📚 Question Bank

In the given clinical scenario, the inferior gluteal nerve is likely to be injured.

The gluteus maximus is innervated by the inferior gluteal nerve. Injury to the nerve causes atrophy of the muscle causing weakness in the extension of the thigh. The patients typically have a gluteus maximus lurch.

The gluteus maximus may be tested by extension of the hip against resistance, in the supine or prone position.

The gluteus medius muscle is attached to the lateral surface of the greater trochanter.

• Greater trochanter: It is a large and quadrangular projection arising from the junction of the neck and shaft of the femur. Muscles inserted into it are -
• Gluteus minimus
• Gluteus medius
• Piriformis
• Common tendon of obturator internus and gamelli.
• Lesser trochanter: It is a conical projection of the shaft present posteromedially. Muscles inserted to it are iliacus and psoas major

Surface marking: Greater trochanter lies inferior to the midpoint of the iliac crest and at the level of the horizontal plane passing through the pubic tubercle.

The iliotibial tract receives the insertion of tensor fasciae latae.

The iliotibial tract is the modification of the deep fascia of the thigh. The proximal end gives attachment to the tensor fascia lata and gluteus maximus. The distal end is attached to Gerdy’s tubercle present on the lateral condyle of the tibia.

The powerful abductor of hip joint is the gluteus medius. Abduction is assisted by the following muscles:

• Gluteus minimus
• Tensor fascia lata
• Piriformis
• Sartorius

Adduction of the hip joint is mainly caused by

• Adductor longus
• Adductor brevis
• Adductor magnus
• Gracilis

Flexion of the hip joint is caused by:

• Psoas major
• Iliacus
• Rectus femoris
• Assisted by:
• Pectineus
• Tensor fascia lata
• Sartorius

Extension of the hip joint is caused by:

• Gluteus maximus
• Biceps femoris
• Semitendinosus
• Semimembranosus (hamstrings)
• Adductor magnus
• Assisted by - posterior fibers of gluteus medius

The external rotation of the hip joint is caused by the following muscles:

• Gluteus maximus
• Obturator internus
• Superior and inferior gemelli
• Quadratus femoris
• Piriformis
• Assisted by
• Obturator externus
• Sartorius

Internal rotation of the hip joint is caused by the following muscles:

• Gluteus medius
• Gluteus minimus
• Tensor fascia lata
• Adductor muscles

The posterior femoral muscles (hamstring muscles) are innervated by the sciatic nerve.

• Semitendinosus, semimembranosus, and the long head of biceps femoris are innervated by tibial division of the sciatic nerve (L5, S1, and S2)
• The short head of biceps femoris is innervated by the common peroneal division of the sciatic nerve.

The short head of the biceps femoris is not attached to the ischial tuberosity. It is attached to the lateral lip of the linea aspera, lateral supracondylar ridge of the femur, and the lateral intermuscular septum of the thigh.

The ischial tuberosity is broadly divided into upper and lower areas:

• The upper area is further subdivided into a superolateral part for the semimembranosus and an inferomedial part for the long head of the biceps femoris and the semitendinosus.
• The lower area is subdivided by an irregular vertical ridge, into lateral and medial areas. The larger lateral area is for the adductor magnus. The smaller medial area is covered by adipose tissue, which usually contains the sciatic bursa of the gluteus maximus, which supports the body in sitting.

The clinical features are suggestive of piriformis syndrome, which occurs due to the entrapment of the sciatic nerve.

It is triggered by sitting for a long time or running, climbing stairs, or applying firm pressure directly over the piriformis muscle. Early signs include pain, tingling, or numbness in the buttocks. Later it may lead to severe pain extending down the length of the sciatic nerve.

The sartorius muscle is not a part of hamstring muscles.

Hamstring muscles are present in the posterior compartment of the thigh and include semimembranosus, semitendinosus, and biceps femoris.

They cause the flexion of the knee joint and extension of the hip joint. In addition to this, semimembranosus and semitendinosus cause medial rotation of the hip and knee joint, and biceps femoris causes lateral rotation of the hip and knee joint.

The gracilis muscle belongs to the medial compartment of the thigh. Muscles of the anterior compartment:

• Sartorius
• Rectus femoris
• Vasti medialis, lateralis, and intermedius
• Articularis genus
• Note:

Adductor longus and pectineus are sometimes considered to be part of both the anterior and the medial compartments.

The weakness of the vastus medialis is responsible for the lateral displacement of the patella.

The lowest fibers of the vastus medialis muscle, which are attached medially to the upper half of the patella are referred to as vastus medialis obliquus. These fibers of the vastus medialis prevent the lateral displacement of the patella, during knee motion. The weakness of the vastus medialis obliquus may lead to patellar instability and pain.

Medial rotation of the flexed knee is produced by the following muscles:

• Semimembranosus
• Popliteus
• Semitendinosus
• Assisted by
• Sartorius
• Gracilis

Knee joint is a complex synovial joint consisting of tibiofemoral and patellofemoral articulations. Movements occurring at knee joint are flexion, extension, medial rotation, and lateral rotation.

• Flexion - biceps femoris, semitendinosus, and semimembranosus (hamstrings)
• Extension - quadriceps femoris, assisted by tensor fasciae latae
• Medial rotation of the flexed leg - popliteus, semimembranosus, and semitendinosus
• Lateral rotation of the flexed leg - biceps femoris

Note: Semimembranosus tendinopathy may develop as a result of the overuse of muscle usually cyclists and marathon runners. Patients may complain of insidious pain in the posteromedial part of the knee radiating distally to the medial calf or proximally to the posteromedial thigh. It is a cause of chronic knee pain that often goes undiagnosed as it is poorly understood.

In the given scenario, the muscle likely to be affected is extensor hallucis longus, which is innervated by the deep peroneal nerve.

Peroneus brevis muscle belongs to the lateral compartment of the leg.

Muscles of the anterior compartment of the leg produce dorsiflexion (extension) of the ankle. They are:

• Extensor digitorum longus
• Extensor hallucis longus
• Tibialis anterior
• Peroneus tertius (inverts and everts foot)

Muscles of the posterior compartment produce plantar flexion. They include superficial and deep groups which are separated by the transverse intermuscular septum.

• The superficial flexor group consists of the gastrocnemius, plantaris, and soleus.
• The deep flexor group consists of popliteus, flexor digitorum longus, flexor hallucis longus, and tibialis posterior.

Muscles of lateral compartment evert the ankle and include peroneus longus and peroneus brevis.

The action shown in the image is plantar flexion of the ankle joint and weakness of gastrocnemius muscle causes loss of this movement.

The plantar flexion of the toe is produced mainly by gastrocnemius and soleus, assisted by plantaris, tibialis posterior, flexor hallucis longus, and flexor digitorum longus.

Dorsiflexion is caused by the tibialis anterior and assisted by extensor digitorum longus, extensor hallucis longus, and peroneus tertius.

The gastrocnemius (two heads) and soleus muscles are collectively known as triceps surae. They constitute a powerful muscular mass whose main function is plantar flexion of the foot.

The main bulk of the calf is formed by gastrocnemius, plantaris, and soleus muscles. These 3 muscles form the superficial flexor group of the posterior compartment of the lower leg.

Dorsiflexion of the foot causes pain in the deep posterior compartment syndrome of the leg.

All tibial fractures should be monitored for signs of compartment syndrome. Severe pain is the most important clinical feature. Regular clinical evaluation is important because swelling, blistering, and skin necrosis is associated with late, severe compartment syndrome.

Compartment syndromes of the lower limb:

• Superficial and deep posterior compartment syndrome - There will be pain on passive dorsiflexion of the foot and on the toe extension
• Anterior compartment syndrome - There will be pain on passive plantar flexion of the foot and toe flexion
• Lateral compartment syndrome - There will be pain on passive foot inversion.

The first layer of the sole consists of abductor hallucis.

The muscles of the sole of the foot are arranged in 4 layers. From superficial to deep, the layers are numbered from one to four.

Muscles of the sole of the foot are:

1st layer: This is the superficial layer which includes abductor hallucis, abductor digiti minimi, and flexor digitorum brevis.

2nd layer: It consists of flexor accessorius and the four lumbrical muscles,the tendons of flexor hallucis longus and flexor digitorum longus run in the same plane as the muscles of the second layer.

3rd layer: It contains the shorter intrinsic muscles of the toes, which are flexor hallucis brevis, adductor hallucis and flexor digiti minimi brevis.

4th layer: It consists of plantar and dorsal interossei and the tendons of tibialis posterior and fibularis longus.

The femoral nerve is a branch of the lumbar plexus and arises from the posterior (dorsal)

divisions of the ventral rami of L2–L4.

The sciatic nerve, posterior femoral cutaneous nerve, and nerve to obturator internus are a part of sacral plexus.

The given scenario is suggestive of meralgia paresthetica, in which the lateral cutaneous nerve of the thigh is affected. The root value of this nerve is L2 and L3.

It arises from the posterior divisions of the ventral rami of L2 and L3 and supplies the skin of the anterior and lateral surfaces of the thigh upto the knee.

The images given below represent the root value and the area supplied by the lateral cutaneous nerve of the thigh.

The sciatic nerve is a branch of the sacral plexus. It is the largest branch of the sacral plexus.

The femoral nerve is split into the anterior and posterior divisions by the lateral circumflex femoral artery.

The course of femoral nerve is given below:

• Arises from posterior division of ventral rami of L2-L4 spinal segments on the posterior abdominal wall
• Enters the femoral triangle by passing under the inguinal ligament
• In the femoral triangle, it lies lateral to the femoral artery and outside the femoral sheath
• Divided into anterior and posterior branches by lateral circumflex femoral artery

Note: Obturator nerve is divided into anterior and posterior divisions by obturator externus in the upper part and adductor brevis in the lower part.

The Nerve to pectineus arises near and passes below the inguinal ligament and then runs behind the femoral sheath.

The femoral nerve gives off the nerve to iliacus and pectineus before it divides into the anterior and posterior divisions.

The image given below shows the course of the femoral nerve.

Gracilis is supplied by the obturator nerve and not the femoral nerve. Hence, the function of gracilis muscle will be normal in this patient.

Branches of the femoral nerve:

• Before entering the thigh, the femoral nerve supplies branches to the iliacus and pectineus muscles
• The anterior division of femoral nerves supplies the sartorius and gives sensation to

the anteromedial aspect of the thigh by the branches medial cutaneous nerve of the thigh and intermediate cutaneous nerve of the thigh

• The posterior division of the femoral nerve supplies branches to the quadriceps femoris muscles, knee joint and gives sensation to the medial aspect of the leg by the saphenous nerve.

The image given below shows the course of the femoral nerve.

Loss of extension of the knee joint with decreased sensation over the anterior aspect of the thigh suggests damage to the femoral nerve.

The femoral nerve innervates the quadriceps femoris muscles which are the extensors of the knee joint. It provides sensory branches to the anterior and medial aspect of the thigh by medial and intermediate cutaneous nerves of the thigh.

The image given below shows the course of the femoral nerve.