Meniscal Landmark Studies

FRCS Level

What the Question Was

The meniscal literature asks one question in four forms, and the forms were separated by decades.

Does removing a meniscus harm the knee. What does the meniscus do mechanically that explains the harm. How much of it can be removed before the harm begins. And does removing a torn fragment help the symptom it was removed for.

The first question was answered clinically before the second was answered mechanically, which is unusual and is why this chapter reads as a vindication rather than a discovery. 3.6.1 covers the functions.

What Was Done

Fairbank described the radiographic changes that follow meniscectomy from clinical series in the middle of the twentieth century, before any mechanical explanation existed.

Walker and Erkman measured load transmission through the tibiofemoral joint with and without the menisci in the 1970s, using cadaveric specimens and pressure sensitive methods.

Seedhom worked on meniscal load bearing in the same period, separating the proportion of load the menisci carry from the proportion the exposed cartilage carries.

Fukubayashi and Kurosawa quantified contact area and contact pressure in the 1980s, with the menisci intact and after removal, at a range of flexion angles.

Shrive and colleagues examined the circumferential fibre architecture and showed how hoop tension converts a compressive load into a circumferential one.

Arnoczky and Warren mapped the meniscal blood supply, which set the boundary between the repairable periphery and the avascular inner zone.

Thorlund and colleagues, and separately Katz and colleagues, ran randomised trials in the 2010s comparing arthroscopic partial meniscectomy with physiotherapy or with a sham procedure in degenerate knees.

What It Showed

Removing a meniscus is followed by degenerative change, and the clinical observation came first and has never been overturned.

The menisci carry a substantial share of the load across the joint, and removing them concentrates that load onto a much smaller cartilage area.

Contact pressure rises sharply as contact area falls, which is the mechanical sentence the whole subject turns on. 3.5.5 covers the effect of meniscal loss.

The circumferential fibres are the load bearing architecture, which is why a radial tear that crosses them is mechanically different from a longitudinal tear that does not. 3.6.3 covers the fibres.

Only the peripheral zone has a blood supply, which explains both why peripheral tears can be repaired and why inner zone tears were resected for so long.

In a degenerate knee with mechanical symptoms, arthroscopic partial meniscectomy did not outperform physiotherapy or a sham procedure in those trials.

What It Changed

Meniscal preservation replaced meniscal resection as the default intention, and the shift is directly traceable to the contact pressure work.

Repair technique developed around the vascular boundary rather than around the tear pattern alone.

Root repair became a recognised procedure once extrusion and hoop tension were understood as one mechanism. 3.6.9 covers root biomechanics.

The randomised trials changed guidelines for degenerate tears and changed practice more slowly, which is worth stating plainly rather than treating as an aside.

Fellowship Level

What Was Done

The contact mechanics studies used pressure sensitive film or similar inserted methods, and inserting anything into a joint space changes the space.

Reported contact areas and pressures therefore carry a systematic method error that varies between laboratories, which is why absolute figures differ more than the direction of effect does.

The load bearing proportions come from static loading at selected flexion angles, not from walking, so they describe capacity rather than use.

The randomised trials recruited degenerate knees with mechanical symptoms, which is deliberate and also the single most important thing to know before quoting them.

What It Showed

Where the literature is strong: the direction and rough magnitude of the pressure rise after meniscal loss, reproduced across methods and laboratories.

Where it is weak: how much of a meniscus can be removed before the effect matters clinically. The mechanical work gives a continuous relationship and practice wants a threshold, and no threshold is well supported.

Where it is contested: whether the randomised trial findings extend to a younger patient with a traumatic tear and a mechanically obstructing fragment. The trials did not study that patient, and both sides of the argument use them as though they had.

Transplantation and substitution evidence is mechanically coherent and clinically thin, which is a different position from the resection literature. 3.6.14 covers it.

What to Read Now

Read a contact pressure figure for its direction and treat its absolute value as method dependent.

Check what population a meniscectomy trial recruited before applying it, and say so when quoting it.

Read the root and extrusion literature as one subject, since a root tear that does not extrude and an extrusion without a root tear behave differently.

Do not look for a safe resection threshold in this literature, because the relationship it describes is continuous.

Consultant Perspective

What It Changed

The decision this literature informs is whether to take a fragment out, and it is now one of the clearest balance arguments in knee surgery rather than a technical choice.

Arguing for resection: a mechanically obstructing fragment causes a symptom the patient can describe and locate, the operation reliably removes that fragment, and waiting has its own cost in function and confidence.

Arguing against: the contact pressure work says every millimetre removed is permanent and cumulative, the trials found no advantage in the degenerate knee, and the symptom that prompted referral often settles without surgery.

Weigh the patient's age and physiology, because the pressure argument has forty years to act in a thirty year old and ten in a seventy year old. Weigh comorbidities, since several of them change both the anaesthetic risk and the rehabilitation. Weigh the demands on the knee, because a locked knee in a roofer and a clicking knee in a swimmer are different problems. Weigh their psychological state, since a patient convinced the knee is damaged beyond use will not rehabilitate it. And elicit their ideas, concerns and expectations directly, because the commonest expectation brought to this consultation is that a scan finding must be fixed.

State the balance to the patient in those terms and record which way it fell.

What to Read Now

The teaching point this chapter carries better than any other in Section 3 is that mechanical evidence and trial evidence can agree and still take fifty years to change practice.

Read Fairbank's observation and the modern trials together, because the second is the first with a control group.

Be careful teaching the trials as a verdict on arthroscopy. They are a verdict on one procedure in one population, and treating them as broader than that is the mirror image of the error they corrected.