ORIGINAL ARTICLE • KNEE - ARTHROPLASTY A comparison of kneeling ability after lateral or midline incisions in total knee arthroplasty Nicholas Calvert 1 • Lachlan Milne 1 • Markus Kuster 1,2 Received: 9 May 2016 / Accepted: 27 July 2016 Ó Springer-Verlag France 2016 Abstract Kneeling is often impaired following total knee replacement. There is no clinical study comparing a lateral to a midline skin incision with regard to kneeling. Patients with a well-functioning total knee replacement enrolled in the trial. The participants with a lateral skin incision were matched with those with a standard midline incision. Twenty-two patients were enrolled in the study: 10 had a lateral skin incision, and 12 had a midline incision. Those with a lateral skin incision had a significantly higher For- gotten Joint Score than with a midline skin incision (Dif- ference of Means Lateral vs Midline = 10.9 [p value 0.0098]), and an improved ability to kneel at 110 degrees of flexion (Kneeling Ability Test; Difference of Means Lateral vs Midline = 41.7 [p value 0.020]). These results suggest that a lateral skin incision may provide reduced joint awareness and improved kneeling ability. Further investigation with a randomised controlled trial is needed. Keywords Total knee arthroplasty Á Kneeling Á Incision Introduction Kneeling is an important function of the knee joint. It is necessary for certain occupations such as plumbing or carpet laying and recreational activities such as gardening. In many religions and cultures it plays a pivotal role in praying and sitting practices. Hassaballa et al. [1] found that 37 % of their patients had either moderate difficulty or a complete inability to kneel 2 years after total knee arthroplasty. Dawson et al. [2] found that 51 % of their patients undergoing total knee arthroplasty found it nearly impossible to kneel. Scar position and skin hypoesthesia have been implicated in decreasing kneeling ability after total knee arthroplasty [3–6]. Despite this there has been a lack of research into improving kneeling ability in arthro- plasty patients with initial incision placement or research into methods of assessing kneeling ability. The purpose of this preliminary comparative study is to compare the kneeling ability of patients with a midline skin incision to those with a laterally placed skin incision using a novel kneeling ability scoring system. Methods Patients were enrolled through the hospital’s joint replacement assessment clinic. The study was approved by the Human Research Ethics Committee. Only patients with an excellent Knee Society Score greater than 85 in the knee domain at one year of follow-up were contacted to par- ticipate in the trial. The participants with a lateral skin incision, performed by a single surgeon, were compared with those with a standard midline incision, performed by two other surgeons. The lateral skin incision was placed 2 cm lateral to the midline. All patients underwent a medial parapatellar arthrotomy and an LCS Primary Total Knee Replacement (Depuy Orthopaedics Inc., Warsaw, Indiana) without patella resurfacing was implanted. Twenty-two patients were enrolled in the study, 10 with a lateral skin incision were matched to 12 with a midline incision & Nicholas Calvert Nicholas.calvert@health.wa.gov.au 1 Department of Orthopaedic Surgery, Royal Perth Hospital, Perth, WA 6000, Australia 2 University of Western Australia, Stirling Hwy, Crawley, WA 6069, Australia 123 Eur J Orthop Surg Traumatol DOI 10.1007/s00590-016-1831-6