What are the four quadriceps muscles?

Rectus femoris, vastus lateralis, vastus medialis and vastus intermedius. All four extend the knee. Rectus femoris is the only one that also crosses the hip, so it additionally acts as a hip flexor.

Do squats train all four quad heads?

They train the three vastus heads very well. The rectus femoris is trained less effectively, because it crosses the hip and is shortened at the hip during a squat. Adding leg extensions covers it.

How do I grow the teardrop above my knee?

That is the vastus medialis, and it is trained by any knee extension movement — there is no exercise that isolates it. Full-depth squats and leg extensions taken through a complete range are the most effective options. Terminal knee extensions are often recommended for it, but the research on selectively targeting it is weak.

How deep should I squat?

At least to parallel, meaning the hip crease level with the top of the knee, and deeper if your mobility allows it comfortably. Depth increases the range the quads and glutes work through, and deeper squats produce more growth than partial ones at equivalent effort.

Quadriceps: The 4 Heads, Anatomy and Best Exercises

Quads anatomy

All four quadriceps heads converge into the quadriceps tendon, which surrounds the kneecap and continues as the patellar tendon to the shin. Whatever the exercise, their shared job is straightening the knee.

The vastus lateralis on the outside is the largest of the four and gives the thigh its outer sweep. The vastus medialis on the inside includes the teardrop-shaped portion just above the knee. The vastus intermedius lies underneath the rectus femoris and is invisible from the surface.

The rectus femoris is the exception. It originates on the pelvis rather than the femur, so it crosses both the hip and the knee. This means it is at its most effective as a knee extensor when the hip is extended — which is why it works harder in a leg extension or a sissy squat than in a deep squat, where it is shortened at the hip.

Part	What it does
Rectus femoris	Crosses hip and knee. Also a hip flexor. Best trained with the hip extended.
Vastus lateralis	Largest head, outer thigh. Creates the outer sweep.
Vastus medialis	Inner thigh, including the teardrop above the knee.
Vastus intermedius	Deep, beneath the rectus femoris. Not visible but contributes real mass.

Origin: Rectus femoris: the anterior inferior iliac spine of the pelvis. Vastus lateralis, medialis and intermedius: the shaft and upper regions of the femur.
Insertion: The tibial tuberosity, via the quadriceps tendon, the patella and the patellar ligament.

What the quads does

Knee extension — straightening the leg. All four heads.
Hip flexion — raising the thigh, via the rectus femoris only.
Controlling knee flexion eccentrically — decelerating on the way down in a squat, a landing or a descent.
Stabilising the patella in its groove during knee movement.

Best quads exercises

Exercise	Equipment	Role	Level	Why
Back squat	Barbell	primary	Intermediate	The classic. Trains all four heads plus the glutes; loadable for years.
Front squat	Barbell	primary	Advanced	More upright torso shifts emphasis toward the quads and away from the hips.
Leg press	Machine	primary	Beginner	Heavy quad loading without the balance and lower-back demands of a squat.
Leg extension	Machine	primary	Beginner	The only common exercise that isolates knee extension, and the best way to load the rectus femoris.
Bulgarian split squat	Bench + dumbbells	primary	Intermediate	Single-leg quad and glute work with a long range of motion.
Hack squat	Machine	primary	Beginner	Fixed path lets you push the quads close to failure safely.
Walking lunge	Dumbbells	secondary	Beginner	Trains the quads through a long range with a substantial stability demand.

How to train the quads

Sets per week

12–20 hard sets

Rep range

5–10 for squats and presses, 10–20 for extensions

Frequency

2 sessions per week

Squat depth matters. Stopping above parallel drastically reduces the range the quads work through; going to at least parallel trains far more of the muscle.
Include a leg extension or similar if the rectus femoris matters to you — it is the head that compound squatting trains least well.
Heavy squats generate a lot of systemic fatigue. Two quad sessions a week with one heavy and one moderate tends to work better than two maximal ones.

Stretches and mobility

Standing quad stretch

Pull the heel toward the glute with the knee pointing down, hips square. 30 seconds each side.

Couch stretch

Rear foot elevated against a wall, front foot forward in a lunge. Stretches the rectus femoris and hip flexors together.

Common mistakes

Partial-range squatting

Quarter squats let you load a much bigger number, but they train a small fraction of the muscle's range. Going at least to parallel produces substantially more growth at a fraction of the weight.

Skipping leg extensions on principle

Leg extensions have a reputation as a 'non-functional' exercise, but they are the only common movement that trains the rectus femoris with the hip extended. That is a genuine gap in a squat-only programme.

Letting the knees cave inward

Knee valgus under load usually means the glutes are not contributing to hip external rotation. It is more often a strength and cueing issue than a mobility one.

Quads FAQ

What are the four quadriceps muscles?: Rectus femoris, vastus lateralis, vastus medialis and vastus intermedius. All four extend the knee. Rectus femoris is the only one that also crosses the hip, so it additionally acts as a hip flexor.
Do squats train all four quad heads?: They train the three vastus heads very well. The rectus femoris is trained less effectively, because it crosses the hip and is shortened at the hip during a squat. Adding leg extensions covers it.
How do I grow the teardrop above my knee?: That is the vastus medialis, and it is trained by any knee extension movement — there is no exercise that isolates it. Full-depth squats and leg extensions taken through a complete range are the most effective options. Terminal knee extensions are often recommended for it, but the research on selectively targeting it is weak.
How deep should I squat?: At least to parallel, meaning the hip crease level with the top of the knee, and deeper if your mobility allows it comfortably. Depth increases the range the quads and glutes work through, and deeper squats produce more growth than partial ones at equivalent effort.

Related muscles

Hamstrings

Biceps femoris, semitendinosus and semimembranosus

The hamstrings are three muscles on the back of the thigh: biceps femoris, semitendinosus and semimembranosus. They cross both the hip and the knee, so they do two jobs — bending the knee and extending the hip. Training only one of those leaves half the muscle undertrained.

Glutes

Gluteus maximus, medius and minimus

The glutes are three muscles. Gluteus maximus is the largest muscle in the human body and extends the hip — driving you up out of a squat and forward in a sprint. Gluteus medius and minimus sit higher and to the side, abducting the hip and stopping the pelvis dropping when you stand on one leg.

Adductors

Adductor magnus, longus, brevis, pectineus and gracilis

The adductors are five muscles on the inner thigh that pull the leg toward the midline. The largest, adductor magnus, is also one of the body's most powerful hip extensors — it contributes meaningfully to squats and deadlifts, which is why the inner thigh is far more than a stability muscle.

Calves

Gastrocnemius and soleus

The calf is two muscles. The gastrocnemius is the visible two-headed muscle that crosses both the knee and the ankle, so it only works fully with the leg straight. The soleus lies underneath, crosses only the ankle, and takes over when the knee is bent — which is why seated calf raises are not optional.

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