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KneeSchool/Imaging Academy/Hamstring Tendons

Hamstring Tendons

Page 5.4.7 · Ultrasound of the Knee · imaging page

The medial hamstrings, which matter to a knee surgeon mostly because they are taken as graft.

Pipeline status. Editorial draft. Evidence verification did not run. Not consultant reviewed. Not for clinical use.

The same topic at 4 depths

Each tier deepens the one below it and never repeats it. Choose the level you want.

Hamstring Tendons

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For Medical Students

What It Shows

The medial hamstring tendons run behind the medial side of the knee to insert on the tibia, and the semitendinosus and gracilis are the two taken for grafting. 2.9.5 covers the semimembranosus anatomy.

Ultrasound shows them in short axis as small round structures that can be counted and traced. 5.2.8 covers reflection.

It matters because their presence, size and course bear on graft choice, and their absence after harvest is a recognised finding. 3.7.17 covers the hamstring graft biomechanics.

How It Is Acquired

Scan in short axis behind the medial knee, where the tendons are seen as separate round structures. 5.4.2 covers the medial knee.

Trace each tendon proximally and distally to identify it rather than assuming from position. 2.9.5 covers the semimembranosus anatomy.

Measure the cross sectional area where graft size is the question, which is the main pre-operative use. 3.7.17 covers the hamstring graft biomechanics.

Look for an accessory band or an aberrant insertion, which affects harvest. 2.9.7 covers the medial surgical anatomy.

After harvest, look for regeneration or absence, both of which occur. 5.9.7 covers post-operative medial reconstructions.

What Normal Looks Like

Separate round tendons of fibrillar texture in short axis. 5.5.10 covers the tendons.

A traceable course from the muscle bellies to the tibial insertion. 2.9.5 covers the semimembranosus anatomy.

A consistent cross sectional area along the tendon's length.

No fluid or thickening around the tendons. 5.5.12 covers the bursa.

What Abnormal Looks Like

An absent tendon after harvest, or a regenerated one of different texture. 5.9.7 covers post-operative medial reconstructions.

A small cross sectional area, which bears on graft adequacy. 3.7.17 covers the hamstring graft biomechanics.

An accessory band or aberrant insertion. 2.9.7 covers the medial surgical anatomy.

Peritendinous fluid or thickening at the insertion. 5.5.12 covers the bursa.

Key Learning Points

  • The semitendinosus and gracilis are the two taken for grafting.
  • They are seen in short axis as separate round structures.
  • Each tendon is identified by tracing rather than by position.
  • Cross sectional area bears on graft adequacy.
  • Absence and regeneration both occur after harvest.

MRCS Level

How It Is Acquired

In a viva this is the structure group to name when asked how graft size can be assessed before surgery.

The expected points are the short axis approach, the tracing, the cross sectional area, the accessory bands, and the post-harvest appearance.

Say that graft size can be estimated pre-operatively. 3.7.17 covers the hamstring graft biomechanics.

Say that an accessory band can cause a short harvest. 2.9.7 covers the medial surgical anatomy.

Say that a magnetic resonance study gives the same information alongside the rest of the knee. 5.5.1 covers the standard protocol.

What Abnormal Looks Like

The reasoning expected is that graft diameter relates to the tendon's cross sectional area and its length, so measuring the area is an estimate of the graft that can be made. 3.7.17 covers the hamstring graft biomechanics.

Graft diameter has been associated with failure, which is what makes a small tendon a pre-operative finding rather than an intra-operative surprise. 5.7.11 covers graft failure.

An accessory band tethers the tendon, so a stripper can transect it short, which is the mechanism behind a harvest that yields too little. 2.9.7 covers the medial surgical anatomy.

After harvest the tendon may regenerate with different tissue, which is why the post-operative appearance differs from both normal and absent. 5.9.7 covers post-operative medial reconstructions.

How Good It Is

Ultrasound measures these tendons quickly and is rarely used for it.

Its best contribution is a pre-operative cross sectional area in a patient where graft size is a concern, at no cost and no dose. 3.7.17 covers the hamstring graft biomechanics.

It is limited by the relationship between an area measurement and a final graft diameter not being exact, and by magnetic resonance imaging giving the same information within a study already being done. 5.5.1 covers the standard protocol.

No figures appear for accuracy on this page, under decision 028, and no cross sectional area or graft diameter values appear either: those are published quantities and this environment cannot check them.

Key Learning Points

  • Graft diameter relates to cross sectional area and length.
  • Graft diameter has been associated with failure.
  • An accessory band can cause a short harvest.
  • The tendon may regenerate with different tissue.
  • The same information usually comes within a magnetic resonance study.

FRCS Level

How Good It Is

At decision level this measurement matters in a narrow group of patients.

A small patient in whom graft diameter is a concern is the clearest case for a pre-operative assessment. 5.7.11 covers graft failure.

A revision where the ipsilateral hamstrings may have been harvested needs to know what is there. 5.7.14 covers revision cruciate imaging.

An accessory band identified pre-operatively changes the harvest technique, which is a Section 7 matter informed by this imaging. 2.9.7 covers the medial surgical anatomy.

In most patients the graft choice is made on other grounds and this adds nothing. 5.1.3 covers choosing the correct investigation.

Where It Misleads

The commonest error is assuming a tendon is present after a previous harvest. 5.9.7 covers post-operative medial reconstructions.

A tendon is identified by position rather than by tracing. 2.9.5 covers the semimembranosus anatomy.

A cross sectional area is converted to a graft diameter as though the relationship were exact. 3.7.17 covers the hamstring graft biomechanics.

A regenerated tendon is assumed to be equivalent to the original. 5.9.7 covers post-operative medial reconstructions.

The measurement is made where it changes nothing. 5.1.3 covers choosing the correct investigation.

Key Learning Points

  • A tendon is assumed present after a previous harvest.
  • A tendon is identified by position rather than by tracing.
  • An area is converted to a diameter as though the relationship were exact.
  • A regenerated tendon is assumed equivalent to the original.
  • The measurement is made where it changes nothing.

Fellowship Level

Where It Misleads

At fellowship level this is a cheap measurement with a narrow indication that is either ignored or over-applied.

Graft diameter's association with failure is reasonably established, and the step from a pre-operative tendon measurement to a final graft diameter involves the harvest, the folding and the preparation, none of which the imaging predicts. 5.7.11 covers graft failure.

That makes the measurement a screening tool for the patient at risk of an inadequate graft rather than a planning measurement, and the distinction is often lost. 3.7.17 covers the hamstring graft biomechanics.

Regeneration after harvest is well described and its mechanical contribution is not established, so a regenerated tendon's presence does not mean a second harvest is equivalent. 5.9.7 covers post-operative medial reconstructions.

Magnetic resonance imaging gives the same measurement inside a study that is usually already indicated, which makes a dedicated ultrasound hard to justify except where no magnetic resonance study is planned. 5.1.5 covers the cost effectiveness of imaging.

The reasonable position is to measure where graft adequacy is genuinely in doubt and to take the measurement from whichever study is already being done. 5.1.3 covers choosing the correct investigation.

Key Learning Points

  • The step from tendon measurement to graft diameter involves the harvest.
  • It is a screening tool rather than a planning measurement.
  • Regeneration is described and its mechanical contribution is not established.
  • Magnetic resonance imaging gives the same measurement within a planned study.
  • Measure where graft adequacy is genuinely in doubt.

Explore Further

Where this topic came from and where it goes next in the spiral.

References

No reference list is attached to this draft. Evidence verification has not run, because source retrieval was unavailable at generation time. Under the Operations Handbook a missing reference is acceptable and an invented one is a critical failure, so nothing has been cited and no citation marker appears in the text. This page carries no diagnostic accuracy figure, which is decision 028 rather than an omission: the comparative standing of the modalities is standard teaching and a specific sensitivity written from memory is the same class of claim as an invented citation, so ACC-001 refuses the number and the page states the comparison. A reviewer with the literature can add the figures into How Good It Is without restructuring the page. Any measurement here, including a sequence parameter, an angle or a millimetre, is written from standard teaching, has not been checked, and is registered under decision 006 in pipeline/config/figures with a verification state of UNVERIFIED_FROM_MEMORY.

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