Which muscle extends the knee and lies medially in the quadriceps group?

• A. Vastus Medialis
• B. Vastus Lateralis
• C. Rectus Femoris
• D. Vastus Intermedius

Answer: (A)

Understanding knee extension and the arrangement of the quadriceps helps identify which muscle is both responsible for extending the knee and located on the inner (medial) side of the group. All four parts of the quadriceps contribute to knee extension, but their positions differ. The vastus medialis runs along the medial aspect of the thigh, making it the inner portion of the group. When it contracts, it pulls on the quadriceps tendon and the patellar tendon to straighten the leg, with its medial placement giving it a key role in guiding the patella medially and stabilizing the knee. The other components lie laterally (vastus lateralis), deep between them (vastus intermedius), or centrally and across the hip (rectus femoris), so they don’t meet the “medial” criterion. Therefore, the muscle that extends the knee and lies medially in the quadriceps group is the vastus medialis.