Muscles can be synergists in one direction, and antagonists in another.
For example, the TLF abducts, flexes and internally rotates the hip. Whereas the Posterior Glute Med (PGM) abducts, extends and externally rotates the hip.
In hip abduction, these two muscles must work in synergy to maintain a neutral leg.
Dominance of the TFL will draw the leg into IR +/- Flexion
Dominance of the PGM will draw the leg into ER +/- Extension
Testing strength with the hip in ER and extension will challenge the PGM.
– A positive test would be if the patient flexed/IR’d the hip.
Testing strength with the leg in ER will challenge the TFL.
– A positive test would be if the patient extended/ER’d the hip.
NB: During gait, the leg will excessively IR on heel strike.
- Lateral shift or rotation of pelvis
- Asymmetrical height of iliac crest
- Observation of adductor notch
- Adducted hips or varus position
- Increased lateral IT groove
- Positive result on SLS test
- Trendelenburg sign or increased lateral pelvic shift during loading response in gait.