Vastus Medialis: Origin, Insertion, Nerve & The "Teardrop" Muscle

The Vastus Medialis is one of the four quadriceps muscles, located on the inner (medial) aspect of the thigh. It is famous for its "teardrop" shape just above the knee. While it extends the knee, its most critical role is stabilizing the kneecap (patella) to prevent dislocation.

[Image of Rectus Femoris muscle anatomy]

Quick Anatomy Snapshot

Group	Quadriceps Femoris (Anterior Thigh).
Origin (Proximal)	Lower part of Intertrochanteric Line, Spiral Line, Medial Supracondylar Line, and Medial Lip of the Linea Aspera of the Femur.
Insertion (Distal)	Medial border of the Patella and Tibial Tuberosity (via the Patellar Ligament).
Nerve Supply	Femoral Nerve (L2, L3, L4).
Blood Supply	Femoral Artery and Profunda Femoris Artery.
Primary Actions	Knee Extension: Straightens the leg (especially the final 15-20 degrees). Patellar Tracking: Pulls the patella medially to prevent lateral dislocation.

Deep Dive: Two Muscles in One?

Clinicians often divide the Vastus Medialis into two functional parts based on fiber direction.

1. Vastus Medialis Longus (VML)

These are the upper fibers. They run vertically (15-20 degree angle) and act primarily as a knee extensor.

2. Vastus Medialis Obliquus (VMO)

These are the distal (lower) fibers that form the "teardrop" shape. They run horizontally (50-55 degree angle). Their primary job is NOT extension, but rather to pull the patella medially to keep it centered in the femoral groove.

Physio Corner: Clinical Relevance

💪 Functional Fact: The VMO is often the first muscle to atrophy (weaken) after knee surgery or injury and the last to recover. This weakness disrupts patellar tracking, leading to Patellofemoral Pain Syndrome (PFPS).

Palpation

Have the patient sit or lie supine with a towel roll under the knee (knee slightly flexed). Ask them to push the back of their knee into the towel (isometric extension). The VMO is the soft, fleshy mass palpated just medial and superior to the patella.

⚠️ Clinical Pathology: Runner's Knee
If the Vastus Lateralis (outer quad) is tight and the VMO is weak, the kneecap is pulled laterally off-track. This causes grinding and pain under the kneecap, known as Chondromalacia Patellae or Runner's Knee.

Manual Muscle Testing (MMT)

While we test the Quadriceps as a group, we focus on the last few degrees of extension for the VMO.

Testing Tip: "Terminal Knee Extension" (TKE). The VMO is most active in locking the knee straight during the final 15-20 degrees of extension.

Step-by-Step Procedure (Oxford Scale)

Grade	Patient Action & Resistance
Grade 3, 4, 5 (Against Gravity)	Position: Sitting, legs dangling. Action: Patient fully extends the knee (locks it out). Resistance: Applied at the distal anterior leg, trying to bend the knee. Grade 3: Completes full range (lockout). Grade 4/5: Holds lockout against resistance.
Grade 2 (Gravity Eliminated)	Position: Side-lying. Test leg is uppermost. Action: Patient extends the knee. Result: Full range of motion.
Grade 0, 1 (Palpation)	Action: Palpate the "teardrop" medial to the patella. Cue: "Try to squash the towel under your knee." Grade 1: VMO fires/bulges. Grade 0: No activity.

Frequently Asked Questions

Can you isolate the VMO?

Not entirely. Since the VMO and VML share the same nerve supply, it is difficult to fire one without the other. However, exercises like Terminal Knee Extensions (TKEs) and squats with a ball squeeze between the knees can bias recruitment toward the VMO.

Does it flex the hip?

No. The Vastus Medialis originates on the Femur, not the pelvis. Therefore, it does not cross the hip joint and has no action on it. Only the Rectus Femoris flexes the hip.

Why is the "Teardrop" shape important?

The presence of the "teardrop" indicates good muscle tone and hypertrophy. Loss of this definition is a quick visual sign of quadriceps atrophy or knee pathology.

Test Your Knowledge: Vastus Medialis Quiz

1. What is the specific function of the VMO fibers?

2. Where does the Vastus Medialis insert?

3. Which nerve supplies the Vastus Medialis?

4. The VMO is essential for preventing:

5. Where does the Vastus Medialis originate?

6. What distinguishes VMO fibers from VML fibers?

7. Does Vastus Medialis flex the hip?

8. The Vastus Medialis is part of which compartment?

9. Which range of motion is critical for VMO strengthening?

10. True or False: The Vastus Medialis is the deepest quadriceps muscle.

References

• Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2018). Clinically Oriented Anatomy. 8th ed. Philadelphia: Wolters Kluwer.
• Standring, S. (2016). Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41st ed. Elsevier.
• Magee, D. J. (2014). Orthopedic Physical Assessment. 6th ed. Elsevier.