Side sleepers and sore hips: what the top layer of a mattress has to do

Most adults sleep on their side for most of the night, and side sleeping is the position that asks the most of a mattress. All your weight goes through two narrow points, the shoulder and the hip, and if the mattress does not let them settle, they take the pressure all night. Here is what a mattress has to do for a side sleeper, and what to look for on the spec.

A note on the word "pain": a mattress can take pressure off a hip; it cannot treat what is wrong with it. If a hip hurts in the day as well as at night, or the pain is new, see a professional. This guide is about the bed.

What happens on your side

Lying on your side, the mattress has to do two opposite things at once. It has to give under the shoulder and hip, so they sink in and the spine stays level rather than bowing upward. And it has to hold under the waist and knees, so the middle does not sag. A mattress that only gives (too soft) lets the hip sink into a hammock. A mattress that only holds (too firm) leaves the hip and shoulder perched on the surface with all the weight on them, which is where the ache comes from.

The mistake most people make

Going firm. Firm sounds supportive. For a side sleeper it is the worst option, because nothing settles: the hip sits on top of the mattress with the whole side of the body pressing through it, and the waist is left unsupported. If you have sore hips and a firm mattress, that is very likely the pairing.

What pressure relief means

The comfort layer, the top few centimetres, has to be deep enough and soft enough for the hip and shoulder to sink into, while the layer beneath stays supportive. On a spec sheet that means:

• 4 to 6 cm of comfort layer, minimum. Less than 3 cm on a firm spring unit is a hard mattress with a cover.
• Memory foam of 55 kg/m³ or more, or latex. Memory foam is the classic pressure-relief material because it moulds; latex does it with more bounce and less heat. Low-density foam (under 50) feels good in a showroom and dishes within a couple of years, at exactly the point your hip lies.
• A medium to medium-firm feel overall, around 5 to 7 on a ten-point scale. Softer than a back or front sleeper would choose.

Zoning helps more here than anywhere

A zoned spring unit, firmer under the hips and softer under the shoulders, is built for the side sleeper's shape. The shoulder settles, the hip is held from sinking too far, the waist is supported between them. See zoned springs explained. If you sleep on your side and you are choosing between two similar mattresses, take the zoned one.

The rest of the bed

• A pillow that fills the gap between ear and shoulder, so the neck is level. Side sleepers need a thicker pillow than back sleepers.
• A pillow between the knees keeps the top hip from rolling forward and twisting the lower back. Cheap and effective.
• The base: slats no more than 7 cm apart, or the mattress dips between them.
• Age: a mattress with a dip where you lie will hurt a hip regardless of what it is made of. Check for a hollow with the bedding off.

Heavier side sleepers

Over about sixteen stone, the comfort layer needs to be denser (60 kg/m³ and up) and deeper, and the support underneath firmer (Firm tension), so the hip sinks into the comfort layer rather than through it.

How we built ours

The Bad Back Years is a side sleeper's mattress: 5 cm of 60 kg/m³ memory foam on top for the hip and shoulder to settle into, over a 2,000-spring unit in five zones with a firmer centre third to hold the hips level, in Medium or Firm tension. For someone who sleeps hot, The Hot Flush does the same job with latex.

The short version

• Side sleepers need give at the shoulder and hip and hold at the waist.
• Firm is the wrong answer; medium to medium-firm with a real comfort layer is right.
• 4 to 6 cm of memory foam at 55 kg/m³ or more, or latex; zoned springs beneath.
• Knee pillow, thicker head pillow, sound base.
• A mattress relieves pressure; it does not treat a hip.