Early changes in muscle strength after total knee arthroplasty - A 6-monthfollow-up of 30 knees

We studied 30 patients with arthrosis in one knee operated on with a cement ed (n 26) or an uncemented total knee arthroplasty (TKA) (n 4). Full weight bearing from the first postoperative day was allowed in all patients, and t hey received standard postoperative physiotherapy. 1 week prior to surgery, and after 3 and 6 months, isokinetic and isometric muscle strength in both legs were measured, using a Cybex 6000 dynamometer. Isokinetic tests showe d a bilateral, significant, and progressive increase (30-53%) in flexor mus cle strength most pronounced in the operated legs. Isokinetic extensor stre ngth increased significantly (14-18%) in the operated legs, while in the co ntralateral legs, a limited increase was found. Isometric flexion strength significantly decreased in the operated knees (1 7%). Isometric extension strength showed a temporary decrease at 3 months, which returned to the preoperative level. No significant change in isometri c strength was observed in the contralateral legs. The knee pain during the muscle strength measurements decreased significantly from the preoperative level, which may indicate that the substantial pain relief within 3 months after a TKA is an important factor for evaluation of muscle strength.