International Orthopaedics - 2026-06-26 - Journal Article
The effect of J-shaped incision versus standard midline incision on numbness and pain in primary total knee arthroplasty: a prospective randomized controlled trial.
Kahraman HÇ, Kılınç BE, Yavuz O, Erdem HF, Yılmaz B
Topics
Key Takeaway
A J-shaped incision (distal limb lateralized 3 cm at the tibial tuberosity) reduced anterior knee numbness area by 54% at 2 months (3.5 vs. 7.6 cm²) and 60% at 6 months (2.1 vs. 5.3 cm²) compared to standard midline incision in primary TKA.
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Summary
This RCT asked whether lateralizing the distal limb of the standard midline TKA incision by 3 cm (J-shaped) reduces peri-incisional numbness versus standard midline incision in KL grade 4 OA patients. Numbness area was mapped with 10-g Semmes-Weinstein monofilaments at 2 and 6 months. The J-shaped group had significantly smaller sensory deficit areas at both timepoints (p<0.01) and lower VAS pain at 6 months (p=0.048), with equivalent functional scores and complication rates.
Key Limitation
The 6-month follow-up is insufficient to determine whether numbness differences persist or resolve with natural nerve regeneration, which is the critical question for justifying routine adoption of the longer J-shaped incision.
Original Abstract
INTRODUCTION
Peri-incisional numbness is a common but often underestimated complaint after primary total knee arthroplasty (TKA) and may negatively affect early postoperative patient satisfaction. This randomized controlled trial aimed to determine whether a modified J-shaped skin incision, created by lateralizing the distal limb of the standard midline incision by 3 cm at the tibial tuberosity, reduces peri-incisional numbness and pain after primary TKA.
MATERIALS AND METHODS
Sixty-two patients undergoing primary TKA for Kellgren-Lawrence grade 4 osteoarthritis were randomized to either a standard midline incision or a modified J-shaped incision. All procedures were performed using a medial parapatellar arthrotomy and standardized perioperative protocols. The primary outcome was the area of postoperative anterior knee numbness, assessed using grid-based 10-g Semmes-Weinstein monofilament mapping at two and six months. Secondary outcomes included VAS pain, WOMAC, KOOS, HSS, Kujala score, range of motion, and perioperative parameters.
RESULTS
Baseline demographic and perioperative characteristics were comparable between groups, except for longer incision length in the J-shaped group. The standard incision group had a significantly larger sensory deficit area than the J-shaped group at both two months and six months postoperatively (7.6 ± 4.2 vs. 3.5 ± 2.9 cm. 2 and 5.3 ± 3.2 vs. 2.1 ± 2.4 cm. 2 , respectively; both p < 0.01). Postoperative VAS pain was significantly lower in the J-shaped group at six months (p = 0.048). Functional outcomes improved significantly in both groups, with no significant between-group differences.
CONCLUSIONS
The modified J-shaped skin incision significantly reduced peri-incisional numbness and early postoperative pain after primary TKA without increasing complications. This simple incision modification may improve early sensory recovery while preserving standard medial surgical exposure.
TRIAL REGISTRATION
ClinicalTrials.gov, NCT07514598, ( https://clinicaltrials.gov/study/NCT07514598 ).