Mr Osman Riaz is a consultant knee surgeon and one of the highest-volume knee osteotomy surgeons in West Yorkshire. He leads the osteotomy and joint-preservation service at Calderdale & Huddersfield NHS Foundation Trust, receives regional referrals for complex deformity and combined ligament injuries, and sees private patients from across the UK at Spire Elland Hospital and The Huddersfield Hospital.
Osteotomy means realigning the bone. For the right patient it corrects the mechanical cause of knee pain, instability or early arthritis at its source — protecting your own joint instead of replacing it. Every complex case is planned in 3D on your own CT scan using patient-specific instrumentation (PSI), so the correction achieved in theatre matches the plan made at the desk.
40+
knee osteotomies a year — one of the highest-volume osteotomy practices in West Yorkshire
120
ACL reconstructions a year — realignment and ligament surgery under one roof
3D
every complex correction planned on your own CT scan with patient-specific guides
What is a knee osteotomy?
A knee osteotomy is a controlled, precise cut of the femur (thigh bone) or tibia (shin bone) that changes the alignment of the leg. If you are bow-legged (varus) or knock-kneed (valgus), your body weight is funnelled through one half of the knee. That overloaded compartment wears out first — and it is also why some ACL grafts stretch and fail. By shifting the weight-bearing line back to the correct position, an osteotomy unloads the damaged part of the joint, relieves pain, protects cartilage repair and ligament reconstruction, and can delay or avoid a knee replacement.
Osteotomy may be right for you if you have:
- Knee pain with bow legs or knock knees — arthritis limited to one side of the knee
- A failed or stretched ACL graft with high tibial slope or varus alignment
- Anterior knee pain or a dislocating kneecap linked to rotational (torsional) malalignment
- Cartilage or meniscus damage that needs the load taken off it to heal
- A wish to stay active — running, sport, manual work — which a knee replacement does not reliably allow
The osteotomies I perform
High tibial osteotomy (HTO)
The workhorse of knee realignment. A medial opening-wedge HTO corrects bow-legged (varus) alignment and unloads the inner compartment — for medial arthritis in the younger, active patient, and to protect ACL reconstruction, meniscus repair or cartilage regeneration. I routinely combine HTO with ACL reconstruction and meniscal surgery in a single operation.
Distal femoral osteotomy (DFO)
For knock-kneed (valgus) alignment overloading the outer compartment, the correction usually belongs in the femur. DFO unloads lateral compartment arthritis and protects lateral meniscus and cartilage surgery in the valgus knee.
Double-level osteotomy
Severe deformity often sits in both bones. Correcting only one would leave the joint line tilted, so the femur and tibia are corrected together in one operation — a double-level osteotomy. These are demanding corrections where 3D planning and patient-specific guides matter most.
Tibial slope osteotomy — including infratuberosity correction
The slope of the top of the tibia matters to the ACL: a posterior slope above about 12 degrees drives the tibia forward with every step and is a well-established risk factor for ACL graft rupture. In revision ACL surgery I correct high slope with an anterior closing-wedge slope-reducing osteotomy. Where appropriate I use the infratuberosity technique popularised by Prof Matthieu Ollivier’s group in Marseille — the wedge is taken below the tibial tuberosity, preserving patellar height and the extensor mechanism while the slope is corrected, and keeping the proximal tibia clear for revision ACL tunnels. Slope correction is frequently combined with single-stage revision ACL reconstruction and lateral extra-articular tenodesis (LET).
Derotational osteotomy
Some knees hurt because of twist, not tilt. Excessive femoral anteversion or tibial torsion makes the kneecap track badly, causing anterior knee pain and patellar instability that no amount of physiotherapy fixes. After a CT rotational profile confirms the torsion, a derotational osteotomy of the femur or tibia corrects the twist at its source — often transforming symptoms in young patients told they simply have “patellofemoral pain”.
Tibial tuberosity osteotomy (TTO)
For patellar instability and kneecap maltracking, the attachment of the patellar tendon can be moved to redirect the kneecap into its groove — usually combined with MPFL reconstruction. TTO also protects cartilage repair behind the kneecap by unloading the damaged facet.
Patient-specific instrumentation (PSI) — 3D-planned surgery
Complex corrections are planned on a CT scan of your own leg. I set the target alignment, slope and rotation on screen, rehearse the operation in software, and a patient-specific cutting guide is 3D-printed to fit your bone one way only. In theatre the guide transfers the plan faithfully — cut, wedge, plate and screw positions are all decided before the first incision.
Why I use PSI:
- Multiplanar correction — coronal alignment, tibial slope and rotation corrected together in a single cut, rather than trading one for another
- Multiple injuries in one sitting — osteotomy, ACL reconstruction and meniscal root repair planned as one construct, with tunnels and screws de-conflicted in software before surgery
- Published accuracy — the system I use has published a mean error of 0.2 degrees between planned and achieved alignment
- Safety in complex deformity — double-level and revision cases are rehearsed on screen before theatre
I presented three of my own PSI-planned cases at the Northern Osteotomy Masterclass 2026 — two of them are shown below.
Recent cases
Bilateral knock knees after failed guided growth — double-level osteotomies
A young patient with painful knock-kneed (valgus) alignment of both legs. Guided growth surgery in adolescence had not corrected the deformity, which sat in both the femur and the tibia. Each leg was corrected with a double-level osteotomy, restoring both legs to neutral alignment.
One knee, four problems — solved in one operation
A 35-year-old self-employed roofer with medial compartment arthritis, a medial meniscus tear, a lateral meniscus root tear and an ACL rupture — 7.8° of varus on weight-bearing films and a tibial slope of 16.9°. He wanted one operation, not four. Using PSI, a multiplanar medial opening-wedge HTO corrected the varus and reduced the slope to 9.9° in the same cut, combined with ACL reconstruction and lateral meniscus root repair in a single sitting. The guides positioned the tunnels; every screw was planned to stay clear of them.
Failed ACL graft with a 17.4° tibial slope — slope-reducing osteotomy
A re-ruptured ACL graft with one clear reason behind it: a tibial slope of 17.4°. A slope-reducing anterior closing-wedge osteotomy brought the slope down to 6°, combined with single-stage revision ACL reconstruction and lateral extra-articular tenodesis (LET). Correcting the slope protects the new graft from the forces that destroyed the old one.
Varus arthritis with ACL instability — combined HTO + ACL reconstruction
Medial compartment arthritis in a varus, ACL-deficient knee. Realignment alone would leave the knee unstable; reconstruction alone would fail in the malaligned knee. A medial opening-wedge HTO and ACL reconstruction were performed together.
Varus overload — medial opening-wedge HTO
A varus knee overloading the medial compartment, corrected with a planned medial opening-wedge high tibial osteotomy. The weight-bearing line now passes through the healthy part of the joint.
Severe varus — correction at both femoral and tibial level
When deformity is too large for a single cut, correcting both bones keeps the joint line level. Planned on calibrated long-leg films and corrected with femoral and tibial osteotomies in one operation.
All images are shared with patient consent and have been de-identified.
A national service for complex knee realignment
Osteotomy is a subspecialist operation, and complex corrections — double-level, slope-reducing, derotational and combined ligament cases — are concentrated in a small number of hands nationally. Mr Riaz receives referrals from consultant colleagues and physiotherapists across the UK and welcomes second opinions on failed ACL grafts, malalignment and joint preservation. Patients are seen at Spire Elland Hospital (01422 702951) and The Huddersfield Hospital, Circle Health Group (01484 533131), both minutes from the M62 with easy access from Manchester, Leeds and beyond. Self-pay and all major insurers accepted.
Related reading: revision ACL surgery • ACL reconstruction • cartilage repair & AutoCart • robotic knee replacement • why tibial slope matters in revision ACL.
Common questions
How long is recovery after a knee osteotomy?
Most patients are on crutches with protected weight-bearing for the first weeks, back to desk-based work within two to four weeks, and progressing to full weight-bearing as the bone unites — typically assessed on X-ray at six and twelve weeks. Return to impact sport and heavy manual work is usually from four to six months, guided by healing and rehabilitation.
Osteotomy or knee replacement — which is right for me?
They answer different questions. A replacement swaps the joint; an osteotomy preserves your own knee by correcting the mechanics that are wearing it out. For younger, active patients with arthritis limited to one compartment, osteotomy keeps running, pivoting sport and manual work realistic in a way replacement rarely does — and it does not burn bridges: a knee replacement remains possible later if ever needed.
Why does my ACL graft keep failing?
When a well-performed reconstruction fails without major new injury, the cause is often the shape of the bone: varus alignment or a high posterior tibial slope silently overloading the graft. That is why every revision ACL patient in this practice has full-length alignment films and slope measurement — and why correcting the bone with an osteotomy is sometimes the single most important part of the revision.
