Obesity and total ankle replacement: what the new study means for people with ankle osteoarthritis

Plain English summary of the study

A large US database study looked at people who had primary total ankle replacement, and split them by BMI. The headline finding was that people with BMI 40 or higher had more major medical complications within 90 days after surgery. Five year implant survival looked similar across weight groups, but the study did not have the power to rule out meaningful long term differences. In clinic we treat lots of active adults with ankle osteoarthritis and this paper helps frame the risks patients face if they are thinking about replacement surgery.

What we see

Patients with ankle osteoarthritis come to us with stiffness, pain across the joint line, and reduced activity tolerance. On the Central Coast that often means someone who can no longer run the beach paths, a parent worried their teen can't handle school sport, or a weekend netball player avoiding pivoting. Symptoms can overlap with plantar heel pain or plantar fasciitis when people unload the ankle and overload the heel. In practice we often see people blaming heel pain for reduced running, when the ankle joint is the main problem.

Why it's happening

Ankle osteoarthritis is usually post-traumatic or degenerative. The joint loses cartilage, motion becomes restricted, and compensations appear higher up or below the joint. That changes pressure and loading patterns through the foot. If someone walks with a guarded ankle they will shift load to the lateral forefoot and heel, which can provoke plantar fasciitis or running heel pain. When we talk about obesity and surgery, extra body mass increases whole-leg and foot loading, raises cardiometabolic strain during and after surgery, and can make wound healing and medical recovery harder.

What we test

We do clear, practical tests. Gait and pressure analysis tells us where load is going; in clinic we use a treadmill pressure system for a more objective look when the answer is unclear. Strength testing of ankle invertors and evertors is useful, as is calf and hip strength screening. On exam we check ankle range of motion, crepitus, and alignment. Imaging confirms joint space loss and subchondral changes. For someone considering total ankle replacement we also look at overall medical fitness, cardiorespiratory status, and factors that affect wound healing.

What actually changes it

Non-surgical steps often change symptoms and function enough to postpone or avoid surgery. Those include targeted load management, graduated strengthening to improve load tolerance, gait work to reduce harmful pressure patterns, shock-absorbing footwear, and customised orthotics when indicated. For runners we break down weekly load and address running technique and cadence, because small changes reduce peak joint forces and running heel pain. If surgery becomes the option, the new study is a reminder to optimise medical risks first: weight reduction, smoking cessation, blood sugar control, and a staged plan with your orthopaedic surgeon for perioperative care.

How the study guides decisions

The paper shows people with BMI ≥40 have higher early postoperative complications after total ankle replacement. That does not mean surgery is off the table for everyone with higher BMI, but it does change the conversation. In clinic we explain three practical implications:

• Pre-surgery optimisation matters more. Even modest weight loss and improving cardiovascular fitness reduce surgical risk and speed recovery. That lowers the chance of those 90-day medical problems.
• Non-surgical care is not just a delay tactic. Strength, gait retraining, footwear and load management often restore activity for weeks to months. For some people this is enough to avoid the risks of major surgery.
• Shared decision making is essential. Five year implant survival looked similar overall in the study, but the authors could not exclude real long term differences for the very high BMI group. That uncertainty is part of the risk discussion before booking a replacement.

What people get wrong

People often assume ankle replacement is as straightforward as knee or hip replacement. The ankle is smaller, the forces through it are high, and recovery pathways differ. Another mistake is assuming heel pain means plantar fasciitis alone. We see runners labelled with plantar heel pain who still have limiting ankle osteoarthritis. Lastly, focusing only on the joint without addressing movement, load tolerance and strength is unlikely to produce durable results. Surgery without optimisation of load and medical factors increases the chance of early complications.

Practical next steps for patients on the Central Coast If you have ankle osteoarthritis and are active on the Central Coast, start with a focused assessment. In clinic we look at gait and pressure, test strength, and map loading patterns from the ankle down to the heel. For runners we review recent training, shoes, and running surfaces. For parents of sporty kids we assess growth-related contributors and coaching factors. If surgery is on the table we make a staged plan with the orthopaedic team that includes medical optimisation and a prehab strengthening program.

When to seek help sooner

See us promptly if ankle pain is rapidly limiting walking or sport, if you have recurrent wound or skin problems around the ankle, or if you have new systemic symptoms that could complicate surgery. If you are considering total ankle replacement and have BMI over 35, we suggest a discussion early so we can coordinate medical optimisation and realistic expectations.

Final practical note

If you also have plantar fasciitis or plantar heel pain, we treat those in parallel. Reducing harmful ankle compensations and improving load distribution often eases heel symptoms and reduces the need for invasive procedures. For running heel pain our focus is load, footwear, and progressive strengthening rather than quick fixes.