Lecture 12

Question 1

How does screw-home mechanism happen?

Answer 1

tibia or femur rotates during the last 30° of extension

popliteus assists in unlocking knee from terminal extension

Question 2

Why is the screw home mechanism important?

Answer 2

contributes to increased joint congruency/stability

Question 3

Closed chain screw home

Answer 3

femur rotates 10° internally in extension

Question 4

Open chain screw home

Answer 4

10° of tibial external rotation in extension

Question 5

Internal Torque

Answer 5

Highest at 45° of knee flexion
This is where the length-tension relationship is at its best ratio

Question 6

What should you keep in mind when doing quad exercises?

Answer 6

knee joint, puts stress on the knee which can cause injury

Question 7

Knee extension testing

Answer 7

unable to isolate different muscles with MMT
pt should stabilize with hands on table
can also stabilize thigh w/strap across table
knee at 15° of flexion

this angle allows us to find the weakness

Grade 3-5 = leg extended
Grade 2 = side-lying
Grade 0-1 = supine

Question 8

Knee flexion testing

Answer 8

hamstrings, sartorius, gracilis, popliteus, gastroc, plantar

prone w/knee flexed to 45°
stabilizing on thigh
watch for hip flexor or gastroc sub. Looks like dorsiflexion, creating passive tension

Question 9

Knee flexion testing, bias for med/lateral

Answer 9

Medial = force is down and outwards
Lateral = force is down and inwards

Question 10

Single Leg Bridge Test

Answer 10

heel on 40 cm box
knee in 30° flexion
>20 reps and symmetry

using screening for return to play, testing for endurance

Question 11

Chair Stand Tests

Answer 11

30 second sit to stand
start timer when pt starts
must stand up and then touch chair for full

Question 12

5 rep sit to stand

Answer 12

how fast can they complete 5 reps

Question 13

Single leg sit to stand

Answer 13

3 variations; max rep w/out stopping, 30s max rep, # of reps in 5s

Why should we use it? high inter-rater and test-retest reliability, cheap, easy to implement
MVIC very high compared to other exercises

Question 14

Step down test

Answer 14

6” step, hands on hips
pt must avoid hip drop, knee valgus, moving foot contacts step, hands come away from pelvis

pt fatigue, but a qualitative test vs a quantitative test

Question 15

External moment arm & open chain quad exercises

Answer 15

the external moment arm is the GREATEST at 0° of flexion/full extension. It decreases as flexion increases to 90°
100% of possible torque is produced at 0°of full extension

Question 16

External moment arm & closed chain quad exercises

Answer 16

the external moment arm is the GREATEST at 90 of flexion, it decreases as the person stands into 0° of flexion.

100% of possible torque is produced at 90°

Question 17

Best position for knees & quads

Answer 17

45° of flexion, in either open chain or closed chain

this produces 70% of torque, and not the full 100%

Question 18

How to reduce external torque on knee

Answer 18

load on the ankle during open chain extension, between 90-45° of flexion

rising from partial squat position, closed chain. Staying between 45°and 0°of flexion

Question 19

Internal torque knee

Answer 19

wants knee to EXTEND

quadriceps are at their strongest when the internal torque is the highest, which is 45-70°

Question 20

External torque knee

Answer 20

wants knee to FLEX

hamstrings are at their strongest when the external torque is the highest, which is 0°

Question 21

screw-home mechanism is determined by

Answer 21

shape of medial femoral condyle
passive tension in ACL
slight lateral pull of quads