Leg Length Discrepancy After Hip Replacement

Leg length discrepancy refers to a difference in the length of the legs following total hip replacement surgery. This condition can occur when one leg feels longer or shorter than the other, either because of an actual difference in bone length or a functional imbalance where the length is perceived differently. Although it can be concerning for patients, this complication is rare and often resolves naturally within a few months after surgery.

X-ray of the pelvis showing leg length measurement in a post-op total hip replacement of the right hip.

How Common It Is and Who Gets It? (Epidemiology)

Leg length discrepancy after hip replacement is uncommon, thanks to modern surgical techniques and implant designs. When it does occur, it is usually mild and temporary. The condition tends to affect patients recovering from hip arthritis who have pre-existing pelvic tilt or tight muscles around the hip joint. Both men and women can experience this issue, but it is more likely in patients with advanced deformity or prior surgery on the same hip.

Why It Happens – Causes (Etiology and Pathophysiology)

Leg length discrepancy may occur due to several factors during or after surgery:

• Pelvic tilt and muscle tightness: Arthritis causes shortening of the diseased hip, and the body compensates with pelvic tilting. After surgery, the new joint restores normal length, but the tight muscles around the hip may cause the pelvis to remain tilted, making the leg feel longer.
• Surgical technique: Surgeons aim for joint stability and proper alignment. Sometimes, to prevent dislocation, a slightly longer implant or neck may be used, leading to minimal leg lengthening.
• Implant positioning: Malposition of the prosthetic cup or the use of smaller implants in unplanned surgeries can create true shortening.
• Soft tissue balance: Overly tight or lax soft tissues can change leg mechanics and create the perception of uneven length.

How the Body Part Normally Works? (Relevant Anatomy)

The hip joint is a ball-and-socket joint connecting the femoral head (thigh bone) to the acetabulum (hip socket). In a total hip replacement, these structures are replaced with metal and plastic implants designed to restore normal alignment and movement. The surrounding muscles and ligaments provide stability and control. When these soft tissues tighten or relax unevenly, it can alter pelvic balance, leading to the sensation of one leg being longer or shorter.

What You Might Feel – Symptoms (Clinical Presentation)

Patients may notice that one leg feels longer or shorter when standing or walking. They might limp or experience pain in the hip, thigh, or lower back. In true leg lengthening, stretched nerves such as the sciatic or femoral nerve can cause numbness, tingling, or weakness. In true shortening, muscle tension around the hip may be reduced, leading to instability or difficulty balancing. Discomfort typically improves as the body adjusts after surgery.

How Doctors Find the Problem? (Diagnosis and Imaging)

Doctors diagnose leg length discrepancy through a combination of patient history, physical examination, and imaging. The examination includes visual inspection of posture, pelvic alignment, and gait. X-rays are commonly used to measure leg length precisely and determine if the discrepancy is true or functional. CT scans may be ordered in rare cases for more detailed assessment of implant positioning.

Classification

Leg length discrepancy can be classified as:

• True discrepancy: A measurable difference in bone length due to implant positioning or surgical adjustments.
• Functional discrepancy: The legs are equal in length, but muscle tightness or pelvic tilt creates the sensation of unevenness.
  Most postoperative discrepancies are functional and improve within a few months.

Other Problems That Can Feel Similar (Differential Diagnosis)

Other conditions that can mimic leg length discrepancy include pelvic obliquity, scoliosis, muscle imbalance, hip or knee contractures, and back problems. Careful examination helps rule out these causes.

Intraoperative image showing loading of the prosthetic acetabular shell.

Treatment Options

Non-Surgical Care – Most cases improve naturally. Physical therapy and stretching exercises help relax tight muscles and correct pelvic tilt. The body often adapts to minor differences (less than 10 mm) without intervention. In some cases, a shoe lift or insert may be recommended for comfort and balance after 6 months.
Surgical Care – Revision hip replacement is rarely required and reserved for severe, persistent discrepancies. Surgery may involve adjusting implant size or position to restore equal leg length.

Recovery and What to Expect After Treatment

Most patients experience gradual improvement in leg length sensation and gait within three to six months. Physical therapy is essential for retraining posture, improving flexibility, and restoring balance. For patients using a shoe lift, comfort typically improves within weeks. True surgical revisions require longer recovery but are uncommon.

Possible Risks or Side Effects (Complications)

Potential complications include persistent pelvic tilt, nerve stretching from lengthening, hip instability from shortening, or continued limp. Lower back pain may develop from altered alignment. However, these risks are rare with proper rehabilitation and monitoring.

Long-Term Outlook (Prognosis)

The outlook for patients with leg length discrepancy after hip replacement is excellent. Most cases resolve without surgery, and long-term function and satisfaction remain high. The advanced precision of modern implants and surgical planning has made significant discrepancies exceedingly rare.

Out-of-Pocket Costs

Medicare

CPT Code 27134 – Revision of Both Components to Correct Leg Length Discrepancy (Revision Total Hip Arthroplasty, Both Components): $448.00

CPT Code 27137 – Revision of Acetabular Component Only (Revision Total Hip, Acetabular Side): $345.69

CPT Code 27138 – Revision of Femoral Component Only (Revision Total Hip, Femoral Side): $359.01

CPT Code 27556 – Limb Lengthening Procedure (Femoral Lengthening, Single Stage): $207.33

CPT Code 27557 – Limb Lengthening Procedure (Femoral Lengthening, Staged): $246.64

Medicare Part B typically covers 80% of the approved cost for these procedures after your annual deductible has been met, leaving you responsible for the remaining 20%. Supplemental Insurance plans such as Medigap, AARP, or Blue Cross Blue Shield generally cover that remaining 20%, minimizing or eliminating out-of-pocket expenses for Medicare-approved surgeries. These plans coordinate with Medicare to fill the coverage gap and significantly reduce patient costs.

If you have Secondary Insurance, such as TRICARE, an Employer-Based Plan, or Veterans Health Administration coverage, it acts as a secondary payer. These plans often cover any remaining coinsurance or small deductibles, which typically range between $100 and $300, depending on your plan and provider network.

Workers’ Compensation

If your hip revision or limb lengthening procedure is required due to a work-related injury or complication from a prior work-related surgery, Workers’ Compensation will cover all associated medical expenses, including surgery, rehabilitation, and postoperative care. You will not have any out-of-pocket expenses, as the employer’s insurance carrier directly pays for all approved treatments.

No-Fault Insurance

If your hip or leg surgery is related to an automobile accident, No-Fault Insurance will typically cover the full cost of your treatment, including revision arthroplasty, limb lengthening, and rehabilitation. The only potential out-of-pocket cost may be a small deductible or co-payment depending on your insurance policy.

Example

Robert Lewis experienced leg length discrepancy following a previous hip replacement and required a revision of both components (CPT 27134) with an estimated Medicare out-of-pocket cost of $448.00. Later, he underwent a limb lengthening procedure (CPT 27557) costing $246.64 out of pocket under Medicare. Because Robert had supplemental insurance through Blue Cross Blue Shield, his remaining balances were fully covered, leaving him with no out-of-pocket expenses for either surgery.

Frequently Asked Questions (FAQ)

Q. Is leg length discrepancy after hip replacement permanent?
A. Usually not. Most cases resolve within six months through physical therapy and natural body adaptation.

Q. When should I worry about leg length differences?
A. If the sensation persists beyond six months or causes ongoing pain or limping, consult your orthopedic surgeon.

Q. Can leg length differences be corrected without surgery?
A. Yes. Stretching, physical therapy, and shoe lifts effectively correct most mild discrepancies.

Summary and Takeaway

Leg length discrepancy after total hip replacement is a rare and usually temporary issue. It may result from muscle tightness, pelvic tilt, or surgical adjustments made for stability. Most patients improve with stretching, physical therapy, and time. In very few cases, surgical revision may be considered. With proper care and rehabilitation, patients typically regain balance and comfort within a few months.

Clinical Insight & Recent Findings

After undergoing total hip replacement, some patients may notice a leg length discrepancy (LLD), which can result from several factors such as the surgical technique, preoperative joint deformities, or muscle tightness around the pelvis. A recent study has examined various techniques for reducing LLD after THA, specifically comparing the use of a positioning table with intra-operative radiography, a standard table with radiography, and a standard table without radiography.

Despite the differences in approaches, the study found no significant advantages in controlling LLD with either method. The most important factor was the surgeon’s skill and experience, suggesting that LLD management remains a complex challenge that requires individualized care. (“Study on factors affecting leg length discrepancy after hip replacement – see PubMed.“)

Who Performs This Treatment? (Specialists and Team Involved)

Leg length discrepancy is managed by orthopedic surgeons specializing in hip replacement. The care team may include physical therapists for rehabilitation, radiologists for imaging evaluation, and orthopedic nurses who assist with patient recovery and follow-up.

When to See a Specialist?

If you notice a limp, uneven walking pattern, or persistent pain after hip replacement, you should schedule a follow-up with your orthopedic surgeon. Early evaluation ensures appropriate treatment and faster recovery.

When to Go to the Emergency Room?

Seek emergency care if you experience severe pain, sudden inability to walk, signs of nerve injury such as numbness or weakness, or evidence of hip dislocation following surgery.

What Recovery Really Looks Like?

Recovery typically involves physical therapy, mild soreness during stretching, and gradual improvement in leg balance. Some patients use shoe inserts temporarily. Most resume normal activities comfortably within three to six months.

What Happens If You Ignore It?

Ignoring leg length discrepancy can lead to persistent limping, back pain, or uneven wear on the spine and joints. It may also affect the longevity and stability of the hip implant.

How to Prevent It?

Prevention starts with careful preoperative templating—measuring implant size and placement before surgery. Modern technology such as robotic-assisted surgery and intraoperative imaging further enhances accuracy, minimizing the risk of leg length differences.

Nutrition and Bone or Joint Health

A diet rich in calcium, vitamin D, and protein supports bone healing and joint health after surgery. Maintaining hydration and avoiding smoking or excessive alcohol use promotes better recovery.

Activity and Lifestyle Modifications

Gentle stretching and strengthening exercises help maintain pelvic alignment and prevent stiffness. Patients should gradually resume walking and low-impact activities like swimming or cycling. Good posture and adherence to physical therapy are key for lasting results.