Surgical Approaches in TKR

Part of The Joint Replacement Guide — Phase 4: The Operation · Article 24 of 44 · Knee

Key Points

  • The medial parapatellar approach is the most commonly used and best-established way of exposing the knee during total knee replacement.
  • Quadriceps-sparing alternatives, including subvastus and midvastus approaches, may provide modest advantages during early recovery in selected patients.
  • More restricted exposure can make these alternative approaches technically demanding, particularly in a stiff knee or where there is substantial deformity.
  • Differences in pain, strength and function generally become smaller over time.
  • The surgeon must use an approach that provides sufficient visibility to position the implants and balance the knee safely and accurately.

What Is the Surgical Approach?

The surgical approach describes how the surgeon opens the tissues at the front of the knee to reach the joint.

Most knee replacements use a skin incision running down the front of the knee. Beneath the skin, the surgeon makes a deeper opening called an arthrotomy. Different approaches principally vary in how this arthrotomy relates to the quadriceps tendon, the vastus medialis muscle and the kneecap.

A smaller skin incision does not necessarily mean that less work has been performed inside the joint. The important consideration is whether the chosen approach permits the operation to be performed accurately without unnecessary damage to the surrounding tissues.

Medial Parapatellar Approach

The medial parapatellar approach is the standard and most widely used exposure for total knee replacement.

The deeper opening runs through the medial part of the quadriceps tendon, continues along the inner border of the kneecap and then extends beside the patellar tendon. This allows the kneecap to be moved to the side, giving the surgeon a clear view of the joint.

Its advantages include:

  • broad and familiar exposure of the knee;
  • access to both the femur and tibia;
  • the ability to assess and balance the ligaments;
  • good visualisation of kneecap tracking;
  • adaptability if more exposure is required; and
  • suitability for a wide range of deformities and complex cases.

The approach does temporarily disrupt part of the quadriceps mechanism, which must be closed carefully at the end of the operation. Nevertheless, it has a long clinical track record and remains the reference approach against which most alternatives are compared.

Subvastus Approach

The subvastus approach passes beneath the vastus medialis—the inner part of the quadriceps muscle—rather than cutting through the quadriceps tendon.

Its aim is to preserve continuity of the quadriceps mechanism and the blood supply around the kneecap. Studies suggest that it may allow an earlier straight-leg raise, slightly less pain and somewhat better movement during the first days or weeks after surgery.[1,2]

These advantages are generally modest and do not consistently produce better long-term function. A large review of randomised trials found no meaningful difference between the subvastus and medial parapatellar approaches at one year.[1]

The subvastus approach can provide more restricted exposure. It may be technically difficult in patients with a very stiff or muscular knee, substantial deformity, previous surgery or anatomy that makes it difficult to move the kneecap safely. Body size alone is not an absolute reason that the approach cannot be used, but it may affect its technical difficulty.

Midvastus Approach

The midvastus approach is another quadriceps-preserving modification. It avoids extending the opening into the main quadriceps tendon but splits a limited distance through the fibres of the vastus medialis muscle.

It is therefore more accurate to describe the approach as quadriceps-sparing than completely muscle-sparing.

The midvastus approach may provide more exposure than a subvastus approach while preserving more of the quadriceps tendon than a conventional medial parapatellar arthrotomy. Some studies report small early improvements in pain, kneecap movement or quadriceps recovery. Longer-term outcomes are generally similar to those obtained through the medial parapatellar approach.[2,3]

Potential concerns include injury to muscle fibres or their nerve supply if the split is extended too far. The technique must therefore be performed carefully and within an exposure familiar to the surgeon.

Minimally Invasive and Quadriceps-Sparing Techniques

Some knee replacements are described as “minimally invasive” or “quadriceps-sparing.” These terms can refer to several different techniques and do not guarantee a particular result.

A shorter incision and reduced disturbance of the quadriceps may support early recovery. However, restricting the exposure too much can make it more difficult to:

  • identify the relevant bony landmarks;
  • make accurate bone cuts;
  • position the components;
  • remove cement or loose fragments;
  • balance the ligaments; and
  • assess kneecap tracking.

Some systematic reviews have raised concern about a greater number of alignment or component-positioning outliers with highly restricted quadriceps-sparing techniques, particularly during the surgeon’s learning curve.[4,5] Other reviews have not found a clear increase, so the evidence is not entirely consistent.

The incision should be long enough, and the exposure broad enough, to perform the replacement accurately and without placing excessive force on the skin, muscles, tendons or bone.

Other Approaches

A lateral parapatellar approach can occasionally be used, particularly for selected knees with a marked knock-kneed, or valgus, deformity. It approaches the joint from the outer side and may help address tight tissues in that part of the knee.

More extensive approaches may be required during revision surgery or in a very stiff or severely deformed knee. These are selected according to the individual operation and are not routine alternatives for most straightforward primary knee replacements.

What Actually Matters Most?

No approach can compensate for inaccurate bone preparation, inappropriate implant positioning or inadequate ligament balance.

A successful knee replacement depends on several connected elements:

  • adequate surgical exposure;
  • accurate positioning and rotation of the components;
  • appropriate restoration of overall alignment;
  • balanced ligaments throughout movement;
  • stable and smooth kneecap tracking;
  • secure fixation;
  • careful handling and closure of the soft tissues; and
  • effective rehabilitation.

The importance of these factors does not mean that every knee must be reconstructed to identical measurements. Different alignment philosophies exist, and surgeons may aim to reproduce aspects of a patient’s individual anatomy. Whatever philosophy is used, the components must be positioned deliberately and the knee must remain stable and well balanced.

The Importance of Surgeon Experience

The medial parapatellar approach remains widely used because it is versatile, reproducible and can be extended when necessary.

A subvastus or midvastus approach may be reasonable where the patient is suitable and the surgeon has appropriate experience with it. Any possible early-recovery benefit must be balanced against the need for dependable visualisation.

It is therefore reasonable for a surgeon to recommend their established approach rather than use an unfamiliar technique solely because it is described as muscle-sparing or minimally invasive. If adequate exposure cannot be obtained through the intended approach, extending or changing the arthrotomy during surgery may be the safest option.

Questions You May Wish to Ask

  • Which surgical approach do you normally use for knee replacement?
  • Why is that approach appropriate for my knee?
  • Does my stiffness, deformity or previous surgery affect the choice?
  • Are there meaningful differences in recovery or risk for me?
  • What would happen if more exposure were required during the operation?
  • How will you assess ligament balance and kneecap tracking?

In More Depth

Research suggests that the subvastus approach may improve the time taken to regain an active straight-leg raise by approximately one to two days and may slightly reduce pain during the earliest part of recovery.[1] More recent analyses similarly suggest early benefits from some subvastus techniques, while finding that the differences reduce as recovery progresses.[2]

These findings should be kept in perspective. Early improvements do not necessarily translate into better implant survival, greater long-term movement or superior patient-reported outcomes. Enhanced-recovery pathways, pain control, preoperative strength and postoperative rehabilitation may also substantially influence how quickly a patient mobilises.

The best approach is therefore not necessarily the one with the smallest incision. It is the approach that allows the surgeon to complete the planned replacement accurately, balance the knee appropriately and protect the surrounding tissues.

This article provides general information and does not replace individual clinical advice. The appropriate surgical approach depends on your anatomy, deformity, previous surgery and the judgement and experience of your surgical team.

References

  1. Berstock JR, Murray JR, Whitehouse MR, Blom AW, Beswick AD. Medial subvastus versus the medial parapatellar approach for total knee replacement: a systematic review and meta-analysis of randomized controlled trials. EFORT Open Rev. 2018;3(3):78–84. doi: 10.1302/2058-5241.3.170030.
  2. Stubnya BG, Kocsis K, Váncsa S, et al. Subvastus approach supporting fast-track total knee arthroplasty over the medial parapatellar approach: a systematic review and network meta-analysis. J Arthroplasty. 2023;38(12):2750–2758. doi: 10.1016/j.arth.2023.06.004.
  3. Li T, Zhuang Q, Xiao K, Zhou L, Weng X. Comparison of the clinical and radiological outcomes following midvastus and medial parapatellar approaches for total knee arthroplasty: a meta-analysis. Chin Med J (Engl). 2014;127(16):2982–2990. PubMed PMID: 25131239.
  4. Kazarian GS, Siow MY, Chen AF, Deirmengian CA. Comparison of quadriceps-sparing and medial parapatellar approaches in total knee arthroplasty: a meta-analysis of randomized controlled trials. J Arthroplasty. 2018;33(1):277–283. doi: 10.1016/j.arth.2017.08.025.
  5. Yuan FZ, Wang SJ, Zhou ZX, et al. Malalignment and malposition of quadriceps-sparing approach in primary total knee arthroplasty: a systematic review and meta-analysis. J Orthop Surg Res. 2017;12:129. doi: 10.1186/s13018-017-0626-y.

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