Kinesiology of the Knee:

By Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS

Knee Extension:

• Prime Mover: Quadriceps - vastus lateralis, vastus medialis, vastus intermedius, rectus femoris
• Synergists: There are no true synergists of knee extension. However, the gluteus maximus and soleus could be viewed as synergists to knee extension during closed chain mechanics.
• Antagonists: Biceps Femoris, semimembranosus, semitendinosus, popliteus, gastrocnemius, gracilis, sartorius
• Neutralizers: Careful balance between medial and lateral stabilizers of the knee must be maintained to prevent excessive internal or external rotation of the tibia. More complex relationships between synergistic pairs exist - for example, the short head of the biceps femoris and vastus medialis obliquus are functional antagonists.
• Stabilizers:

  • Medial stabilizers - Pes Anserinus group, semimembranosus, medial gastrocnemius, and vastus medialis obliquus, popliteus
  • Lateral Stabilizers - Gluteus maximus, TFL, and vastus lateralis via the iliotibial band, biceps femoris, and lateral gastrocnemius, plantaris
  • Popliteus, Articular muscle of knee

• Fixators: All muscles of the ankle, hip, and LPHC. Especially the intrinsic stabilization subsystem, the glute complex, and invertors of the ankle.

Knee Flexion:

• Prime Mover: Biceps femoris, semimembranosus, semitendinosus
• Synergists: popliteus, gastrocnemius, gracilis, sartorius
• Antagonists: Quadriceps - vastus lateralis, vastus medialis, vastus intermedius, rectus femoris
• Neutralizers: Careful balance between medial and lateral stabilizers of the knee must be maintained to prevent excessive internal or external rotation of the tibia. More complex relationships between synergistic pairs