What mechanical and proprioceptive structures are involved in quadriceps stretching? Why is it important for patella travel?

Objective

Ely's, Ober's, and modified Thomas' tests are widely used. Stretching the front thigh involves two layers of tissue: the rectus femoris and its overlying fascia lata (FL). However, to our knowledge, no biomechanical study has analyzed these tests. Therefore, this study tries to determine the structures affected during the stretching of the front thigh.

Methods

An observational study of the front thigh was conducted. The directions and intensities of the reaction forces were recorded. The patellar travel was used to determine the average coordinates of the stretched structures at hip level in the horizontal plane. The participants indicated the stretched area. The stretch of a patient with a complete tear of his left rectus femoris was recorded.

Results

The reaction force of the thigh was oriented at 33° (standard deviation [SD]: 6°) sideways and its intensity was 60 N m (SD: 19 N m). The centroid coordinates of all stretched structures were stable. The registered average external rotational torque of 6 N m (SD: 3.7 N m) could only be mediated by the FL. The stretched area indicated by the participants could be anywhere on the FL. The tolerated reaction force increased in the same way on the disinserted rectus femoris thigh and on the uninjured thigh.

Conclusion

Ober's, Modified Thomas', and Ely's tests are three potential means of assessing FL extensibility. A lateral patellar tilt may be triggered by the FL's reaction force to stretching. Stretch tolerance seems to be limited by the FL, the fascia profundis of the thigh.