Question

Describe the “screw home mechanism” and name one muscle and one joint critical to normal functioning of the screw home mechanism. Explain two treatment techniques that you could use to restore a malfunctioning “screw home mechanism.”

Describe how you would differentiate between the gluteus medius, gluteus maximus and tensor fascia lata muscles when testing the strength of these muscles. Describe what you might observe in an individual with grade 2+ gluteus medius weakness on their right side, while standing on their right leg.

A patient presents with foot and ankle pain. Explain the procedure that you would use and the tests you could use to determine a specific articular cause of this pain.

Answer 1

1 . Screw home mechanism

The "screw-home" mechanism,allows for full knee extension (movement that increases the angle between body parts) and flexion (movement that decrease angle between two body parts). It provides knee stability for standing upright,and also for rotation between the tibia and femur. This happens in between full extension (0 degrees) and 20 degrees of knee flexion. The tibia rotates internally during the swing phase (when foot is not in contact with the ground) and externally during the stance phase (when foot remains in contact with the ground). External rotation results in tightening of both cruciate ligaments, which locks the knee.The tibia is then in the position of maximal stability with respect to the femur.

2. Muscle and joint involved

One muscle critical to normal functioning of screw home mechanism is popliteus muscle. This muscle is used to unlock femur and tibia when walking, by rotating the femur on the tibia during the stance phase. In swing phase, the popliteus muscle medially rotates the tibia on the femur. It is also used when sitting down and standing up. It is the only muscle in the posterior (back) compartment of the lower leg that acts just on the knee and not on the ankle.

One joint critical to normal functioning of screw home mechanism is tibiofemoral joint

3. Gait restoration by physiotherapy is a good treatment option for restoring screw home mechanism.

4. Gluteus medius, gluteus maximus and tensor fascia lata muscles

Gluteus medius acts to abduct and medially rotate the hip.Maintaining single-leg stance is required during walking and running.While performing single leg squat, if the opposite hip of the leg that you are standing on drops, or if the knee of the leg you are standing on rotates inward, that indicates a weakness in the gluteus medius.

Gluteus maximus acts to extend and laterally rotate the hip joint.

The tensor fasciae latae works in together with gluteus medius and gluteus minimus muscles to abduct and medially rotate the femur.

5. Grade 2 plus gluteus medius weakness is a result of partial tear of muscle associated with incomplete loss of strength and flexibility. The abduction, extension, internal and external rotational movements of the hip are affected.

6. A patient presents with foot and ankle pain

The physical examination and gait analysis will be performed, followed by tests such as X-rays provides detailed pictures of dense structures of bones.