Kinetics of knee joint

Action of muscle forces on knee joint.

1. KINETICS OF KNEE JOINT

2. EXTENSORS RECTUS FEMORIS : 1. Bipennate 2. Attachment – Origin : ASIS and groove on ilium , superior to acetabulum Insertion : Aponeurosis of quadriceps to superior border of patella. 3. Knee extensor, hip flexor, hip lateral rotator, hip abductor. VASTUS INTERMEDIUS : 1. Unipennate . 2. Attachment - Origin : Anterior and lateral surfaces of upper 2 thirds of femoral shaft Insertion : Deep portion of aponeurosis of quadriceps attaching to lateral border of patella and lateral tibial condyle . 3. Throughout knee extension. 4. Deepest part of vastus intermedius is associated with articularis genu .

3. ARTICULARIS GENU - 1. Attachment – Origin : Anterior surface of lower shaft of femur. Insertion : Suprapatellar pouch. 2. Vastus intermedius pulls pouch proximally during knee extension, preventing impingement of pouch at patellofemoral joint. VASTUS LATERALIS – 1. Pennate muscle 2. Attachment – Origin : Intertrochanteric line, anterior & inferior borders of greater trochanter , lateral border of gluteal tuberosity , proximal half of linea aspera , lateral intermuscular septum. Insertion : Quadriceps aponeurosis attaching to lateral border & base of patella and patellar tendon. 3. Active throughout knee extension. 4. Recruitment is proportional to amount of resistance to extension.

4. VASTUS MEDIALIS – 1. 2 parts – Vastus medialis lateralis (VML) , Vastus medialis oblique (VMO). 2. Attachment – Origin : VML – distal half of intertrochanteric line, medial supracondylar line, medial lip of linea aspera , medial intermuscular septum. VMO – arises from tendon of adductor magnus . Insertion : Quadriceps aponeurosis , attaching to medial border of patella, VMO attaches directly to medial border of patella. 3. Throughout knee extension, patellar stabilization.

5. PATELLAR STABILIZATION Q angle therefore indicates That active contraction of Quadriceps pulls patella laterally and proximally. Althought there is no true translation reported. There are three systems of protection to stabilize the patella and prevent its lateralll deviation – Expanded surface of lateral condyle of femur. Medial extensor retinaculum . VMO.

6. FLEXORS Gastrocnemius also plays a role in knee flexion, although its main role is at knee joint.

7. HAMSTRING BICEPS FEMORIS – Origin: Long head – Medial surface of ischial tuberosity . Short head – Lateral lip of linea aspera , proximal half of lateral supracondylar line, lateral intermuscular septum. Insertion : Head of fibula, lateral collateral ligament, lateral condyle of tibia SEMITENDINOSIS – Origin - Inferior and medial surface of ischial tuberosity Insertion – Proximal aspect of medial surface of shaft ot tibia. SEMIMEMBRANOSUS – Origin – Lateral facet of ischial tuberosity . Insertion – Posterior and medial surfaces of medial tibial condyle .

8. HAMSTRINGS act as knee flexors, hip extensors, medial rotators, lateral rotators, hip medial and lateral rotators and hip adductor. The hamstrings provide active resistance to anterior glide of the tibia on the femur. Thus they are described as important adjuncts to the anterior cruciate ligament (ACL) and perhaps a critical substitute in the ACL-deficient knee. Hamstrings provide between 30 and 50% of hip extension strength.

9. Hamstrings are active during normal locomotion. The most prominent period of activity is at the transition between the swing and stance periods of the gait cycle. The knee flexion that occurs in late stance and early swing usually occurs without the activity of the hamstrings. It also is important to recognize that many activities in the erect posture that require knee flexion such as descending stairs and sitting down use the quadriceps femoris to control the flexion rather than the hamstrings to produce the flexion.

10. POPLITEUS – Origin : Lateral aspect of the lateral femoral condyle , popliteus tendon, arcuate ligament, and the fibrous capsule of the knee. The tendon may have an attachment to the lateral meniscus as well. Insertion :A triangular area on the posterior surface of the tibia proximal to the soleal line. EMG data reveal only slight activity of the popliteus during knee flexion. Its activity increases significantly when knee flexion is accompanied by medial rotation of the tibia, and isolated medial rotation of knee. The popliteus also contracts during gait when the tibia is medially rotating. Reinforces the posterior cruciate ligament, preventing posterior glide of the tibia, as well as rotations into varus and lateral rotation. Pulls the meniscus posteriorly during knee flexion, perhaps providing additional protection from tears.

11. MEDIAL ROTATORS OF KNEE

12. SARTORIUS – Origin : Anterior superior iliac spine and the proximal half of the notch below it . Insertion : Proximal aspect of the medial surface of the shaft of the tibia. Hip flexor, hip lateral rotator, hip abductor, knee flexor, tibia medial rotator. GRACILIS – Origin : inferior half of the body of the pubis, the inferior pubic ramus , and the ischial tuberosity . Insertion : Proximal aspect of the medial surface of the shaft of the tibia. Analysis of the moment arms of the gracilis support its role as both a flexor and medial rotator of the knee. Mechanical analyses demonstrate a large adduction moment arm at the hip, with a very small moment arm for lateral rotation.

13. PES ANSERINUS : These three muscles together appear to contribute to the dynamic stabilization of the knee against valgus and rotary forces. At least one of these three muscles of the pes anserinus is available to provide support to the knee regardless of the hip position. Each of the primary motor nerves innervates one of these muscles. Organization established to guarantee the availability of some dynamic stabilization of the medial side of the knee. Many sports activities require running and quick turning, including soccer and tennis

14. LATERAL ROTATORS

15. TENSOR FASCIA LATAE – Origin : iliac crest and anterior superior iliac spine and from the fascia lata. Insertion : Via the iliotibial band (ITB) to the lateral tubercle of the tibia. The ITB also attaches to the lateral condyle of the femur and head of the fibula and blends with the extensor expansion of the vastus lateralis . EMG data consistently reveal activity of the tensor fasciae latae during hip flexion, abduction, and medial rotation. it has a large hip abduction moment arm. Its hip flexion moment arm is larger than the moment arm of the iliopsoas . Like the muscles of the pes anserinus on the medial side of the knee, the tensor fasciae latae provides dynamic stabilization to the knee joint via its attachment into the iliotibial band, increasing its activity in the presence of forces tending to adduct the knee

16. REFERENCES Kinesiology mechanics and pathomechanics ; 2 nd edition. Carol. A. Oatis . Joint Structure and function; 5 th edition. Cynthia norkins

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