Patient Lynne Wallis was left with her right leg 14 millimetres shorter than her left following knee replacement operations at her local hospital in the UK, highlighting widespread risks of post-operative leg length discrepancy.
Leg length discrepancy of more than 10 millimetres affects a significant proportion of the estimated 200,000 patients undergoing knee and hip replacement surgery in the UK each year, frequently leading to chronic lower back pain, sciatic nerve pain, and an altered gait.
Leaving her local hospital last month, Wallis reported she was finally able to stride out normally after enduring four years of severe lower back and sciatic pain that dogged her following joint surgery.
The pain was caused by an unrecognised leg length difference resulting from her knee replacement operations, which was further aggravated because she was wearing an orthotic shoe insert in the wrong shoe.
Diagnosis of leg length discrepancy
Wallis had originally been diagnosed with leg length discrepancy approximately 15 years ago due to scoliosis, a curvature of the spine that causes the pelvis to lift on one side and makes one leg appear shorter despite equal bone lengths. The spinal condition caused lower back pain on her left side from the age of 40 and contributed to severe osteoarthritis in both knees, alongside a serious skiing accident 16 years ago.
To manage the scoliosis, an orthotist provided her with a one-centimetre heel lift insert for her left shoe 15 years ago, which successfully reduced shooting pain in her left leg. However, after undergoing a left knee replacement in May 2021, Wallis developed acute sciatic pain in her lower back and left buttock, which she mistakenly attributed to worsening scoliosis while continuing to wear the left shoe insert.
Following a second knee replacement on her right leg in October 2022, her pain persisted. By July this year, after the discomfort became unbearable, a consultation with a different NHS orthotist revealed that her right leg had been left 14 millimetres shorter than her left as a result of the two surgical procedures.
The specialist discovered that Wallis had been propping up what was now her longer left leg with her original orthotic insert, worsening her condition. After being fitted with a 14-millimetre orthotic insert for her right shoe, Wallis recalled exclaiming in a dramatic whisper, "oh my God," as her awkward, side-to-side rocking gait vanished and her back pain cleared within weeks.
Surgical causes and communication risks
Alex Chipperfield, an orthopaedic surgeon at the private Benenden Hospital in Kent, explained that a leg length discrepancy exceeding 10 millimetres frequently causes physical difficulties such as a changed gait or persistent pain. He noted that while most people are born with natural leg length variations of up to 5 millimetres, surgical discrepancies occur due to the sizing of joint implants and the depth to which they are inserted into the bone.
According to Chipperfield, implants "can be put in too high or too low" during surgery. In hip replacements, if the cup component sits higher or lower on the pelvis, or if the stem sits deeper or proud in the thigh bone, the physical length of the leg changes. Additionally, patients with arthritis in the untreated leg or spine may experience functional differences when one joint is restored to proper anatomy while the untreated side remains shortened by cartilage and bone loss.
Chipperfield emphasised that all surgeons should warn patients about the risks of leg length changes prior to surgery, noting that medical litigation often stems from poor communication between surgeons and patients when potential complications are not made clear. Although potential risks may be listed in pre-operative information leaflets, Wallis noted that no healthcare provider had explicitly explained the risk prior to her operations in 2021 and 2022.
Post-operative screening and physiotherapy
Liam Stapleton, a sports physiotherapist and orthotics specialist working in London private practice and at NHS hospitals in Kent, highlighted lower back pain and a rolling gait as primary signs of leg length discrepancy. He called for mandatory post-operative screening and greater awareness within the medical profession to catch discrepancies early.
Stapleton stated that physiotherapists are best positioned to perform screening during routine post-surgery rehabilitation, which every joint replacement patient undergoes. He added that operating surgeons should not conduct the screening themselves to avoid potential conflicts of interest regarding medical negligence claims.
To manage the condition, Stapleton encourages patients with leg length discrepancy to undertake structured rehabilitation programmes focused on improving core, hip, and leg strength, enabling the body to withstand minor length variations. In the most severe and disabling cases, patients may require revision surgery to refit or adjust the artificial joint.
Medical studies and legal compensation
Research indicates that leg length changes are common following joint replacement operations. A 2019 study published in The Bone & Joint Journal revealed that 80 per cent of knee replacement patients experience some degree of leg length discrepancy. Furthermore, a 2024 study in the journal Orthopaedics & Traumatology: Surgery & Research tracked 100 knee replacement patients and found that around 25 per cent had a discrepancy of at least 10 millimetres, with researchers suggesting the issue "perhaps explains some patient dissatisfaction."
A recent medical review indicated that 10 to 14 per cent of hip and knee replacement patients report dissatisfaction with their outcomes, citing ongoing pain and reduced function. Historical data published in The Journal of Bone and Joint Surgery in the 1970s showed that up to 27 per cent of hip replacement patients required heel lifts for 10-millimetre discrepancies, while a 1997 study in HIP International found nearly 10 per cent of hip replacement patients were left with discrepancies over 10 millimetres.
The clinical consequences of uncorrected leg length discrepancy were highlighted last month when the NHS paid £85,000 in compensation to a woman whose leg was left 33 millimetres longer following hip replacement surgery. Solicitors acting for the patient stated the discrepancy was caused by poor surgical planning and an undersized implant, while an assessing surgeon warned she would likely require spinal surgery if the limb length was not corrected.
Non-surgical causes and patient advice
Leg length discrepancy can also develop without surgery due to congenital differences in the length of the femur or tibia bones, or following bone fractures. Functional or apparent leg length discrepancy can occur when bone lengths are equal but muscle tightness, flat feet, joint stiffness, weak gluteal or abdominal muscles, or a pelvic tilt caused by prolonged sitting make one leg function as shorter.
Reflecting on her experience, Wallis expressed regret that she lost four years of pain-free living because she was unaware that knee replacements could alter leg length. She urged all patients preparing for hip or knee surgery to demand immediate post-operative screening for leg length discrepancy. Meanwhile, public figures have also raised awareness of related spinal conditions, with actress Rita Simons sharing insight into her scoliosis while celebrating her "wonderful wonky body."
