Can more of your knee be kept intact?

Often, yes — but only when the damage is limited. In the knee, that usually means either a meniscus tear where some tissue can still be repaired, or arthritis clearly confined to one compartment, with the remaining structures still healthy enough to keep. These are selection-led decisions: the symptoms, scan findings and examination need to match, rather than surgery being a set of options that can simply be chosen.

• For the meniscus, repair aims to keep the knee’s cushioning tissue in place; partial meniscectomy trims only the torn part that is unlikely to heal. Current reviews generally favour preservation when a tear is repairable, although repair usually means longer rehabilitation and still carries a meaningful risk of failure.
• For arthritis in one compartment, partial knee replacement — also called unicompartmental knee replacement — resurfaces only that worn area and preserves the unaffected parts of the knee. It is considered when disease is truly localised, not widespread across the joint.
• Mako is different again: it is a robotic tool used during knee replacement, adding CT-based planning and haptic guidance. It may improve planning and implant positioning, but it does not create a new reason to have surgery or turn an unsuitable knee into a suitable one.

When a meniscus tear can be repaired

In meniscus surgery, the deciding issue is whether there is enough useful tissue left to save. AAOS guidance and review articles describe repair as most realistic when the torn piece can be brought back into place, the edges can be held together securely, and the meniscus is not too frayed or worn to heal. Tears closer to the capsular rim, where healing potential is better, and reducible longitudinal or some horizontal tears are more often repair-friendly than complex, unstable or heavily degenerative damage.

Selection is also broader than the old picture of a young athlete with a neat peripheral tear. Reviews from 2014 and 2019 note that some older active patients, and some tears that extend into relatively avascular zones, may still be considered for repair in the right knee. Age alone does not decide it. Knee stability, cartilage condition, activity demands, and the exact MRI and arthroscopy findings all matter when judging whether preservation is realistic.

That is why repair is usually preferred when it is feasible, not when it is forced. Recent reviews generally favour meniscal preservation when feasible, but repair still carries a real risk of re-tear or non-healing. In a meta-analysis of isolated medial meniscal repair in a stable knee, the overall failure rate was 26%. Partial meniscectomy therefore still has a place for symptomatic tears that cannot be repaired reliably.

When partial meniscectomy still makes sense

A 2014 evidence-based review places partial meniscectomy in a selective role: it is mainly used for symptomatic meniscal tears that are not amenable to repair. In practical terms, that often means an unstable flap or fragment is driving catching, locking, or persistent pain in the knee, and trimming the damaged portion is the more realistic option than trying to stitch poor-quality tissue back together. AAOS patient guidance also notes that partial meniscectomy typically allows immediate weight bearing, so early recovery is often quicker than after a repair that needs protection while it heals.

That earlier progress comes with a trade-off. The AAOS describes the meniscus as a shock absorber and stabilising structure in the knee, so removing tissue may reduce some of that protection. Reviews published in 2019 generally favour preserving the meniscus when a tear is repairable. Partial meniscectomy still has a valid place, but not as the default when salvageable tissue remains.

In older patients with degenerative tears, the 2014 review is especially relevant: if there are no clear mechanical symptoms, structured physiotherapy, activity modification and pain management often come before surgery. If symptoms persist, meniscectomy may still be considered later. The final decision is usually based on the whole knee picture — including tissue quality, cartilage wear, alignment, symptom pattern, and what arthroscopy shows — rather than MRI wording alone.

Who is a good candidate for partial knee replacement

Partial knee replacement is usually considered when painful end-stage osteoarthritis is confined to a single compartment of the knee rather than spread throughout the joint. In the 2023 BASK/EKS consensus, unicompartmental knee arthroplasty was supported as an alternative to total knee arthroplasty for patients who meet those indications. The key point is fit: this is a compartment-preserving operation for a specific pattern of arthritis, not a smaller version of a total knee done for the same problem.

AAOS guidance and review articles describe the rest of the knee as needing to be in reasonable condition, with healthy bone, cartilage and ligaments preserved outside the worn compartment. A functionally stable knee still matters. Classic selection often favours an intact ACL, with the lateral and patellofemoral compartments functioning well, although the literature also notes that some ACL-deficient knees may still be considered in selected circumstances. Reviews from 2016 and 2018 make clear that the exact thresholds for issues such as ACL status or wear elsewhere in the knee are not identical between surgeons or implant philosophies.

For the right patient, AAOS notes that UKR may bring quicker recovery, less early postoperative pain and less blood loss than TKR, partly because more of the native knee is left undisturbed. That possible upside should not be read as overall superiority. TKR remains the better match when arthritis is more extensive, whereas UKR is better matched to a narrower, well-defined problem when the indications are genuinely met.

What Mako changes if knee replacement is planned

If knee replacement is already planned, Mako changes the way the operation is mapped and carried out. Mako is Stryker’s robotic-assisted platform, not a robot that independently performs a UKR or TKR. Before surgery it uses a CT-based 3D plan; during the operation the surgeon can assess alignment and soft-tissue balance in real time, and the system’s “AccuStop” haptic boundaries help keep bone preparation and implant positioning within the planned limits.

The most consistent evidence so far is about precision rather than promises. In a 2020 systematic review of robotic-assisted total knee replacement, component placement was more accurate and radiographic alignment outliers were fewer than with conventional manual surgery. Some comparative studies also suggested better early function and less blood loss or postoperative drainage. Those findings may matter, but they do not mean every patient gets a better overall result simply because a robotic platform was used.

The present limit is fairly clear. That same 2020 review did not show a clear short- to mid-term advantage for robotic-assisted total knee replacement in survivorship, complication rate or operating time, and long-term patient benefit remains uncertain. In practical terms, Mako does not decide whether a knee needs a partial or total replacement; it may refine how an already appropriate operation is performed.

How the decision is made in clinic

In clinic, the decision starts with the symptom pattern. The history checks where the knee hurts, whether there is catching or locking, and which activities are limited. Examination then looks at swelling, alignment and stability. When arthritis is suspected, weight-bearing X-rays matter because any preserving operation has to match the painful part of the knee.

For meniscal symptoms, MRI helps judge whether tissue may be repairable, although the final call is sometimes made at arthroscopy. For replacement decisions, the 2023 BASK/EKS consensus and current reviews point elsewhere: UKR depends on confirming wear localised to one compartment, with the rest of the knee suitable to preserve. Occasional objective tools may add detail, but they sit behind clinical judgement. The practical rule is simple: repair a salvageable meniscus, trim only when repair is not realistic, use UKR when symptoms, examination and imaging all line up for localised arthritis, and treat Mako as a CT-based planning and haptic guidance tool once replacement is already indicated. For that assessment, Lincolnshire Knee is part of the MSK Doctors group and accepts patients without referral; booking is available at lincolnshireknee.co.uk.

1. [1] Consensus statement on unicompartmental knee replacement: A collaboration between BASK and EKS. (2023). https://doi.org/10.1016/j.knee.2023.03.015 https://doi.org/10.1016/j.knee.2023.03.015