Moon boots and CAM walkers

What is a moon boot or CAM walker?

A controlled ankle motion (CAM) boot, often called a moon boot or walker, is a removable boot that supports and protects your foot and ankle after some injuries or surgery, while still letting you put weight on it¹. It works like a splint: a rigid sole held on with Velcro straps, and in some boots an inflatable liner for comfort and stability². The support lets you build up weight on the injured limb gradually as it heals³.

In healthy adults, a boot limits ankle movement, shifts pressure from the front of the foot towards the heel, and tends to slow walking⁴. It eases load on the forefoot but not the heel⁴. That was measured in healthy adults, so it shows how a boot changes walking, not how well it works for a particular injury.

What is it used for, and how well does it work?

The clearest benefit is for stable ankle fractures. Once a clinician has checked the break is stable, a removable boot or similar support is a sound choice⁵. In adults with a stable fracture of the outer ankle bone, walking in a boot early on seemed safe and gave better ankle function at 6 and 12 weeks than a below-knee cast⁶. After surgery to fix an ankle fracture, putting weight on the foot straight away in a boot gave better function at 6 weeks and an earlier return to work than a cast without weight, with similar complication rates⁷.

In toddler's fractures, a boot let children return to daily activities and weight-bearing sooner without affecting healing⁸. For a minimally displaced Jones fracture (a break on the outer edge of the foot) in adults, and for bone marrow swelling in the talus (an ankle bone), results were similar to a cast⁹¹⁰. How long full recovery takes isn't clear yet, so ask what to expect for your injury.

Is a moon boot right for me?

A boot suits injuries that are stable and haven't moved out of position, such as non-displaced breaks of the outer ankle bone, the shafts of the long foot bones, or the base of the fifth long foot bone on the outer edge of the foot¹. For an ankle fracture, ask whether it has been checked for stability, for example with x-rays taken while standing⁶.

A boot isn't usually used for ankle sprains, shin-bone fractures or toe fractures¹. Displaced fractures of the ankle, midfoot or heel need hospital care rather than a boot¹¹.

If you have diabetes, numb areas or frail skin, your skin needs extra checking¹². Tell your clinician about these, and about any earlier clots or circulation problems, before you get a boot.

What happens when I get a boot?

Your clinician will fit the boot and show you how to wear it. At home, sit with your knee bent at 90 degrees, put your heel right to the back with your foot flat, fasten the liner snugly, then fasten the straps from your toes upward until firm but not tight¹³. If it has air cells, pump them until comfortable, and let the air out before taking it off¹³¹⁴. Stand to check the fit: your toes shouldn't stick out past the edge, and the top back edge shouldn't press into the back of your knee¹. If it feels tight, loosen a strap².

Your clinician sets how long you wear it, which varies with the injury. Ask for a plan for coming out of the boot. Don't drive while wearing it³.

What are the risks and side effects?

Immobilisation and reduced movement raise the risk of a blood clot in the leg (deep vein thrombosis)³. Keeping active within your clinician's advice and drinking plenty of fluids can lower the risk¹².

A small number of high-risk people can get a pressure sore in a boot that severely limits movement, so reposition your leg regularly while resting, about every two hours³. Skin checks, including the heel, matter most with diabetes, frail skin or reduced feeling in the leg¹²¹⁵.

Pain in the knee on the same side, the opposite hip and the lower back is common with boot use⁴. Walk carefully on wet or slippery surfaces¹⁴. Poor fit can also strain the knee¹.

How does it compare with other options?

For stable ankle fractures, a removable boot can take the place of a cast. Supports ranging from rigid boots to elastic bandages all gave good function, so even light support may be enough for some stable fractures⁵. A short boot suits offloading the front of the foot better, while a tall boot limits ankle movement most⁴.

For diabetic foot ulcers on the sole of the foot, a guideline recommends a total contact cast (a close-fitting cast) or a walking boot that can't be removed, rather than a removable one¹⁶. If you have one, don't swap your prescribed device for a removable boot without advice from your foot team.

A removable boot only works if you wear it as directed. Ask why a boot, cast or brace was chosen for your injury.