There are three particular movement habits in asana practice that either cause or indicate problems with the hips: These will be covered in detail in separate posts, to keep posts shorter
1. Allowing the hip to push out to the side and not maintaining a level pelvis in the horizontal plane – lateral pelvic tilt
2. Hinging from the hips when folding forwards from a standing position or returning to an upright stance from a forward fold.
3. Arching the back and maintaining anterior pelvic tilt in your movements
It’s common for yoga-practitioners to develop weak Gluteal muscles from these habits because there are many muscles in the hip area that can be used to create the same movements and the result is overuse of some muscles and weakness of others.
Weak Gluteal muscles cause instability of the Sacroiliac joint, because the muscle fibres of the Gluteus Maximus have attachments to the Sacroiliac ligaments down the length of the Sacrum. These muscles are further weakened and damaged through excessive stretching.
It’s important to remember that if specific movements and asanas are practiced with very little variation and no consideration is given to correcting habitual misalignments, muscle imbalances develop and quickly become painful. Sometimes professional treatment improves the pain but then the problems return because movement habits haven’t changed. The fastest way to resolve muscle-imbalance is with corrective exercises from someone who has assessed your movements and muscle strength but a long-term improvement depends on becoming aware of how you move and maintaining that awareness as you practice.
The process of reciprocal inhibition also creates weak hip muscles – please refer to Reciprocal Inhibition and Hips for an explanation of how hip muscles are weakened by particular asana sequences. ‘Yoga butt’ or Ischial Tendonitis is common in Ashtanga practice and is an example of reciprocal inhibition. An analysis of ‘yoga butt’ follows the posts on movement habits
Reading Sources:
Kendall, Mc Creary, Provance, 1993, Muscles, Testing and Function
De Franca, 1996, Pelvic Locomotor Dysfunction
Ellenbecker, De Carlo, DeRosa, 2009, Effective Functional Progressions in Sport Rehabilitation
Yoga Anatomy for the Perplexed 
Numbers 1 & 2 are clear but I’m not sure I know what you mean with #2. If not at the center crease, or hips, where else would we be hinging from in a forward bend?
I also wonder if its correct to suggest that its inherently bad to practice the same asana forms repeatedly without variation. This would certainly be true if the forms, or how they are being practiced, are unsound but if we are only doing foundational poses and functional body movements in an appropriate way, isn’t this good muscle memory that helps address not so healthy muscle memory?
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You are quite right that there’s no other place to hinge from in a forward bend, however there are different ways to do this. I will go into more detail later, I didn’t think that people would read a 1 500+ word post.
Our bodies always follow an efficiency principle. We use the least number of muscles possible to create movements and any repetitive movements create familiar neural pathways and habits, which the body utilises as an unconscious motor pattern. It is well documented in sports medicine that repetitive movements are the starting-point for injury, which is why cross-training is advocated for sports. If you are practising strenuous yoga like Ashtanga, Forrest, Poweryoga, etc. the same applies.
Functional body movements are less problematic but the ratios in which asanas are practiced are important too. It’s not uncommon to encounter yoga teachers who present 90-minute classes consisting mainly of standing postures, with maybe a little bit of abdominal strengthening on the side. These teachers also tend to have hip problems and lower-back pain, or cause it in their students. A balanced practice incorporates many different types of asanas and movements and has a larger focus on core body strength than leg strength.
I consider muscle balance to be the overriding factor in muscle memory – our minds talk to our muscles, but muscles talk to each other and how muscles are utilised is determined by the strength-balances between the muscles that are acting to produce a particular movement. Strength imbalances are created by repetitive movements, amongst other things.
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