Muscles of the Hip and Knee: Anatomy, Categorization, and Clinical Examination

Comprehensive vocabulary flashcards covering muscle categorization, anatomy, attachments, actions, innervations, palpation landmarks, and clinical examination techniques for the hip and knee.

Category A Muscles

Muscles requiring high-detail knowledge, including morphology (shape and fiber arrangement), proximal and distal attachments, actions and functions, and nerve supply (e.g., Gluteus Maximus).

Category B Muscles

Muscles requiring moderate-detail knowledge focusing specifically on attachments as well as actions and functions (e.g., Gluteus Medius).

Category C Muscles

Muscles requiring basic knowledge limited to their anatomical location and primary function (e.g., Sartorius).

Gluteus Maximus

A large quadrilateral Category A hip extensor attaching proximally to the gluteal surface, posterior ilium, iliac crest, sacrum, coccyx, and sacrotuberous ligament, and distally to the iliotibial tract and gluteal tuberosity; innervated by the inferior gluteal nerve.

Gluteus Medius

A fan-shaped Category B abductor located deep to the gluteus maximus and superficial to the gluteus minimus; attaches proximally to the gluteal surface of the ilium and distally to the greater trochanter, stabilizing the pelvis during closed kinetic chain movement.

Gluteus Minimus

A Category B muscle lying deep to the gluteus medius that attaches proximally to the gluteal surface of the ilium and distally to the greater trochanter, performing hip abduction, medial rotation, and lateral pelvic tilt stabilization.

Tensor Fasciae Latae

A Category B muscle attaching proximally to the iliac crest and ASIS and distally to the iliotibial tract; pulls on the IT band from the ilium to the tibia to mediate abduction and medial rotation.

Semitendinosus

A fusiform Category A hamstring muscle with a long tendon attaching proximally to the lower medial facet of the ischial tuberosity and distally to the anteromedial surface of the medial tibial condyle; innervated by the tibial branch of the sciatic nerve.

Semimembranosus

A fusiform Category A hamstring muscle underlying the semitendinosus that attaches proximally to the upper lateral facet of the ischial tuberosity and distally to the medial tibial condyle; innervated by the tibial branch of the sciatic nerve.

Biceps Femoris

A posterior lateral Category A hamstring muscle consisting of a fusiform long head (originating from the ischial tuberosity) and a quadrilateral short head (originating from the lateral lip of the linea aspera) that inserts on the fibular head and lateral tibial condyle.

Iliopsoas

A conjoined hip flexor formed by the merging of the psoas major (descending vertically from the spine) and the iliacus (originating laterally from the iliac fossa), inserting together into the lesser trochanter of the femur.

Iliacus

A large, fan-shaped Category A anterior hip flexor originating from the upper aspect of the posterior two-thirds of the iliac fossa and inserting into the lesser trochanter of the femur; innervated by the femoral nerve.

Psoas Major

A thick Category A muscle originating from the $T_{12}-L_5$ vertebral bodies, intervertebral discs, and transverse processes, inserting into the lesser trochanter of the femur to perform hip and lumbar flexion; innervated by anterior rami ($L_1-L_{3/4}$).

Rectus Femoris

A Category A quadriceps muscle with a bipennate fiber arrangement originating from the AIIS and superior acetabular ridge and inserting onto the tibial tuberosity; acts across two joints to produce hip flexion and knee extension.

Vastus Medialis

An anteromedial quadriceps muscle composed of vertically oriented upper fibers and horizontally oriented lower fibers; originates from the intertrochanteric line and medial lip of the linea aspera to extend the knee and stabilize the patella.

Vastus Lateralis

A lateral quadriceps muscle attaching proximally to the intertrochanteric line and lateral lip of the linea aspera, inserting onto the tibial tuberosity; innervated by the femoral nerve to perform knee extension and patella stabilization.

Vastus Intermedius

A deep quadriceps muscle situated beneath the rectus femoris and between vastus medialis and lateralis, originating from the anterior femoral shaft and inserting onto the tibial tuberosity to execute knee extension.

Sartorius

A Category C long strap muscle originating at the ASIS and inserting onto the proximal tibia below the condyle; causes thigh flexion, abduction, and external rotation at the hip, as well as leg flexion and internal rotation at the knee.

Gracilis

A Category C medial thigh muscle originating from the anterior body of the pubis and inserting into the medial proximal tibia; mediates hip flexion and adduction along with knee flexion and internal rotation.

Pectineus

A Category C muscle originating from the superior pubic ramus (pectineal line of pubis) and inserting onto the pectineal line and linea aspera of the femur; functions in hip flexion, adduction, and external/internal rotation.

Adductor Magnus

A Category B muscle featuring an adductor portion (from the inferior/ischial ramus to the linea aspera) and a hamstring portion (from the ischial tuberosity to the adductor tubercle of the medial femoral condyle).

Adductor Longus

A Category B muscle originating from the body of the pubis lateral to the pubic symphysis and inserting into the middle third of the linea aspera; acts in thigh adduction, hip flexion, and extension.

Adductor Brevis

A short Category B adductor muscle originating from the inferior pubic ramus and inserting onto the upper half of the linea aspera to adduct the thigh.

Popliteus

A deep muscle of the lower leg located on the posterior aspect of the knee joint that participates in knee flexion.

Piriformis

A Category C lateral hip rotator originating from sacral segments 2 through 4 ($S_2-S_4$) and inserting onto the greater trochanter of the femur.

Gemellus

A pair of Category C lateral rotators inserting onto the greater trochanter; the superior gemellus arises from the gluteal surface of the ischial spine, whereas the inferior gemellus originates from the ischial tuberosity.

Obturator Internus

A Category C lateral rotator originating from the inferior margin of the superior pubic ramus and the pelvic surface of the obturator membrane, inserting onto the greater trochanter.

Trendelenburg Test

A clinical examination maneuver assessing closed-chain lateral pelvic tilt and abductor stability mediated by the gluteus medius and gluteus minimus.

Muscle Strength Grade 0

The lowest score on the manual muscle testing scale, characterized by the complete absence of any muscular contraction.

Muscle Strength Grade 1

A score on the manual muscle testing scale denoted by a faint trace, flicker, or palpable muscle contraction without joint motion.

Muscle Strength Grade 2

A score on the manual muscle testing scale where the muscle produces active movement through full range only when gravity is eliminated.

Muscle Strength Grade 3

A score on the manual muscle testing scale representing active joint motion against the resistance of gravity alone.

Muscle Strength Grade 4

A score on the manual muscle testing scale indicating active movement against gravity accompanied by moderate external resistance.

Muscle Strength Grade 5

The highest score on the manual muscle testing scale, representing normal muscular power against gravity and full maximal resistance.

Two-Joint Muscle Flexibility Testing

A clinical examination protocol where each joint crossed by a multi-joint muscle is stretched and evaluated independently to assess flexibility (e.g., assessing hamstring flexibility via hip flexion with straight leg raise and knee extension at $90^\circ$).