Your hip is a weight-bearing joint, and all of your weight above the waistline has to be supported by your hips. Whenever you stand, walk, or run, the weight-bearing joints in your body are subjected to external forces (gravity, heel-strike shock, etc.) and the strain of repetitive motion. A runner, for example, takes an estimated 1500 strides per mile, and a force of 2-3 times the body's weight must be effectively absorbed through the lower extremities with each step. Also, the weight of the body is supported on just one limb through three-quarters of the gait (walking) cycle; during that time, the muscles in your hip must contract to keep your torso from falling to the opposite side.
Because it is a masterpiece of structural design, the human body can usually deal effectively with gravity and heel-strike shock if it is in good health and posturally stable. But if you have slight postural imbalances and/or misalignments, those forces can gradually cause a variety of painful conditions which may affect not only your hip, but anywhere from your knees to low back. Your healthcare professional can determine the cause of your discomfort and recommend treatment.

If both of my hips are doing the same work every day, why does one hurt and not the other?

If traumatic injury (falling on the hip, a car accident, being tackled in a football game, etc.) has been ruled out, and the pain seems to lessen or go away completely when you're resting or "off your feet," you may have a postural imbalance — a foot problem and/or a leg length inequality (LLI) — that could be the cause of your hip pain.

What would a foot problem have to do with hip pain?

The feet are the foundation of your body; they support everything above them, including the hips. Feet function something like the basement in a house: if the basement doesn't support the weight of the floors above it, stress cracks can appear in walls at any level. And feet that aren't properly aligned can contribute to stress pressure at the hip joint.
Your feet also help to protect you against heel-strike shock. Every time the heel of your foot hits the ground, a shock wave travels up through your body, all the way to your head. The healthier and more posturally stable your body is, the more likely this shock is either dissipated or absorbed safely. But if your feet are not in their correct functioning position at all times, more of this shock is allowed to move through the body to weaken other joints — including the hip.

How can my healthcare professional help me to get better?

Depending on the diagnosis of your condition, your healthcare professional has treatment programs to help restore your hip to normal function. Along with any determination of the need for rest or other therapies (ice, ultrasound, etc.), a three-step program is often indicated:
Mobilization of the affected joint(s) for proper alignment.
Exercise to build muscle strength and joint stability.
Use of foot orthotics to help restore foot stability and absorb heel-strike shock.
Strengthening hip muscles helps to stabilize the joint and lower the incidence of further serious injury.
Custom Orthotics are often popular in restoring structural and functional balance of the legs as you stand, walk, or run. Your Auckland Sports Medicine Podiatrist will select the orthotics best suited for you based on a variety of factors (lifestyle, health, age, weight, etc.).