Knee Replacement Technique — Melbourne

Quadriceps-Sparing Subvastus Knee Replacement

The subvastus approach is a way of reaching the knee joint during a knee replacement without cutting the quadriceps muscle. Because the muscle that straightens your leg is lifted rather than divided, there is nothing in the extensor mechanism that has to heal before you start using it.

How It Differs From the Standard Approach

Every knee replacement is performed through an incision at the front of the knee, and the kneecap has to be moved aside to expose the joint surfaces.

  • Medial parapatellar (the traditional approach). The surgeon cuts through the quadriceps tendon and part of the vastus medialis obliquus (VMO) — the teardrop-shaped muscle on the inner side of your thigh just above the knee — then repairs it at the end of the operation.
  • Subvastus (quadriceps-sparing). The surgeon works underneath the VMO, lifting the muscle upwards and outwards while leaving its attachment to the kneecap completely intact. The arthrotomy is made below the muscle rather than through it, so no muscle is cut and none needs repairing.

Why the Quadriceps Matters

The quadriceps is the muscle you use to straighten your knee, stand up from a chair, climb stairs and control your leg going down them. After a traditional approach, part of it is healing at exactly the time you are being asked to use it.

Leaving it undivided is the reason the subvastus approach tends to allow earlier straight-leg raising and earlier confident walking — which is also why it fits well with our ERAS+ enhanced recovery pathway.

What the Evidence Shows

A 2023 systematic review and network meta-analysis of 33 randomised controlled trials compared surgical approaches for knee replacement. Compared with the standard medial parapatellar approach, the subvastus approach showed:

  • Better early range of motion — roughly 7–8° more knee bend in the first few days after surgery.
  • Less pain in the first week, on the order of one to two points on a ten-point scale.
  • Better early function scores on the Knee Society Score.

We think it is equally important to be clear about what the evidence does not show. The authors noted that the differences narrow as time passes. The advantage of a quadriceps-sparing approach is concentrated in the early recovery window — the first days and weeks — rather than in your knee at one or two years. By then, most patients do well regardless of which approach was used.

So this is a technique that can make the early part of your recovery easier and faster. It is not a reason to expect a fundamentally different knee in the long run.

Is It Suitable for Everyone?

No, and we will tell you honestly if it is not the right choice for your knee. The subvastus approach gives a smaller working window, and there are situations where a standard approach is safer or gives a better result:

  • Higher body weight or a heavily muscled thigh, where the soft tissues will not mobilise enough to expose the joint safely.
  • Significant stiffness, contracture or deformity that needs wider access to correct.
  • Revision surgery, where previous scar tissue usually makes this approach unsuitable.
  • Previous incisions that dictate where the new one must go.

Getting the implants in exactly the right position matters far more to the long-term result than which approach was used to put them there. If good exposure cannot be achieved safely, the right decision is to use a standard approach — and that decision is sometimes made during the operation.

How It Fits With the Rest of Your Care

  • Prehab before surgery, so you arrive with as much quadriceps strength as possible.
  • Multimodal, opioid-sparing pain relief so you are comfortable enough to move early.
  • Walking with a physiotherapist on the day of surgery under our ERAS+ pathway.
  • Objective re-testing at milestones through the Biomechanical Profile Assessment, so quadriceps recovery is measured rather than assumed.

Common Questions

Is this the same as minimally invasive surgery?
Not quite. “Minimally invasive” usually refers to a smaller skin incision. Quadriceps-sparing refers to what happens to the muscle underneath. A smaller scar with a divided quadriceps is not the same thing.

Will my scar be smaller?
Possibly, but that is not the point of it. The benefit is to the muscle, not the skin.

Does it change how long my knee replacement lasts?
No. Implant longevity depends on implant choice, positioning, your activity and your bone quality — not on the approach used to reach the joint.

Will I still need physiotherapy?
Yes. An easier start does not remove the need for structured rehabilitation; it lets you begin it sooner and with less pain.

Related Services & Information

Content reviewed by our knee surgery and physiotherapy teams. This information is general and does not replace personalised medical advice. Your surgeon will discuss which approach is most appropriate for your knee.