Endurance sports after total knee replacement: a biomechanical investigation

Purpose: No biomechanical evaluation of total knee designs exists for loads occurring during sports activities. It was the purpose of the present stud y to evaluate the contact stress distribution and contact area of different knee joint designs for loads that occur during four common recreational en durance activities. Methods: Three different total knee designs were evalua ted for loads occurring during cycling (1.2 body weight (BW) at 80 degrees of knee flexion), power walking (4 BW at 20 degrees), hiking (8 BW at 40 de grees), and jogging (9 BW at 50 degrees) using Fuji pressure-sensitive film . The designs consisted of a flat tibial inlay, a curved inlay, and an inla y with mobile bearings. Five measurements were conducted for each load. The pressure sensitive films were scanned and analyzed using an image analysis program. Results: During cycling, the area with stress levels above the yi eld point of polyethylene (overloaded area) was below 15 mm(2) for each des ign. During power walking, the mobile bearing design showed no overloaded a rea, whereas it was below 50 mm(2) for the flat and curved design. During d ownhill walking and jogging, more than 140 mm(2) were overloaded for each d esign. Conclusions: It was concluded that patients after total knee replace ment should alternate activities such as power walking and cycling. For mou ntain hiking, patients are advised to avoid descents or at least use ski po les. Jogging or sports involving running should be discouraged after total knee replacement.