- Approach
- Beneath vastus medialis, tendon not divided
- Extensor mechanism
- Left intact
- Straight leg raise
- Often possible earlier
- Implant
- Same components as any approach
- Suitability
- Not all knees; assessed individually
- Long-term outcome
- Equivalent to standard approach
The skin incision
Total knee replacement is performed through a single incision at the front of the knee, typically running from just above the kneecap to just below it. The exact length and position vary from patient to patient, depending on knee size, prior surgery or scarring, and the surgical technique being used.
Incisions are closed carefully with attention to healing and scar appearance, and are typically dressed with a specialised surgical dressing for the initial recovery period.
The surgical approach
Once the skin is opened, the surgeon needs a way through the soft tissue, mainly the quadriceps tendon and surrounding structures, to reach the joint itself. This is called the surgical approach. The main options are:
Medial parapatellar approach The most widely used and well-established approach. The joint capsule is opened along the inner (medial) side of the kneecap, allowing the kneecap to be moved aside to access the joint. It gives reliable, well-tested exposure and is suitable for the great majority of knee replacements, including more complex cases.
Subvastus approach A muscle-sparing technique that goes around, rather than through, the vastus medialis muscle (part of the quadriceps). It aims to preserve muscle function and may be associated with a faster return of quadriceps strength in suitable patients. It requires more mobile soft tissue to perform safely and isn't suitable for every knee, particularly larger or stiffer joints.
Midvastus approach A middle-ground technique that splits a small portion of the vastus medialis muscle rather than fully preserving or fully dividing it. Like the subvastus approach, it's muscle-sparing relative to the traditional medial parapatellar approach, with similar considerations around suitability.
How the approach is chosen
The choice of approach depends on factors including the patient's anatomy, the degree of deformity or stiffness present, whether it's a first-time or revision surgery, and the surgeon's assessment of what will give safe, reliable access for that specific knee. No single approach is correct for every patient or every surgeon, and reputable, well-supported outcomes have been achieved with each of the approaches described above.
A note on "minimally invasive" language
You may see the term "minimally invasive" used to describe some surgical approaches to knee replacement. This generally refers to techniques that limit disruption to the quadriceps muscle and tendon (such as the subvastus and midvastus approaches) rather than a dramatically smaller incision. The evidence on whether these techniques meaningfully change longer-term outcomes compared with the standard medial parapatellar approach is mixed, and suitability is assessed individually.
This article is general information and doesn't replace a consultation. The approach used in your surgery is a clinical decision based on your individual anatomy and circumstances.
Questions worth asking at your consultation
Every one of these is a fair question and none of them should be awkward to ask. Print them or bring them on your phone.
- Am I a good candidate for muscle-sparing total knee replacement, and what would make me a poor one?
- What are the alternatives, including doing nothing for now?
- How many of these do you perform in a year?
- What does the Australian registry say about the implant you would use for someone my age?
- What does a realistic result look like for me specifically, and what will I still not be able to do?
- What is your plan if it does not go well?
Frequently asked questions.
What does quadriceps-sparing actually mean?
That the quadriceps tendon is not cut to get into the knee. The subvastus approach passes beneath the vastus medialis muscle and lifts it, rather than dividing the tendon above the kneecap as the standard approach does.
Does it change the implant or the operation itself?
No. The implant, the bone cuts and the alignment plan are the same. Only the route into the joint changes.
Will I recover faster?
The published difference is in the first few weeks, most consistently an earlier return of the straight leg raise and less early pain. By three to six months the outcomes are equivalent to the standard approach.
Can everyone have a subvastus approach?
No. Exposure is more demanding in heavier or very muscular patients, in stiff knees and after previous surgery. Where it is not appropriate, a standard approach is used and the result is not compromised.
References.
- Liu HW, Gu WD, Xu NW, Sun JY. Surgical approaches in total knee arthroplasty: a meta-analysis comparing the midvastus and subvastus to the medial parapatellar approach. J Arthroplasty. 2014;29(12):2298-2304.
- Teng Y, Du W, Jiang J, et al. Subvastus versus medial parapatellar approach in total knee arthroplasty: meta-analysis. Orthopedics. 2012;35(12):e1722-e1731.
- Australian Orthopaedic Association National Joint Replacement Registry. Annual Report. Adelaide: AOA.
This page provides general information about a medical condition and a surgical procedure. It is not individual medical advice and does not replace consultation with a qualified practitioner. Outcomes vary between individuals and all surgery carries risk. A referral is needed for a consultation with Professor Daevyd Rodda; without one, you can start with the practice nurse practitioner, who can provide it.