Capacity and Best-Interests Decisions in Orthopaedic Practice

An 84-year-old woman with moderate dementia is admitted with a displaced intracapsular hip fracture. She is agitated, gives inconsistent answers, and at one point says she wants to go home. Her daughter says she would want the operation. The anaesthetist wants a decision by the morning.

This is not an unusual case. Some version of it happens every week in every trauma unit in the world, and it is handled correctly far less often than we would like to believe. The common failure is not cruelty or indifference — it is a set of shortcuts: assuming dementia means incapacity, asking the family to consent when they have no legal power to do so, or recording "lacks capacity" without ever documenting the assessment that produced that conclusion.

This post sets out how capacity is actually assessed, what "best interests" means in law rather than in casual usage, and how the frameworks differ by jurisdiction. It sits within our medico-legal series.

Three things that are true everywhere

Whatever the local statute, three principles are near-universal in the common-law world, and getting them wrong is the source of most errors.

Capacity is decision-specific. A person may lack capacity to manage their finances and retain capacity to decide about an operation, or vice versa. There is no such thing as a general finding that a patient "has no capacity". The question is always: capacity to make this decision.

Capacity is time-specific. It fluctuates — with delirium, sepsis, opioids, pain, time of day, and the presence of a familiar person. A patient who cannot engage at 3am may be entirely capable at 10am after their infection is treated and their analgesia is right. Where the decision can wait, it should wait for the patient's best moment.

Capacity is presumed. The burden is on the clinician to establish that it is absent, not on the patient to demonstrate that it is present.

The right to make an unwise decision

This is the principle surgeons breach most often, usually with the best intentions.

A patient is entitled to make a decision that you consider foolish, and doing so is not evidence of incapacity. The elderly man who declines fixation of his ankle fracture because he does not want to be in hospital, the woman who refuses amputation for a non-salvageable limb, the patient who chooses conservative management with a worse expected outcome — none of these refusals, by itself, tells you anything about capacity.

The distinction that matters is between the process of deciding and the content of the decision. Capacity assessment examines the process: can the patient take in the information, hold onto it, weigh it, and tell you what they have decided? It does not examine whether they reached the answer you would have reached.

The test in practice: if this patient had agreed with your recommendation, would you have questioned their capacity? If the honest answer is no, you are not assessing capacity — you are objecting to the outcome.

The assessment

The framework in England and Wales sits in the Mental Capacity Act 2005, whose structure has been widely copied and is a good general model. It sets five statutory principles:

1. Capacity is presumed unless established otherwise.
2. A person must be given all practicable support to decide before being treated as unable to.
3. An unwise decision does not by itself indicate incapacity.
4. Anything done for a person lacking capacity must be in their best interests.
5. It must be the least restrictive option for their rights and freedom.

Capacity itself is then assessed in two stages.

Stage one — is there an impairment of, or disturbance in the functioning of, the mind or brain? Dementia, delirium, intoxication, acute confusion, brain injury, severe pain or distress can all qualify. This stage is usually easy in a trauma setting.

Stage two — does that impairment mean the person is unable to make this particular decision at this time? A person is unable to decide if they cannot do any one of four things:

The third ability — using and weighing — is where genuine incapacity most often lies, and it is the one least often tested. A patient may repeat the risks back to you accurately and still be unable to apply them to themselves. Asking "what makes you want to do it that way?" reveals more than any number of comprehension checks.

Support first. Before concluding that someone cannot decide, you are obliged to try: treat the delirium, correct the pain, wait for the sepsis to settle, use their glasses and hearing aids, bring a family member who can help them communicate, use simple language and pictures, choose the right time of day, and use an interpreter where language is a barrier. A capacity assessment conducted at 3am on an untreated, undermedicated, deaf patient without their hearing aid is not an assessment.

Best interests is not "clinically optimal"

When a patient genuinely cannot decide, the decision passes to a best-interests process — and this is widely misunderstood as meaning "whatever gives the best clinical outcome". It does not.

A best-interests determination must consider:

• The person's past and present wishes and feelings, including anything written when they had capacity
• Their beliefs and values — religious, cultural, personal — that would have influenced the decision
• Any other factors they would have considered had they been able
• The views of family, carers, and anyone named by the patient or holding legal authority
• Whether the person may regain capacity, and whether the decision can wait until then
• The least restrictive option that meets the need

The decision-maker is the clinician proposing the treatment. Family members are consulted as an essential source of information about the person — but in most jurisdictions they do not consent on the patient's behalf unless they hold specific legal authority. "The daughter signed the consent form" is, in England and Wales, a legally meaningless act unless she holds a registered health and welfare Lasting Power of Attorney.

That distinction matters enormously in practice, because the conversation with the family changes shape. You are not asking their permission. You are asking them to help you understand what this person would have wanted — and you should say so, because it relieves them of a burden they should not be carrying.

Who can decide for someone else

An advance decision refusing a specific treatment, if valid and applicable to the circumstances, must be followed even where the clinical team believes the outcome will be poor. Overriding one is unlawful.

Emergencies

Where treatment is immediately necessary to save life or prevent serious deterioration and the patient cannot consent, treatment may be given without consent under the doctrine of necessity, limited to what is immediately required. This is a genuine exception and it is the right thing to do — but it is narrow. It does not extend to an elective procedure done during the same anaesthetic because it seemed convenient, and it does not authorise ignoring a known valid advance refusal.

How jurisdictions differ

The greatest divergence is in the standard the substitute decision-maker applies.

The US position is a genuine philosophical difference rather than a wording variation. Substituted judgment asks the surrogate to reconstruct the patient's own choice, even where that choice would not be objectively optimal. A best-interests standard asks what serves this person, with their wishes as a heavy input. In most real cases they converge — but where a patient held strong, clearly expressed views that cut against clinical advice, they can diverge sharply.

Australia is the trap for the unwary: capacity and guardianship law is state and territory legislation, so a surgeon working across jurisdictions is working under different statutes with different substitute decision-maker hierarchies.

Accurate as of July 2026. Capacity legislation is jurisdiction-specific and changes; confirm the framework applying where you practise.

The orthopaedic cases that recur

The hip fracture in dementia. By far the commonest. Note that surgery here is usually about pain control and the ability to be moved, not about restoring premorbid function — and framed that way, it is very often clearly in the patient's interests. Assess capacity properly rather than assuming; many patients with moderate dementia can meaningfully participate in a decision about pain.

The post-operative delirium refusing to mobilise or accept treatment. Capacity fluctuates hour to hour. Treat the delirium and reassess. Do not record a single 2am assessment as a settled finding.

The intoxicated trauma patient. Intoxication impairs capacity while it lasts. Where the decision can safely wait until they are sober, it should. Where it cannot, treat under necessity and document why waiting was not possible.

The patient refusing amputation for a non-salvageable limb. The hardest, and the one where the temptation to find incapacity is strongest. If they can understand, retain, weigh and communicate, the refusal stands however much it distresses the team. Get a second opinion, involve psychiatry if there is a genuine question, and document scrupulously — but do not manufacture incapacity to reach the outcome you want.

The adult with a learning disability. Capacity is presumed here exactly as anywhere else. The obligation to provide support to decide is at its strongest, and the assumption that a learning disability equals incapacity is both a clinical and a legal error.

For patients under the age of majority, competence is assessed differently again, and parental responsibility interacts with the young person's own decision-making — see Safeguarding for Orthopaedic Surgeons.

What to document

A capacity assessment that is not recorded did not happen. The note should show:

• The specific decision being assessed — not "capacity" in the abstract
• The impairment identified at stage one
• Each of the four abilities, with what the patient actually said, in their words
• The support provided before concluding incapacity — hearing aids, timing, family present, interpreter
• The conclusion, and that capacity may be regained
• For best interests: who was consulted, what is known of the person's wishes, beliefs and values, the options considered, and why the chosen option is the least restrictive

The single most valuable element is the patient's own words. "Asked why she preferred not to have the operation, she said 'I've had enough of hospitals and I want to be at home with my dog' — able to explain that without surgery the hip would remain painful and she would not walk again." That is a record showing weighing. A line reading "lacks capacity, family agree to proceed" is worth nothing to anyone, and it will not survive scrutiny.

See Defensible Clinical Documentation for the wider principles.

The summary

Presume capacity. Assess the decision in front of you, not the patient in general. Support them properly before concluding they cannot decide. Remember that disagreeing with you is not incapacity. If they genuinely cannot decide, ask what this person would have wanted rather than what would be clinically tidiest — and consult the family as informants, not as signatories.

And write down what the patient actually said. Everything else in the assessment is reconstruction; their words are evidence.

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This article describes legal frameworks for educational purposes and is not legal advice. Capacity legislation varies by jurisdiction — take advice from your indemnity provider or legal team on any specific case.