21st Lecture: Knee Flexion PDF

# 21^th lecture, Theoretical Part: Knee Flexion ## Objectives At the end of this lecture, the student will be able to: 1. Identify the primary muscles involved in knee flexion. 2. Identify the range of motion of knee flexion. 3. Describe the effect of weakness of knee flexion. 4. Descri...

# 21^th lecture, Theoretical Part: Knee Flexion ## Objectives At the end of this lecture, the student will be able to: 1. Identify the primary muscles involved in knee flexion. 2. Identify the range of motion of knee flexion. 3. Describe the effect of weakness of knee flexion. 4. Describe the effect of contracture of knee flexion. ## Content 1. Primary muscles involved in knee flexion. 2. Range of motion of knee flexion. 3. Effect of weakness of knee flexion. 4. Effect of contracture of knee flexion. ## Knee Flexion ### Primary Muscles: **Hamstring Muscle:** * **Lateral hamstring:** biceps femoris. * **Medial Hamstring:** Semimembranosus, and semitendinosus. ### Range of Motion: * The range of motion of complete flexion of the knee is of 0 to 120 - 130 degrees. ### Factors Limiting Motion: 1. Tension of Quadriceps muscles. 2. Contact of posterior aspect of thigh with calf muscle of lower leg. ## Anatomy of Biceps Femoris (Lateral Hamstring) ### Origin * **Long head:** upper inner quadrant of posterior surface of ischial tuberosity. * **Short head:** middle third of Linea aspera, lateral supracondylar ridge of femur. ### Insertion * Styloid process of head of fibula. * Lateral collateral ligament and lateral tibial condyle (Fig.1). ### Action * Flexes and laterally rotates knee. Long head extends hip. ### Nerve * **Long head:** tibial portion of sciatic nerve. * **Short head:** common peroneal portion of sciatic nerve. ## Anatomy of Semimemberanosus (Medial Hamstring) ### Origin * Upper outer quadrant of posterior surface of ischial tuberosity. ### Insertion * Medial condyle of tibia below articular margin, over popliteus and oblique popliteal ligament. (Fig.2) ### Action * Flexes fascia and medially rotates knee. * Extends hip. ### Nerve: * Tibial portion of sciatic nerve. ## Anatomy of Semitendinosus (Medial Hamstring) ### Origin: * Upper inner quadrant of posterior surface of ischial tuberosity. ### Insertion * Upper medial shaft of tibia below Gracilis (Fig.3). ### Action: * Flexes and medially rotates knee. * Extends hip. ### Nerve: * Tibial portion of sciatic nerve. ## Effects of weakness: * **a**. Weakness of both the medial and lateral hamstrings permits hyperextension of the knee. * **b**. Bilateral weakness leads to anterior tilting of the pelvis and the lumbar spine may assume a lordotic position (Fig 4). * **c**. Weakness of the lateral hamstrings causes a tendency toward loss of lateral stability of the knee, allowing a thrust in the direction of a bowleg position in weight bearing (Fig 5). * **d**. Weakness of the medial hamstrings decreases the medial stability of the knee joint and permits a knock-knee position, with a tendency toward lateral rotation of the leg on the femur (Fig 6). ## Effects of shortness or contracture: * **a**. Shortness of hamstrings causes Restriction of knee extension when the hip is flexed, or restriction of hip flexion when the knee is extended. * **b**. Contracture of both the medial and lateral hamstrings results in a position of knee flexion, and, if the contracture is extreme, it will be accompanied by a posterior tilting of the pelvis and a flattening of the lumbar spine (Fig 7). The document contains illustrations of muscle anatomy, with a focus on various aspects of the knee and its corresponding muscles. It also displays how different muscle imbalances result in various deviations of the lower limbs, for example: bowlegs, knock knees, lordosis.