Effect of J-Shaped Incision After Total Knee Arthroplasty (J-TKA)

J-Shaped Incision Reduces Peri-incisional Numbness and Pain After Primary Total Knee Arthroplasty: A Prospective Randomized Controlled Trial

This prospective randomized controlled trial evaluates whether a modified J-shaped skin incision can reduce peri-incisional numbness after primary total knee arthroplasty (TKA) compared with the conventional midline skin incision. Peri-incisional numbness is a common postoperative complaint after TKA and is thought to be mainly related to injury of the infrapatellar branch of the saphenous nerve. Although often considered a minor issue, it may adversely affect postoperative comfort, pain perception, and patient satisfaction.

A total of 62 patients undergoing primary TKA for Kellgren-Lawrence grade 4 varus knee osteoarthritis were randomized to either a conventional midline incision or a modified J-shaped incision. In the J-shaped technique, the distal part of the incision is curved laterally at the level of the tibial tuberosity in an effort to decrease injury to the infrapatellar branch of the saphenous nerve. The primary outcome is the extent of peri-incisional sensory loss, assessed using Semmes-Weinstein 10-g monofilament testing with a grid-mapping method before surgery and at 2 and 6 months after surgery. Secondary outcomes include pain scores, functional knee scores, range of motion, blood loss, tourniquet time, and wound-related complications.

Study Overview

• Status: Completed
• Conditions: Osteoarthritis, Knee
• Intervention / Treatment: Procedure: Conventional Midline Incision; Procedure: J-shaped Incision

Detailed Description

Total knee arthroplasty is an effective surgical treatment for advanced knee osteoarthritis; however, peri-incisional numbness is a frequent postoperative finding. This sensory disturbance is commonly attributed to injury of the infrapatellar branch of the saphenous nerve during the standard anterior skin incision. Although peri-incisional numbness is often not regarded as a major complication, it may negatively influence postoperative comfort and patient satisfaction and may also be associated with persistent local pain.

This study was designed to investigate whether a modified J-shaped skin incision could reduce peri-incisional numbness compared with the conventional midline incision in patients undergoing primary TKA. The underlying rationale is that altering the distal course of the skin incision laterally near the tibial tuberosity may help decrease injury to the infrapatellar branch of the saphenous nerve while preserving standard surgical exposure and not increasing operative difficulty or wound-related complications.

In this prospective randomized controlled trial, 62 patients with Kellgren-Lawrence grade 4 varus osteoarthritis scheduled for primary TKA were allocated to one of two groups: a conventional midline incision group or a modified J-shaped incision group. In the modified technique, the distal portion of the incision is curved laterally by approximately 3 cm at the level of the tibial tuberosity. All participants undergo peri-incisional sensory evaluation preoperatively and again at 2 and 6 months postoperatively. Sensory loss is quantified using Semmes-Weinstein 10-g monofilament testing combined with a grid-mapping method to determine the area of numbness.

The primary outcome measure is the area of peri-incisional numbness after surgery. Secondary outcome measures include postoperative pain assessed by visual analog scale (VAS), functional outcomes assessed by The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS), Hospital for Special Surgery Knee-Rating Scale (HSS) and Anterior Knee Pain Scale (AKPS) scores, range of motion, estimated blood loss, tourniquet time, and wound-related complications. These measures are intended to determine whether the modified incision provides sensory and pain-related benefits without adversely affecting clinical recovery, surgical efficiency, or wound healing.

Based on the study findings summarized in the abstract, the modified J-shaped incision was associated with a significantly smaller area of postoperative numbness at both 2 and 6 months and with lower pain scores at 6 months, while functional scores, range of motion, blood loss, tourniquet time, and wound-related complications were similar between groups. These findings support the hypothesis that a simple modification of the skin incision may improve postoperative sensory outcomes and comfort after primary TKA without increasing surgical risk.

• Study Type: Interventional
• Enrollment (Actual): 62
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Istanbul
    • Ataşehir, Istanbul, Turkey (Türkiye), 34752
      • Fatih Sultan Mehmet Training and Research Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Adults undergoing primary total knee arthroplasty
• Diagnosis of Kellgren-Lawrence grade 4 varus knee osteoarthritis
• Planned treatment with primary total knee arthroplasty
• Ability to provide written informed consent
• Ability to comply with postoperative follow-up evaluations

Exclusion Criteria:

• Valgus knee deformity
• Revision total knee arthroplasty
• Previous surgery on the affected knee
• History of periarticular fracture around the knee
• Pre-existing sensory deficit or neurologic disorder affecting the operative lower extremity
• History of lumbar disc herniation
• Known neuromuscular disease
• Peripheral vascular disease
• Inability to comply with follow-up and postoperative evaluations
• Refusal or inability to provide informed consent

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Midline Incision; Participants undergo primary total knee arthroplasty using a conventional midline skin incision.	Procedure: Conventional Midline Incision; A conventional midline skin incision is used during primary total knee arthroplasty.; Other Names: Standard midline incision
Experimental: J-shaped Incision; Participants undergo primary total knee arthroplasty using a modified J-shaped skin incision, in which the distal portion of the incision is curved laterally at the level of the tibial tuberosity.	Procedure: J-shaped Incision; A modified J-shaped skin incision is used during primary total knee arthroplasty, in which the distal portion of the incision is curved laterally at the level of the tibial tuberosity.; Other Names: Modified J-shaped incision

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Area of peri-incisional sensory loss	The extent of peri-incisional sensory loss will be assessed using Semmes-Weinstein 10-g monofilament testing combined with a standardized grid-mapping method to quantify the area of numbness around the surgical incision.	2 months and 6 months postoperatively

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Postoperative pain	Postoperative pain will be assessed using the Visual Analog Scale (VAS) for pain at 2 months and 6 months postoperatively. The VAS ranges from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain. Higher scores indicate worse pain.	2 months and 6 months postoperatively
Range of motion	Knee range of motion will be measured clinically in degrees.	2 months and 6 months postoperatively
Intraoperative Blood Loss	Intraoperative blood loss will be recorded during the surgical procedure. Blood loss will be measured in milliliters (mL). Higher values indicate greater blood loss.	Intraoperative period
Tourniquet Time	Tourniquet time will be recorded during the surgical procedure. Tourniquet time will be measured in minutes. Higher values indicate longer tourniquet use.	Intraoperative period
Incision Length	Incision length will be measured intraoperatively in centimeters (cm). Higher values indicate a longer skin incision.	Intraoperative period
Wound complications	Postoperative wound-related complications will be assessed clinically.	Up to 6 months postoperatively
Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Score	Functional outcome will be assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at 2 months and 6 months postoperatively. If reported on a 0 to 100 scale, 0 indicates the worst symptoms/function and 100 indicates the best symptoms/function. Higher scores indicate better outcome.	2 months and 6 months postoperatively
Knee injury and Osteoarthritis Outcome Score (KOOS)	Functional outcome will be assessed using the Knee injury and Osteoarthritis Outcome Score (KOOS) at 2 months and 6 months postoperatively. KOOS subscale scores range from 0 to 100, where 0 indicates extreme knee problems and 100 indicates no knee problems. Higher scores indicate better outcome.	2 months and 6 months postoperatively
Hospital for Special Surgery (HSS) Knee Score	Functional outcome will be assessed using the Hospital for Special Surgery Knee Score (HSS) at 2 months and 6 months postoperatively. The HSS score ranges from 0 to 100, with higher scores indicating better knee function.	2 months and 6 months postoperatively
Kujala Anterior Knee Pain Scale Score	Functional outcome will be assessed using the Kujala Anterior Knee Pain Scale at 2 months and 6 months postoperatively. The score ranges from 0 to 100, with higher scores indicating better knee function and fewer symptoms.	2 months and 6 months postoperatively

Collaborators and Investigators

• Sponsor: Fatih Sultan Mehmet Training and Research Hospital

Publications and helpful links

General Publications

• James NF, Kumar AR, Wilke BK, Shi GG. Incidence of Encountering the Infrapatellar Nerve Branch of the Saphenous Nerve During a Midline Approach for Total Knee Arthroplasty. J Am Acad Orthop Surg Glob Res Rev. 2019 Dec 12;3(12):e19.00160. doi: 10.5435/JAAOSGlobal-D-19-00160. eCollection 2019 Dec.
• MacDonald B, Kurdin A, Somerville L, Ross D, MacDonald S, Lanting B. The Effect of Sensory Deficit After Total Knee Arthroplasty on Patient Satisfaction and Kneeling Ability. Arthroplast Today. 2021 Jan 11;7:264-267.e2. doi: 10.1016/j.artd.2020.11.020. eCollection 2021 Feb.

Study record dates

Study Major Dates

• Study Start (Actual): September 17, 2025
• Primary Completion (Actual): April 17, 2026
• Study Completion (Actual): May 17, 2026

Study Registration Dates

• First Submitted: March 27, 2026
• First Submitted That Met QC Criteria: April 1, 2026
• First Posted (Actual): April 7, 2026

Study Record Updates

• Last Update Posted (Actual): May 29, 2026
• Last Update Submitted That Met QC Criteria: May 28, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Total Knee Arthroplasty; Knee Osteoarthritis; Numbness; Saphenous Nerve; J-shaped Incision
• Additional Relevant MeSH Terms: Neurologic Manifestations; Musculoskeletal Diseases; Nervous System Diseases; Arthritis; Joint Diseases; Rheumatic Diseases; Osteoarthritis; Sensation Disorders; Somatosensory Disorders; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Osteoarthritis, Knee; Hypesthesia
• Other Study ID Numbers: J-TKA-2026

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No