Patient Lynne Wallis was left with a 14mm leg length discrepancy after knee replacement surgery at her local hospital in the UK, leading medical specialists to warn of widespread post-operative complications.
Wallis suffered four years of severe lower back and sciatic pain alongside an awkward, rocking gait after her operated right leg became significantly shorter than her left leg.
The condition, known as leg length discrepancy (LLD), affects up to 80 per cent of knee replacement patients to some degree, according to a 2019 study published in The Bone and Joint Journal.
Alex Chipperfield, an orthopaedic surgeon at the private Benenden Hospital in Kent, explained that a difference exceeding 10mm can trigger severe physical problems. "When it's more than 10mm it can cause problems such as a changed gait or pain," Mr Chipperfield said.
Research published in the journal HIP International in 1997 found nearly one in ten patients having a hip replacement were left with LLD in excess of 10mm.
Historical findings published in The Journal of Bone and Joint Surgery in the 1970s reported that as many as 27 per cent of patients having a hip replacement had LLD severe enough to require a heel lift, indicating a discrepancy of 10mm.
A 2024 study in the journal Orthopaedics and Traumatology: Surgery and Research tracked 100 people who had a knee replacement and found around a quarter had a discrepancy of at least 10mm.
The authors of the 2024 study added that the measurement difference "perhaps explains some patient dissatisfaction" with replacement joints. A recent review suggested that 10 to 14 per cent of hip and knee patients were dissatisfied, reporting issues including pain and function.
NHS payout and causes of leg length discrepancy
The warnings follow reports last month that the NHS had to pay out 85,000 pounds to a woman whose leg was left 33mm longer than the other following an operation to replace her arthritic hip.
Solicitors representing the patient stated the difference was due to the surgeon's poor planning for the operation and the use of an implant that was too small. An assessing surgeon later warned that if the leg length was not corrected, it was likely she would require surgery on her spine.
Around 200,000 patients undergo knee and hip replacements in the UK each year. While most people are born with minor differences in leg length of up to 5mm, Mr Chipperfield explained that surgical procedures can significantly alter limb measurements.
Post-operative LLD can stem from implant size and how deep components are positioned into the bone. "It can be put in too high or too low," Mr Chipperfield explained. In replacement hips, length changes occur if the cup sits higher or lower on the pelvis than the natural joint, or if the stem sits deeper or prouder in the thigh bone.
Non-surgical LLD can also occur from differences in the length of femurs (thigh bones) or tibias (shin bones), or as a result of broken bones. Functional or apparent LLD occurs when legs are equal in bone length but one seems shorter due to tight muscles, a tilted pelvis caused by prolonged sitting, weak gluteal or abdominal muscles, flat feet, or joint stiffness.
When a patient has arthritis in the other leg or back, restoring one hip can alter how both limbs feel. Mr Chipperfield noted that "when you restore one hip to its proper anatomy and the other side is still arthritic, the two legs can end up feeling different because the operated leg is genuinely a touch longer, often simply because the untreated hip is still sitting shortened because of the damage to the cartilage and bone."
He added: "The limbs feel longer even though they're not, the bone length is the same as before."
Post-operative screening and physical signs
Signs of LLD include lower back pain and a rolling gait, according to Liam Stapleton, a sports physiotherapist and orthotics specialist based in London private practice and at NHS hospitals in Kent.
Mr Stapleton called for mandatory screening of patients after surgery. "It should be something the physiotherapist includes as part of their screening for problems, everyone has physio after surgery, so they are best placed for this," he said.
He noted that "usually anything over 10mm can lead to difficulties such as lower back problems."
Mr Stapleton added that surgeons should not conduct the screening themselves. "The surgeon should not conduct the screening, because they would be keen to avoid pointing out something that may lead to a claim of medical negligence," he said.
Mr Chipperfield noted that litigation is often due to poor communication between the surgeon and the patient and the risks not being made clear prior to surgery.
Personal recovery and patient experience
For Wallis, LLD was initially diagnosed around 15 years ago due to scoliosis, a curvature in her spine that caused lower back pain on her left side since age 40. The spinal curvature caused her pelvis to lift on one side, making one leg seem shorter even though the bones were equal length.
Scoliosis also contributed to severe osteoarthritis in both her knees, which was further aggravated by a serious ski accident 16 years ago. Actress Rita Simons previously shared insight into her own scoliosis, celebrating her "wonderful wonky body."
Wallis was originally given a 1cm heel lift insole for her left shoe by an orthotist, which reduced shooting pain down her left leg. However, after undergoing left knee replacement surgery in May 2021 and right knee replacement surgery in October 2022, she developed acute sciatic pain in her lower back and left buttock.
Assuming her scoliosis was worsening, Wallis continued wearing the shoe lift in her left shoe. By July, with pain becoming unbearable, she consulted a different NHS orthotist specializing in orthotic shoe inserts.
Measurements revealed her right leg was now 14mm shorter than her left due to her two knee replacements. Wallis was unintentionally worsening her condition by propping up what had become her longer leg, prompting her to exclaim in a dramatic whisper: "oh my God."
The orthotist provided a 14mm insert for her right shoe, instantly eliminating her awkward rocking gait. Leaving her local hospital last month, Wallis walked normally for the first time in years, with her lower back and sciatic pain resolving after weeks.
To support recovery, Mr Stapleton encourages patients to undertake rehabilitation programs to improve core, hip, and leg strength. "This can all help to work through the impact of LLD, making the patient more robust so they can withstand a bit of difference in leg length," he explained.
In the most severe and disabling cases, patients with post-operative LLD may require revision surgery to get the joint surgically adjusted or refitted. Wallis urged all individuals undergoing knee or hip replacements to insist on immediate post-operative LLD screening.
