Bring everything down to one reachable level
In old age a guinea pig's back and hind legs stiffen, her grip weakens, and a ramp she once scampered up becomes a reason to stay at the bottom and miss food or water placed above. The kindest adaptation is to retire the upper storey as living space and arrange the whole home on the ground floor. If you keep a slope at all, make it long, shallow, covered in a grippy fleece surface, and edged so a wobbly pig cannot slide off the side.
Place the essentials within a few steps of her favourite hide: hay piled loosely at floor level so she can eat without pulling at a high rack, pellets in a heavy low dish she cannot tip, vegetables in the same familiar corner, and water in both a bottle mounted lower than before and a shallow stable bowl as a backup if neck movement has become sore. An older pig who has to choose between resting and walking to drink will often drink too little.
Make the floor kind to sore feet and joints
Bare plastic and thin bedding over a hard base are unforgiving to arthritic feet and can contribute to sore hocks. Lay a non-slip liner first, then a deep layer of fleece bedding or soft paper bedding that stays dry on top and cushions every step. Fleece needs changing and washing more often for a senior pig who moves less and sits longer in one damp patch, so keep spare liners ready rather than stretching a set an extra day.
Remove wire floors and wire shelves entirely if your cage has them, and check that hide entrances are wide and low enough for a rounder, stiffer body to enter without squeezing or stepping up. A cardboard or wooden hide with two openings is often easier than a small plastic house with one high lip.
Shorten distances and remove daily obstacles
Watch how your guinea pig actually moves before you rearrange, then build the layout around that route. Put a second hay pile and a second hide at the opposite end only if she still patrols happily; if she has stopped visiting the far end, that space is wasted and the food at that end is effectively missing. Scatter feeding, which delights a young pig, can frustrate an old one who cannot hunt for pieces, so keep most food predictable and in the open.
Keep handling areas calm and close. Nail trims, weight checks, and health looks are easier on her if a familiar fleece pad comes with her, and a low-sided carrier left in the cage as an extra hide means a vet trip starts from a place she already trusts rather than a chase around the pen.
Notice the changes this new layout should reveal
An adapted cage should make eating, drinking, toileting, and resting visibly easier within days. If she still avoids the bottle, loses weight, develops wetness or sores underneath, has overgrown teeth because hay intake has dropped, or stops moving to her toilet corner, those are signs the problem is pain or illness rather than layout alone, and a veterinarian who knows guinea pigs should see her promptly.
To keep the new routine steady when more than one person helps, KinsLe's Care Teams lets you assign the morning fleece change, the evening weight-and-appetite check, and bottle refills for this guinea pig to named helpers, with each finished task marked by a timestamp so a missed mobility check never goes unnoticed.