• Quadriceps muscle force and activation, knee range of motion, and post-operative pain [ Time Frame: Measured pre-operatively; post-surgery at 48 hours; Months 1, 3, and 6; and Years 1 and 2 ] [ Designated as safety issue: No ]
  

• Functional performance (as determined by participants' self-reports, 6-minute walk distance, get up and go time, and functional stair climbing time) [ Time Frame: Measured pre-operatively; post-surgery at 48 hours; Months 1, 3, and 6; and Years 1 and 2 ] [ Designated as safety issue: No ]
  

More than 400,000 TKAs are performed each year in the United States to alleviate pain and disability associated with knee OA. Although this procedure reliably reduces pain and improves function in people with knee OA, recovery of the strength of the quadriceps muscle to normal levels is rare. For years after a TKA, performance while walking or while doing a more physically demanding activity, such as stair climbing, is also significantly lower in people who have had a TKA than in healthy adults of the same age. Within the past few years, less invasive TKA surgical techniques have been developed as promising alternatives to traditional TKA. Minimally invasive TKA, or TKA(min), achieves the same surgical objectives, but possibly without doing as much damage to the quadriceps muscle as is seen with traditional TKA. No studies, however, have specifically investigated how TKA(min) might preserve quadriceps muscle function. This study will determine whether TKA(min) is better than TKA at improving quadriceps muscle force production and activation, increasing knee range of motion, and reducing post-operative pain to improve overall functional outcomes.

Participants who are scheduled to undergo knee replacement surgery will be randomly assigned to receive either traditional TKA or TKA(min). Prior to surgery, participants will attend a 30-minute orientation session and undergo certain tests to evaluate knee function. Functional testing will include timed walking, stair climbing, balance testing, and knee flexibility measurements. Other evaluations will include thigh muscle strength and activation testing, which uses brief electrical pulses to determine if the muscles are contracted as much as possible, and health status questionnaires. After the operation, participants will be instructed to use walking aids, such as a walker, crutches, or a cane, for a period of time. Participants will attend study visits for repeat testing 48 hours following surgery; at Months 1, 3, and 6; and at Years 1 and 2.