Alteration in skin sensation following knee arthroplasty and its impact on kneeling ability: a comparison of three common surgical incisions.

PURPOSE: Disturbance in skin sensation is a recognised, often unpleasant consequence of knee replacement for many patients and may affect function especially kneeling. The aim of this study was to compare post-operative changes in skin sensation following total (TKA) and unicompartmental knee (UKA) arthroplasties using three different incision types and its effect on kneeling ability.

METHODS: Skin sensation was recorded using a purpose-designed grid over the front of the knee in 72 patients (78 knees) following knee arthroplasty. Surface area of sensory change, length of incision, and kneeling ability were recorded and compared between three different types of incision; long antero-medial and midline for TKA, and short medial for UKA.

RESULTS: The average length of the long antero-medial incision was 19 ± 5 cm with an average area of sensory alteration of 88 ± 56 cm(2). The average length of the midline incision was 18 ± 3 cm with an average area of sensory alteration of 57 ± 52 cm(2). The short medial incision used for UKA averaged 11 ± 3 cm in length with an average area of sensory alteration of 54 ± 45 cm(2). Long antero-medial produced a significantly greater area of sensory alteration than standard short medial (P = 0.017), but not the midline incision. There was a significant positive correlation of incision length with reduced sensation. Patients unable to kneel demonstrated a significantly larger area of hypersensitivity than patients who could kneel (P = 0.002).

CONCLUSIONS: Increased length of incision results in a greater surface area of sensory change in the front of the knee. This finding was greatest in the long antero-medial incisions used in TKA. The inability to kneel following knee arthroplasty is associated with increased area of hypersensitivity of the anterior knee.

LEVEL OF EVIDENCE: Prospective comparative study, Level II.