Having mobile and strong hips is crucial for athletic and functional movement. The hips move in six planes of motion. Loss of mobility or stability in any of these planes can cause movement compensations.
It will be difficult to maintain good technique for squatting, deadlifting, lunging, or any athletic activity without adequate hip function. The spine and the knees are usually punished for dysfunction at the hips due to compensations with how the body moves. Over time early wear and tear and degenerative changes may result at the hips or at the joints above and below.
Chronic sitting at work and school has predisposed many of us to hip stiffness due to inhibition of the glutes and adaptive shortening of hip flexors and hamstrings.
Fortunately there is much we can do to improve hip mobility and address weak and stiff muscles.
Using a foam roller can reduce some stiffness though the hip and thigh muscles. Some effective ways of rolling out stiffness can be seen below.
Bridge variations are great for activating the glutes and taking the hip flexors through a full range of motion.
Leg lowering and the active straight leg raise with core activation train the nervous system the coordinate the hips with the core and can normalize stiffness through the posterior chain muscles.
Using a mini-band with a moderate amount of resistance and pulling the hips though a full range of motion can normalize stiffness though the hip flexor muscles and take the glutes through a full range of motion.
The yoga pigeon pose effective at opening up the hips into external rotation. I think the contract-relax technique is effective here.
If your hips are not as mobile as they should be, try a few of these drills. This is a great place to start for improving hip function.