Health insurance vs healthcare trusts: How MSK costs actually behave

The effects of MSK are difficult to predict for healthcare scheme specialists, but even more so for others in the health and wellbeing ecosystem.

With employer healthcare cost inflation still running high, a recurring question is how musculoskeletal (MSK) is specifically affecting clients depending on the healthcare system they have in place, whether that’s a health plan, full PMI or a health trust.

Recent market data shows that employer medical trend remains elevated, with Aon projecting global trend at 9.8% in 2026 and Europe at 8.2%, while Mercer Marsh Benefits forecasts 11.1% globally excluding the US.

In the UK, “full PMI” and a “healthcare trust” can look very similar to employees. They may involve the same hospitals, the same consultants and the same physiotherapy networks. Financially, though, they behave very differently for the employer - nowhere more so than in MSK.

That is because MSK is no longer a side issue in employer healthcare. Aon notes that MSK conditions have entered the top five drivers of medical plan costs in 2026, while Mercer Marsh Benefits reports that MSK is now the third highest cause of claims by frequency globally.

MSK is:

Very high frequency
Operationally messy
Highly sensitive to access and pathway design - particularly related to early or late intervention and acute or chronic issues

The effects can be difficult to predict for healthcare scheme specialists, but even more so for others in the health and wellbeing ecosystem.

While different conditions affect the two systems in different ways, in reality there are also broader, often unrelated scale and governance factors that determine which model works best for any given employer - that’s out of scope for this article.

Full PMI (insured)

With an insured PMI scheme, you pay a premium and the insurer carries the claims risk for that policy year, subject to the usual pooling and experience-rating mechanics.

That means your MSK cost is mostly smoothed into a predictable premium line.

You still influence the next renewal - utilisation, claims inflation, provider charges, and NHS access pressures all show up in the premium discussion - but day to day, a spike in MSK episodes doesn’t hit your profit and loss as a sudden cash event. It hits you at renewal.

This is why insured PMI is often the default for employers who value budget certainty and low governance burden. It’s also why, in years where MSK and mental health utilisation rises, employers can experience painful renewal uplifts.

Many employers with higher-utilisation workforces are already reporting premium increases of 15-30% at renewal as MSK and chronic condition claims compound year-on-year, according to Lockton (2025)

Healthcare trusts (self-insured)

In a healthcare trust, the employer funds claims from a trust fund rather than paying a single insurance premium.

In practice:

You estimate an annual claims budget
Pay money into the trust
Claims are paid out as they arise

Most employers add protection (stop-loss) to cap exposure from large individual claims and/or total claims exceeding an agreed level. Once the agreed stop-loss limit is reached, further eligible claims are paid by the stop-loss insurer rather than the employer, with no change to the employee’s access to care.

You also pay administration costs and often still pay Insurance Premium Tax on the stop-loss element. It is a different structure from insured PMI, but it’s still a cost line many teams forget to model.

The key commercial difference is simple: in a trust, MSK demand hits cash flow directly.

Outside of health insurance models:

With many organisations facing difficult decisions around PMI affordability, some are actively considering alternative funding paths, while others are already operating with health or cash plans where those structures better fit workforce needs.

It’s worth noting that health and cash plans behave very differently again from both insured PMI and trusts. They typically provide defined, capped contributions toward care rather than underwriting clinical pathways. For MSK, that means they often support access to individual components of care (for example physiotherapy sessions) without controlling sequencing, escalation, or return-to-work integration.

The result isn’t inherently good or bad - but it does mean MSK demand, utilisation patterns, and downstream productivity impact sit even further outside the benefit design itself. In that context, understanding how MSK behaves operationally becomes more important, not less.

Why MSK behaves differently between the two

Frequency vs severity

MSK conditions are commonly one of the most frequently claimed-for areas in corporate medical schemes.

In an insured model, that volume is largely absorbed into premium pricing.
In a trust, that volume directly drives cash out of the fund month to month.

So two employers with identical MSK incidence can experience the pain very differently:

One sees it as an annual negotiation problem (premium)
The other sees it as an in-year budget management problem (claims fund burn rate)

Volatility

With MSK, it’s not unusual to see clustering effects:

New site opens
Big project hits peak intensity
Hybrid working patterns shift
Manager cohort is under stress
Workplace change drives more static working

In insured PMI, the insurer effectively smooths that volatility. It still reappears at renewal, but it doesn’t whipsaw monthly cash.

In a trust, if the MSK pathway isn’t designed tightly, a sharp run-rate increase can happen quickly - especially where access is frictionless and there’s no triage steering people to the right level of care.

Incentives

In insured PMI, you can absolutely drive value through MSK pathway design (triage, digital MSK, appropriate imaging rules, evidence-based rehabilitation, return-to-work integration).

But the savings can feel indirect, because they show up as “a better renewal outcome than it could have been” next year, which is hard to prove.

In a trust, the feedback loop is clearer: better MSK triage and prevention reduces claims paid from the fund, and any surplus remains available for future years rather than becoming insurer margin.

This is one reason trusts are often positioned as cost-effective and flexible for larger employers who can tolerate some risk and want more control.

The hidden MSK costs don’t care about funding model

For MSK, the biggest costs often sit outside the medical plan entirely:

Absence
Presenteeism
Manager time
Employee churn
Workplace adjustments

Whether you’re insured or in a trust, while it can feel quite different - the truth is the costs are broadly in line. And if your MSK strategy is “we have PMI, so it’s covered”, those even larger productivity costs continue either way.

So what does this mean in practice?

If you want predictability and minimal governance, insured PMI keeps MSK as a renewal-cycle issue. You still need an MSK strategy, but the financial signal is muted and delayed.

If you want control and are willing to manage risk, a healthcare trust turns MSK into something you can actively influence.

Done well, it can be more efficient because you’re funding care rather than insurance margin.

Done poorly, it becomes a leaky bucket - lots of low-value physiotherapy, unnecessary imaging, slow return-to-work, and a claims fund that drifts upward month by month.

The consistent pattern across both models

Where employers tend to make progress (regardless of funding model) is when MSK is treated as a pathway, not a perk:

Early identification of risk (especially in desk-based populations where problems build quietly)
Fast access to the right first-line intervention
Clear escalation rules (complex cases move quickly; simple cases don’t get over-medicalised)
Integration with workplace factors:
- workstation set-up
- job design
- manager capability
- behaviour change That’s the gap.

The funding model changes where the cheque is written. It doesn’t change what actually drives MSK cost.