A potential complication following hip or knee replacement surgery is leg length discrepancy (LLD), which can result in pain, altered gait, and patient dissatisfaction. While minor differences are common, discrepancies exceeding 10mm can lead to significant issues, according to orthopaedic surgeon Alex Chipperfield.
Studies indicate that a notable percentage of patients experience LLD after joint replacement. A 2019 study in The Bone & Joint Journal found that 80% of knee replacement patients have some degree of LLD. More recent research in Orthopaedics & Traumatology: Surgery & Research tracking 100 knee replacement patients revealed that approximately a quarter had a discrepancy of at least 10mm, which the authors suggested could explain some patient dissatisfaction.
These discrepancies can arise from several factors related to the surgery itself, including the size of the implant used and its placement within the bone. If an implant is positioned too high or too low, or if the cup in hip replacements sits higher or lower than the original joint, it can alter leg length. In cases where a patient has arthritis in the other leg or back, the operated leg may feel longer even if its bone length is unchanged, simply because the untreated joint is still shortened due to damage.
LLD is not solely a post-surgical issue. Some individuals are born with natural leg length differences, while others can develop it due to factors like broken bones, tight muscles, pelvic tilt, weak core muscles, flat feet, or joint stiffness. This is known as functional or apparent LLD, where bone lengths are equal but one leg seems shorter.
Signs of LLD can include lower back pain and a rolling gait. Sports physiotherapist Liam Stapleton emphasizes that patients should be screened for LLD post-surgery, suggesting that physiotherapists are well-positioned for this due to their involvement in post-operative care. He notes that discrepancies over 10mm often lead to problems like lower back pain. Stapleton also believes surgeons should avoid conducting these screenings themselves to prevent potential conflicts of interest regarding medical negligence claims.
Communication about the risks of LLD prior to surgery is crucial, according to Chipperfield. While potential risks might be listed in pre-operative information, the explicit discussion of these risks is often lacking. One individual's experience highlights this, detailing how knee replacements led to a significant leg length difference and subsequent pain, which was only resolved after a correct orthotic insert was prescribed. This individual had previously lived with LLD for years due to scoliosis, a spinal curvature, and inadvertently worsened the issue by using an orthotic in the wrong shoe after surgery.
In severe cases, revision surgery may be necessary to adjust or refit the joint. Experts like Stapleton also advocate for rehabilitation programs focusing on core, hip, and leg strength to help patients better manage LLD. The paramount concern remains ensuring patients are fully informed of the potential for LLD after joint replacement surgery and are screened appropriately to avoid prolonged pain and mobility issues.