Kinesiology of the Knee:
By Dr. Brent Brookbush DPT, PT, MS, CPT, HMS, IMT
From the Course:
Additional Courses
- Lesson 13: Hip Flexors and Anterior Thigh Muscles (Introductory Course)
- Knee Joint Anatomy: Tibiofemoral and Patellofemoral Joints (Advanced Course)
Definitions:
- Prime Mover : The muscle that can produce the most force for a joint action. Generally, this is the muscle that will generate the most force during a joint action when exerting force against an external load.
- Agonist : Muscles that perform a joint action, including the prime mover and synergists. That is, unlike the terms prime mover and synergist, agonist refers to all of the muscles that can perform a joint action.
- Synergist : Synergists are muscles that assist the prime mover in performing a joint action. By definition, all agonists that are not the prime mover are synergists.
- Antagonist : Muscles that oppose the agonists (including the prime mover and synergists) for a given joint action. That is, all of the muscles that can perform the opposing joint action.
- Neutralizer : During a joint action, neutralizers are muscles that oppose the unwanted or ancillary joint motions that result from the force generated by the prime mover and/or synergists.
- Fixator : Fixators are muscles that act to reduce or prevent movement of joints proximal to the joint in motion.
- Stabilizer : The role of a stabilizer is to improve arthrokinematics by maintaining optimal alignment of joint surfaces during joint actions. Most often, these muscles are the most intrinsic muscles of a joint. For example, the muscles of the rotator cuff of the shoulder.
Kinesiology of the Knee Joint
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 exist - for example, the short head of the biceps femoris and vastus medialis obliquus are functional antagonists.
- Stabilizers:
- Medial stabilizers - Pes Anserinus group, medial gastrocnemius , and vastus medialis obliquus
- Lateral Stabilizers - Gluteus maximus , TFL , and vastus lateralis via the iliotibial band, 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 the invertors of the ankle.