulder movement by helping to flex the humerus, although this action is considered weak compared to its primary function of flexing the forearm.

The triceps brachii is the prime extensor of the forearm, and its action is antagonistic to that of the biceps brachii.

Only the long head of the triceps brachii crosses the glenohumeral joint, where it helps extend the humerus.

The anconeus is a weak elbow extensor that crosses the posterolateral region of the elbow.

Both the pronator teres and pronator quadratus rotate the radius across the anterior surface of the ulna to pronate the forearm.

The supinator works synergistically with the biceps brachii to supinate the forearm.

The Biceps brachii flexes the forearm, acts as a powerful supinator of the forearm, and weakly flexes the arm.

The Brachialis is the primary flexor of the forearm.

The Triceps brachii is innervated by the radial nerve (C5-C7 fibers).

The Pronator quadratus pronates the forearm.

The Biceps brachii and Supinator are the primary muscles involved in forearm supination.

The forearm muscles are partitioned into an anterior (flexor) compartment and a posterior (extensor) compartment.

Most anterior compartment muscles attach to the medial epicondyle of the humerus via a common flexor tendon.

The Anconeus extends the forearm.

The primary actions of the muscles in the anterior compartment of the forearm are wrist and finger flexion. These muscles include the palmaris longus, flexor carpi radialis, flexor digitorum superficialis, flexor carpi ulnaris, flexor digitorum profundus, and flexor pollicis longus.

Lateral epicondylitis, commonly known as tennis elbow, is a painful condition caused by trauma or overuse of the common extensor tendon of the posterior forearm muscles. It typically results from repeated forceful contractions of the forearm extensors, leading to pain at the lateral epicondyle of the humerus.

The retinacula are thickened, fibrous bands formed by the deep fascia of the forearm that help hold the tendons of the forearm muscles close to the bone. They prevent the tendons from 'bowstringing' outward, ensuring proper function during movement.

The muscles of the posterior compartment of the forearm primarily act as wrist and finger extensors. They extend the wrist, the metacarpophalangeal (MP) joints, and/or the interphalangeal (IP) joints. Key muscles include the extensor carpi radialis longus, extensor digitorum, and extensor carpi ulnaris.

The carpal tunnel is a tight space between the carpal bones and the flexor retinaculum where the flexor tendons of the digits and the median nerve pass through. This structure is significant as it can be a site of compression, leading to conditions such as carpal tunnel syndrome, affecting hand function.

The anterior forearm muscles can be subdivided into three groups:

1. Superficial Group: Includes muscles like brachioradialis, pronator teres, flexor carpi ulnaris, palmaris longus, and flexor carpi radialis.
2. Intermediate Group: Contains the flexor digitorum superficialis.
3. Deep Group: Comprises muscles such as supinator, flexor pollicis longus, pronator quadratus, and flexor digitorum profundus.

Carpal tunnel syndrome is a condition caused by compression of the median nerve or the tendons in the carpal tunnel. Common causes include inflammation of the tendons due to overuse, particularly in individuals who frequently flex their fingers or wrists, such as typists and computer programmers. It can also occur in pregnant women due to increased water retention.

Symptoms of carpal tunnel syndrome include pain, paresthesia (the sensation of 'pins and needles'), sensory loss, and motor loss in the muscles of the hand supplied by the median nerve. In severe cases, the muscles of the thumb may atrophy due to diminished nerve supply.

Treatment options for carpal tunnel syndrome include:

1. Supporting the hand in a splint
2. Administering anti-inflammatory drugs (e.g., ibuprofen)
3. In chronic cases that do not respond to conservative treatment, surgical incision of the flexor retinaculum to relieve pressure may be performed.

The anterior compartment of the forearm is divided into three layers:

1. Superficial layer: Includes pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris.
2. Intermediate layer: Contains the flexor digitorum superficialis.
3. Deep layer: Comprises flexor pollicis longus and flexor digitorum profundus, along with the pronator quadratus.

The flexor carpi radialis flexes the wrist and abducts (radial deviation) the hand at the wrist.

The flexor digitorum superficialis flexes the wrist, MP joints, and PIP joints of fingers 2-5 but does not cross the DIP joints, so it cannot move them. In contrast, the flexor digitorum profundus flexes the wrist, MP joints, PIP joints, and DIP joints of fingers 2-5.

The muscles in the posterior compartment of the forearm primarily function as wrist and finger extensors, with the exception of the supinator, which helps supinate the forearm.

The superficial layer of posterior forearm muscles includes:

1. Extensor carpi radialis longus: Extends the wrist and abducts the hand (radial deviation).
2. Extensor carpi radialis brevis: Works synergistically with the extensor carpi radialis longus.
3. Extensor digitorum: Extends the wrist, MP joints, PIP joints, and DIP joints of fingers 2-5.
4. Extensor digiti minimi: Extends the little finger.
5. Extensor carpi ulnaris: Extends the wrist and adducts the hand (ulnar deviation).

The abductor pollicis longus abducts the thumb and attaches to the first metacarpal.

The extensor indicis extends the MP, PIP, and DIP joints of the index finger (finger 2).

The posterior forearm muscles are divided into two groups:

1. Superficial Group:

   • Includes muscles such as Anconeus, Flexor carpi ulnaris, Extensor carpi ulnaris, Extensor digiti minimi, Brachioradialis, Extensor carpi radialis longus, Extensor carpi radialis brevis, Extensor digitorum, Abductor pollicis longus, and Extensor pollicis brevis.
   • Primary functions: Supinate the forearm and extend the wrist or fingers.

2. Deep Group:

   • Includes muscles such as Olecranon process of ulna, Supinator, Extensor pollicis longus, Extensor indicis, and Dorsal interossei.
   • Primary functions: Supinate the forearm and extend the wrist or fingers.

Flexes wrist and abducts hand

P: Medial epicondyle of humerus; D: Flexor retinaculum and palmar aponeurosis

Ulnar nerve (C8-T1)

Extends wrist, extends 2nd-5th MP joints, PIP joints, and DIP joints

P: Lateral epicondyle of humerus; D: Base of metacarpal V

Flexes MP joint of thumb, IP joint of thumb; weakly flexes wrist

Extensor carpi radialis longus, Extensor carpi radialis brevis, Extensor digitorum, Extensor digiti minimi, Extensor carpi ulnaris, Abductor pollicis longus, Extensor pollicis brevis, Extensor pollicis longus, Extensor indicis

Flexes wrist, 2nd-5th MP joints, and PIP joints

Abducts thumb, extends wrist (weakly)

P: Posterior surface of ulna; interosseous membrane; D: Distal phalanx of thumb

The intrinsic muscles of the hand are divided into three groups:

1. Thenar group - forms the thick, fleshy mass (thenar eminence) at the base of the thumb.
2. Hypothenar group - forms a smaller fleshy mass (hypothenar eminence) at the base of the little finger.
3. Midpalmar group - occupies the space between the thenar and hypothenar groups.

The intrinsic muscles of the hand allow for fine, controlled movements necessary for activities such as writing, typing, and playing a guitar.

The dorsal interossei muscles:

1. Abduct fingers 2-5.
2. Flex the MP joints of fingers 2-5.
3. Extend the PIP and DIP joints of fingers 2-5.

The adductor pollicis muscle adducts the thumb.

The palmar interossei muscles:

1. Adduct fingers 2, 4, and 5.
2. Flex the MP joints of fingers 2-5.
3. Extend the PIP and DIP joints of fingers 2-5.

The muscles involved in hand abduction (radial deviation) include:

• Flexor carpi radialis
• Extensor carpi radialis brevis
• Extensor carpi radialis longus
• Abductor pollicis longus
• Abductor pollicis brevis

The muscles involved in hand adduction (ulnar deviation) include:

• Extensor carpi ulnaris
• Flexor carpi ulnaris

The actions of the extensor carpi radialis muscles include:

• Wrist extension
• Radial deviation (abduction of the hand)

The muscles that flex the forearm at the elbow include:

• Biceps brachii
• Brachialis
• Brachioradialis

The major movements at the pelvic girdle and lower limb include:

1. Flexion and extension of the thigh at the hip joint.
2. Abduction and adduction of the thigh.
3. Medial and lateral rotation of the thigh.
4. Flexion and extension of the leg at the knee joint.
5. Dorsiflexion and plantarflexion of the foot at the ankle joint.

The gluteus maximus is the chief extensor of the thigh and laterally rotates the thigh.

The gluteus medius is a powerful abductor of the thigh and also medially rotates it.

The hamstring muscles include the biceps femoris, semimembranosus, and semitendinosus. Their primary function is to extend the thigh and flex the knee.

The tensor fasciae latae abducts and medially rotates the thigh.

The muscles that laterally rotate the thigh include the piriformis, superior gemellus, obturator internus, inferior gemellus, and quadratus femoris.

The hamstring muscles share a common proximal attachment to the ischial tuberosity of the os coxae.

The iliotibial tract (or IT band) is a lateral thickening of the fascia lata that extends from the iliac crest to the lateral condyle of the tibia, and it is important for stabilizing the knee during movement.

The gluteus maximus and the tensor fasciae latae attach to the iliotibial tract.

The muscles that adduct the thigh include the adductor longus, adductor brevis, adductor magnus, and gracilis. They are found in the medial compartment of the thigh.

The muscles that laterally rotate the thigh include the piriformis, superior gemellus, obturator internus, inferior gemellus, and quadratus femoris. They generally attach to the greater trochanter of the femur.

The muscles that extend the thigh include the gluteus maximus, biceps femoris (long head), semitendinosus, and semimembranosus.

Flexes thigh

Proximal: Iliac fossa; Distal: Lesser trochanter of femur with psoas major

Femoral nerve (L2-L3 fibers)

Proximal: Iliac crest, sacrum, coccyx; Distal: Iliotibial tract of fascia lata; linea aspera and gluteal tuberosity of femur

Superior gluteal nerve (L4-S1)

Abducts thigh; medially rotates thigh

The Piriformis muscle laterally rotates the thigh.

Proximal attachment: Ischial tuberosity; Distal attachment: Posterior surface of medial condyle of tibia.

The muscles responsible for thigh extension include the Gluteus maximus and the long head of the Biceps femoris.

The Quadratus femoris muscle is innervated by the nerve to quadratus femoris (L5-S1).

The Iliopsoas muscle is an agonist for hip flexion.

The Semitendinosus muscle extends the thigh and flexes the leg; it also medially rotates the leg.

The muscles involved in lateral rotation of the thigh include the Piriformis, Superior gemellus, Obturator internus, Inferior gemellus, and Quadratus femoris.

The Biceps femoris muscle extends the thigh (long head only), flexes the leg (both heads), and laterally rotates the leg.

The Gluteus medius muscle is responsible for medial rotation of the thigh.

The Adductor magnus muscle performs adduction and also has a hamstring part that extends the thigh.

The thigh muscles are divided into three main compartments:

1. Anterior (Extensor) Compartment:

   • Contains the quadriceps femoris, which is the agonist of knee extension.
   • Also includes the sartorius, which flexes and laterally rotates the thigh while flexing the leg.

2. Medial (Adductor) Compartment:

   • Contains muscles that adduct the thigh, such as the gracilis, which also flexes the leg.

3. Posterior (Flexor) Compartment:

   • Contains the hamstring muscles, which flex the leg.
   • Includes the biceps femoris, semitendinosus, and semimembranosus.

The quadriceps femoris is the great extensor muscle of the leg. It:

• Extends the knee during activities such as standing up, taking a step, or kicking a ball.
• Works with the iliopsoas to flex the hip when the leg is off the ground.

The sartorius muscle:

• Is the longest muscle in the body, projecting obliquely across the anterior thigh.
• Acts on both the hip and knee joints by:
  • Flexing the thigh at the hip.
  • Flexing the leg at the knee.
  • Laterally rotating the thigh.
• Nicknamed the 'tailor's muscle' because it helps in sitting cross-legged.

The hamstring muscles:

• Include the biceps femoris, semitendinosus, and semimembranosus.
• Primarily function to flex the leg at the knee.
• The biceps femoris has two heads:
  • The long head attaches to the ischial tuberosity and can laterally rotate the leg when flexed.
  • The short head attaches to the linea aspera of the femur and assists in leg flexion but does not move the thigh.

The muscles of the anterior thigh primarily flex the thigh and extend the leg.

The Iliacus and Psoas major are part of the iliopsoas group.

The three muscles that contribute to leg extension are Rectus femoris, Vastus lateralis, and Vastus medialis.

The Tensor fasciae latae helps in stabilizing the hip and knee during movement.

The Rectus femoris is known for its role in hip flexion and is part of the quadriceps group.

The primary muscles involved in extending the thigh include the gluteus maximus, semimembranosus, semitendinosus, and the long head of the biceps femoris. Note that the short head of the biceps femoris does not participate in thigh extension.

The gluteus medius is located on the iliac crest and plays a crucial role in stabilizing the hip during movement.

The hamstrings group, which includes the semitendinosus, semimembranosus, and biceps femoris, primarily functions to extend the thigh and flex the leg.

The adductor magnus primarily functions to adduct the thigh, but it also assists in extending the thigh.

The semitendinosus and semimembranosus muscles primarily medially rotate the leg when it is flexed and assist in flexing the leg at the knee joint.

The anterior compartment leg muscles primarily dorsiflex the foot and extend the toes. Key muscles include:

1. Extensor digitorum longus - Dorsiflexes the foot and extends toes 2-5.
2. Extensor hallucis longus - Dorsiflexes the foot and extends the great toe.
3. Fibularis tertius - Dorsiflexes and weakly everts the foot.
4. Tibialis anterior - Primary dorsiflexor and inverts the foot.

The lateral compartment leg muscles consist of two powerful evertors of the foot and weak plantar flexors:

1. Fibularis longus - A superficial muscle that covers the fibula and attaches to the plantar side of the foot.
2. Fibularis brevis - Lies deep to the fibularis longus and attaches to the base of the fifth metatarsal.

The gastrocnemius and soleus muscles, collectively known as the triceps surae, are the most powerful plantar flexors of the foot. They share a common distal attachment tendon, the calcaneal tendon (or Achilles tendon). The gastrocnemius also flexes the leg at the knee joint, while the soleus primarily plantar flexes the foot.

A groin pull is an injury caused by tearing, stretching, or straining the proximal attachments of the medial muscles of the thigh, particularly the adductor muscles and/or the iliopsoas muscle. It often results from activities involving rapid accelerations, such as in football, baseball, tennis, running, and soccer.

Strained or pulled hamstrings commonly occur in athletes who perform quick starts and stops, run fast, or experience sudden lateral or medial stress to the knee joint. The biceps femoris is particularly susceptible to this type of stress injury, which can lead to avulsion of the hamstring tendons from their attachment on the ischial tuberosity.

The Rectus femoris muscle extends the leg and flexes the thigh.

The Vastus intermedius muscle is innervated by the Femoral nerve (L2-L4).

The hamstrings group includes the biceps femoris, semimembranosus, and semitendinosus. Their primary action is to extend the thigh and flex the leg, while also rotating the leg laterally.

The proximal attachment of the Vastus lateralis muscle is at the greater trochanter and linea aspera, and the distal attachment is at the quadriceps tendon to the patella and then the patellar ligament to the tibial tuberosity.

The Sartorius muscle flexes the thigh and rotates it laterally, as well as flexing the leg and rotating it medially.

The anterior muscles of the leg primarily dorsiflex the foot and extend the toes.

The anterior leg muscles include:

1. Tibialis anterior
2. Extensor digitorum longus
3. Fibularis tertius
4. Extensor hallucis longus

The fibularis longus and fibularis brevis muscles primarily function to evert and plantar flex the foot.

The posterior muscles of the leg primarily plantar flex the foot and flex the toes.

The superficial posterior compartment includes the Plantaris, Gastrocnemius (lateral and medial heads), and Soleus.

The deep posterior compartment includes the Popliteus, Tibialis posterior, Flexor digitorum longus, Flexor hallucis longus, and Fibularis longus.

The Calcaneal tendon and Fibular retinaculum are key anatomical structures associated with plantar flexion of the foot.

The muscles of the posterior leg contribute to movement by enabling plantar flexion of the foot and flexion of the toes, which are essential for activities like walking and running.

The flexor digitorum longus plantar flexes the foot and flexes the MP, PIP, and DIP joints of toes 2-5.

The flexor hallucis longus plantar flexes the foot and flexes the great toe.

The tibialis posterior plantar flexes and inverts the foot.

The popliteus flexes the leg and medially rotates the tibia to unlock the fully extended knee joint.

The extensor digitorum longus is innervated by the deep fibular nerve (L4-S1).

Proximal attachment: Superior posterior surfaces of lateral and medial condyles of femur; Distal attachment: Calcaneus (via calcaneal tendon).

1. Gastrocnemius
2. Soleus
3. Plantaris

The fibularis longus everts the foot and acts as a weak plantar flexor.

The tibialis anterior dorsiflexes the foot and inverts the foot.

Many thigh and leg muscles are involved with leg flexion, including the gastrocnemius and popliteus.

The intrinsic muscles of the foot are divided into a dorsal group and a plantar group. The dorsal group contains the extensor hallucis brevis, which extends the MP joint of the great toe, and the extensor digitorum brevis, which extends the MP, PIP, and DIP joints of toes 2-4. These muscles support the arches and aid in toe movement for locomotion.

Plantar fasciitis is an inflammation of the plantar aponeurosis, often occurring at its attachment on the calcaneus bone. Common causes include:

1. Overexertion stressing the plantar fascia
2. Age-related loss of elasticity in the aponeurosis
3. Weight-bearing activities (e.g., jogging, lifting)
4. Excessive body weight
5. Improperly fitting shoes
6. Poor biomechanics (e.g., high-heeled shoes, flat feet) This condition is the most common cause of heel pain in runners.

Shin splints, or shin splint syndrome, refer to soreness or pain along the tibia. Causes include:

1. Tendonitis involving anterior compartment muscles, often the tibialis anterior
2. Inflammation of the periosteum (periostitis) This condition is common in runners who are new to the sport, poorly conditioned, wear ill-fitting shoes, or run on hard surfaces.

Compartment syndrome occurs when blood vessels within a limb compartment become compressed due to inflammation and swelling from muscle strain or trauma. This leads to increased pressure, compromising blood flow and nerve function. Potential consequences include:

• Ischemia (reduced blood flow) leading to hypoxia (lack of oxygen)
• Death of nerves within 2 hours
• Death of skeletal muscle within 6 hours Mild cases may be treated with rest, while severe cases may require surgical intervention to relieve pressure.

The gluteus minimus causes medial rotation of the thigh.

The plantar aponeurosis is formed from the deep fascia of the foot and extends between the phalanges of the toes and the calcaneus. It provides support to the plantar surface by enclosing the plantar muscles and maintaining the integrity of the foot's arch.

The flexor digitorum brevis attaches to the middle phalanges of toes 2-5, allowing it to flex the metatarsophalangeal (MP) and proximal interphalangeal (PIP) joints, but it does not flex the distal interphalangeal (DIP) joints.

The abductor hallucis is responsible for abducting the great toe (1), while the abductor digiti minimi abducts the small toe (5).

Extends the MP joint of the great toe (1).

Medial plantar nerve (S2-S3).

The abductor hallucis abducts the great toe and is innervated by the medial plantar nerve (S2-S3).

Pulls on flexor digitorum longus tendons to flex toes 2-5.

The supraspinatus muscle is the most commonly injured rotator cuff muscle due to its location in the narrow space between the acromion and the humerus. Repetitive arm motions can impinge the muscle in this space, potentially leading to tears.

The brachialis is an anterior arm muscle that primarily flexes the elbow joint.

The iliopsoas cannot flex the leg because it does not cross over the knee joint.

The extensor digitorum longus is a leg muscle that attaches to toes 2-5 and helps move them all.