Unit 2 · The fat compartment system
The shape of an ageing face is decided in its fat compartments
The facial fat pads are the primary drivers of the visible ageing face. This unit takes the four compartments that matter most and asks, for each one, what it supports, how it fails and where the restoration belongs — which is very often not where the deficit is visible.
Framing
Superficial and deep are not two words for the same thing
Understanding compartment anatomy, the differences between superficial and deep compartments, and their differential ageing behaviour is essential to planning volume restoration at the correct anatomical level.
Superficial compartments sit above the SMAS and are the first to show visible atrophy and descent. Deep compartments sit beneath it and support the superficial compartments from below. Atrophy in a deep compartment causes subsidence of everything above it, which is why a deficit is frequently visible in one layer and caused in another.
Each compartment has its own blood supply, innervation and ageing trajectory, and each is bounded by retaining ligaments and fibrous septa. Those boundaries are what make the ageing face change shape rather than simply shrink: tissue does not migrate freely across a compartment border, so the transitions between full and empty become visible as lines and steps.
Learn · Deep medial cheek fat
DMCF — the compartment that fails early and quietly
The DMCF lies deep to the orbicularis oculi, between the zygomaticus major and levator labii superioris muscles, directly overlying the maxilla. It is one of the earliest deep compartments to atrophy with age, and its volume loss directly subsides the medial cheek and contributes to tear trough and nasolabial fold deepening.
Volume restoration at the supraperiosteal plane in this compartment supports the overlying superficial fat and provides structural lift. The compartment being deep is precisely why restoring it lifts rather than fills.
The deep medial cheek fat compartment lies:
Select an option to commit. The reasoning appears afterwards.
The DMCF lies deep to the orbicularis oculi, between the zygomaticus major and levator labii superioris, directly on the maxilla. It is one of the earliest deep compartments to atrophy, and it supports the overlying superficial cheek fat.
That support relationship is what makes it a high-priority restoration target. Restoring the DMCF at the supraperiosteal plane elevates the compartments above it. The visible improvement appears in the medial cheek and the fold, in a plane you never entered.
Learn · SOOF
Suborbicularis oculi fat and the tear trough complex
The SOOF lies beneath the orbicularis oculi in the lower periorbital area. Its atrophy contributes to malar descent and the hollowing associated with the tear trough complex.
The SOOF has a superficial and a deep component. Addressing the appropriate sub-layer is critical to safe periorbital volume restoration — the periorbital area does not forgive a plane that is approximately right.
Learn · Nasolabial
A fold is not simply ptotic tissue
The nasolabial fat sits anterior to the nasolabial fold and descends with age, deepening the fold.
A patient points at her nasolabial fold and asks you to fill it. The tissue anterior to the fold has clearly descended, so filling the crease looks like the obvious answer. Why is injecting directly into the fold rarely the correct approach?
Hold your answer before you open this. The value is in having committed to a mechanism first.
The fold itself is an anatomical structure defined by a dermal ligament — the nasolabial ligament — not simply a fold of ptotic tissue. The ligament tethers the skin, so the crease does not lift when the tissue beside it is inflated.
Volume restoration medial or deep to the nasolabial compartment supports and elevates the fold, whereas superficial injection directly into it risks visual worsening. The restoration goes where the support was lost, not where the line is.
A patient presents with a well-established nasolabial fold. Deep medial cheek support is clearly reduced. The approach most consistent with the anatomy is:
Select an option to commit. The reasoning appears afterwards.
The nasolabial fold is defined by the nasolabial ligament, a dermal structure, and its deepening is driven by descent of the nasolabial fat together with loss of DMCF support beneath it. Restoration medial and deep to the compartment re-establishes the support the fold has lost.
The general rule this illustrates is that the site of the deficit and the site of the treatment are frequently different. Direct intranasolabial injection is rarely the correct approach, and a fold that has been filled rather than supported reads as heaviness rather than as correction.
Learn · Jowl
The lower face compartment that appears to grow
The jowl compartment is the primary driver of lower face ageing. It enlarges with age — a combination of true hypertrophy and relative descent as supporting ligaments weaken — and descends inferior to the mandibular border.
A patient in her fifties has visible jowling and has been told elsewhere that she has “too much fat” along the jawline. She is not overweight and her lower face was slim a decade ago. What is she actually looking at?
Hold your answer before you open this. The value is in having committed to a mechanism first.
The appearance of jowling does not necessarily indicate excess fat. It often represents the relative descent of cheek tissue exposing the mandibular margin.
This changes where the treatment goes. Volume restoration in the posterior cheek and above the pre-jowl sulcus can lift the jowl without treating it directly — and treating the jowl itself, on the assumption that it is a volume excess, addresses a problem the patient does not have.
A colleague proposes treating a moderate jowl by injecting the jowl compartment itself to smooth the mandibular border. Based on the compartment anatomy, the more defensible position is:
Select an option to commit. The reasoning appears afterwards.
The jowl compartment enlarges with age through true hypertrophy combined with relative descent as the supporting ligaments weaken. What the eye reads as new fat along the jawline is frequently cheek tissue that has moved, exposing the mandibular margin behind it.
The practical consequence is a restoration site well away from the visible problem. Support in the posterior cheek and above the pre-jowl sulcus lifts the jowl indirectly. Volume added into the jowl itself increases the weight of a compartment that has already descended.
Learn · Synthesis
The four compartments side by side
Read across the table rather than down it. The pattern that emerges — deficit visible in one place, support lost in another — is the working principle of this unit.
| Compartment | Position | Ageing behaviour | Restoration implication |
|---|---|---|---|
| Deep medial cheek fat | Deep to the orbicularis oculi, overlying the maxilla, between the zygomaticus major and levator labii superioris. | One of the earliest deep compartments to atrophy. Volume loss subsides the medial cheek. | Supraperiosteal restoration supports the overlying superficial fat and provides structural lift. |
| SOOF | Beneath the orbicularis oculi in the lower periorbital area, with a superficial and a deep component. | Atrophy contributes to malar descent and to the hollowing of the tear trough complex. | Sub-layer selection is critical to safe periorbital restoration. |
| Nasolabial fat | Anterior to the nasolabial fold, which is itself defined by the nasolabial ligament. | Descends with age, deepening the fold. The ligamentous component tethers the crease. | Restore medial or deep to the compartment. Superficial injection into the fold risks visual worsening. |
| Jowl fat | Lower face, descending inferior to the mandibular border. | Enlarges through hypertrophy and relative descent as supporting ligaments weaken. | Posterior cheek and pre-jowl restoration can lift the jowl without treating it directly. |
Unit 2 summary
Clinical takeaways
- Deep compartments support superficial ones. Atrophy in a deep compartment causes subsidence of everything above it, which is why the visible deficit and the causative deficit frequently sit in different layers.
- The DMCF fails early and lifts when restored. It lies deep to the orbicularis oculi on the maxilla. Supraperiosteal restoration there supports the overlying superficial fat rather than filling it.
- A nasolabial fold is a ligamentous structure, not a crease in loose tissue. Support it from medial and deep. Superficial injection into the fold itself risks visual worsening.
- Jowling is usually descent, not excess. The mandibular margin is being exposed by cheek tissue that has moved. Posterior cheek and pre-jowl support lifts it without adding weight to a compartment that has already descended.