Which one fits your knee problem

The useful first split is not between operations, but between knee problems. These three procedures usually sit in different parts of the pathway.

• ACL reconstruction fits an unstable knee after an ACL tear. Its job is to restore stability with a graft, most often done arthroscopically, and the usual graft choices include patellar tendon, hamstring tendon and quadriceps tendon. In practice, this is the option considered when the dominant problem is the knee giving way rather than arthritic wear.
• Total knee replacement fits a badly worn arthritic knee. AAOS describes it as a treatment for knees that are severely damaged, most often by arthritis, when non-operative measures are no longer enough to control pain, stiffness and loss of function.
• High tibial osteotomy fits a one-sided overload pattern, most commonly medial compartment arthritis with varus alignment. The bone is realigned to shift load away from the damaged side, with the aim of preserving the joint and delaying replacement.

That means the real early decision is diagnostic: instability, end-stage arthritic wear, or unicompartment wear with malalignment. Age, activity level, alignment, the pattern seen on X-ray or MRI, and personal goals all matter. Long-term HTO data, for example, suggest outcomes are often strongest in younger patients with lower BMI, while knee replacement is the more definitive option once damage is severe and symptoms remain limiting despite appropriate non-surgical care.

How ACL graft choices differ

Among ACL grafts, the practical question is usually which trade-off matters most once surgery is over and rehab begins. AAOS lists patellar tendon, hamstring tendon and quadriceps tendon as established autograft options, and comparative studies do not show one option leading on every measure.

• Patellar tendon (BPTB) has the longest track record. In systematic reviews with roughly 9- to 10-year follow-up, some studies favoured it for activity level or instrumented laxity. Those same reviews did not show a significant difference in graft rupture compared with hamstring grafts, and several studies reported more anterior knee pain and kneeling pain after graft harvest from the front of the knee.
• Hamstring tendon remains widely used because its long-term results are broadly comparable to patellar tendon for failure and laxity, while donor-site symptoms may be easier for some patients to live with. That can matter in work or sport where repeated kneeling or pressure on the front of the knee is a regular part of the week.
• Quadriceps tendon has become more prominent in recent years. In a randomised trial of 51 primary ACL reconstructions, quadriceps and hamstring grafts produced similarly improved stability, strength and patient-reported scores at 2 years; return to pre-injury activity averaged about 82 days with quadriceps versus 95 days with hamstring, although the overall results were reported as comparable. Meta-analyses also suggest quadriceps grafts have comparable graft survival and knee stability to patellar and hamstring grafts, with lower donor-site morbidity than patellar tendon.

In practice, the final graft plan is usually shaped by the sport involved, the knee’s laxity profile, work and kneeling demands, tolerance of donor-site symptoms, associated knee pathology and surgeon experience.

What to expect in the first 6 weeks after knee replacement

For most patients, the first 6 weeks after total knee replacement are less about a dramatic leap and more about steady daily gains. Early rehabilitation commonly starts on the day of surgery or as soon as the patient is able, with ankle pumps, gentle knee bending and straightening, simple muscle activation and several short walks spread across the day. In its recovery guidance, AAOS describes early exercise and walking as repeated daily work, often in short sessions rather than one long effort.

The first 2 weeks are often the most hard-going. This stage is usually dominated by pain control, swelling, wound checks, getting safely in and out of bed or chairs, and re-establishing a regular walking pattern with a frame, crutches or sticks if needed. Progress can look quite ordinary at this point: a little more knee bend, a little straighter leg, and a little more confidence moving around the house from one day to the next.

From about week 2 to week 6, the emphasis commonly shifts towards better knee bend and straightening, longer walking tolerance, and more confidence on stairs. Many patients are reducing their reliance on a cane or walker by around 6 weeks, but that is not a fixed deadline. Strength work also tends to build gradually; resistance-based exercises often become more meaningful at roughly 4 to 6 weeks, depending on swelling, wound healing and physiotherapy progress. Even when the early phase is going well, recovery does not finish at week 6: sources such as Cleveland Clinic note that overall improvement after knee replacement can continue for many months, sometimes up to a year.

Who high tibial osteotomy is really for

A high tibial osteotomy tends to make sense when knee pain is mainly on the inner (medial) side and the leg is in varus alignment — the slightly bow-legged pattern that pushes extra load through that compartment. AAOS describes the operation as cutting and reshaping the tibia so weight shifts away from the worn side. In plain terms, it changes the line of force through the knee. That is why HTO is different from replacement: it aims to preserve the patient’s own joint surfaces rather than remove and resurface them.

In practice, the more plausible HTO candidate is often someone who is still relatively active and whose arthritis pattern is mainly one-compartment rather than spread widely across the knee. Long-term outcome data help refine that picture. In a 20-year series, better survivorship was linked with age under 55, BMI under 30, and less severe symptomatic disability. Those are best seen as tendencies, not hard cut-offs, but they help explain why HTO is often considered for patients who want to keep their native knee for longer and whose knee mechanics still look correctable.

Age alone, though, does not settle the question. A 2024 systematic review looking at advanced medial radiographic osteoarthritis still reported average 10-year survivorship of 74.6% after HTO in selected cases. That suggests the operation should not be reserved only for very early wear. The sharper dividing line is usually the pattern of disease: medial overload with malalignment is the classic fit, whereas a knee with more diffuse compartment damage is less likely to match what HTO is designed to do.

How HTO recovery differs from knee replacement

Recovery after high tibial osteotomy is usually paced by bone healing, not just by pain and swelling. AAOS notes that healing of the osteotomy takes about 6 weeks, and that is why the early phase can feel more protected than many patients expect. In practical terms, the knee may be moving reasonably well while walking is still being advanced cautiously, because weight-bearing often depends on the fixation, the size of the correction, and the surgeon’s protocol rather than on confidence alone.

A simple way to remember the difference is this:

• after HTO, the first 6 weeks often protect the cut bone, so full weight-bearing may be delayed and rehabilitation has to respect healing time
• after total knee replacement, mobilisation usually starts on day 0 or as soon as possible, with early walking and exercises pushed sooner because there is no osteotomy site to unite
• in both operations, physiotherapy matters, but the limiting factor is different: after HTO it is often the healing tibia; after knee replacement it is more often pain, swelling, movement, and rebuilding stamina

That does not make HTO a “worse” recovery; it makes it a different one. The trade-off is that a slower early phase may help preserve the native knee. By contrast, knee replacement often gets people moving earlier, yet overall improvement in pain, movement, and endurance still continues for many months, and Cleveland Clinic notes that recovery can extend up to a year.

What usually settles the decision

By the time a knee decision becomes clear, it is usually not because one operation sounds more impressive. It is because the problem fits one of three patterns: an unstable knee after ACL rupture, a globally worn arthritic knee, or a 'one-compartment' knee where malalignment is doing much of the damage.

• For suspected ACL reconstruction, the most useful questions are practical ones: does work involve kneeling, does sport involve cutting and pivoting, and have previous front-of-knee symptoms or hamstring problems already narrowed the tolerable graft options? AAOS lists patellar, hamstring and quadriceps autografts, and published comparisons show trade-offs rather than a single graft that suits every knee.
• For knee replacement, ask what the first 6 weeks will look like at home: stairs, walking aids, who is around on day 1, how physiotherapy is arranged, and when driving or work can be reviewed realistically. Early rehabilitation starts straight away, but the pace still varies.
• For HTO, ask whether pain and wear are truly confined to one side, whether varus alignment is a major driver, and whether preserving the native knee is worth a slower bone-healing recovery of about 6 weeks.

What settles it in the end is not imaging alone. A consultant-led knee assessment can test whether a 'one-compartment' story on X-ray matches the examination and alignment, then decide whether the right next step is more rehab, injection-based care, joint preservation, or replacement.

1. [1] High survivorship rate and good clinical outcomes after high tibial osteotomy in patients with radiological advanced medial knee osteoarthritis: A systematic review. (2024). https://doi.org/10.1007/s00402-024-05254-0 https://doi.org/10.1007/s00402-024-05254-0