STUDY DESIGN: Prospective cohort study. OBJECTIVES: To measure changes in muscle strength, range of motion, and function from 2 weeks before to 6 months after total knee arthroplasty (TKA) and compare outcomes with data from a control group consisting of healthy adults. BACKGROUND: Total knee arthroplasty successfully alleviates pain from knee osteoarthritis, but deficits in function can persist long term. How impairments and functional limitations change over the first 6 months after TKA, compared to data from healthy adults, has not been well reported in the literature. METHODS: Twenty-four patients who underwent a primary unilateral TKA were compared to healthy adults (n = 17). All patients participated in a standardized rehabilitation program following surgery. Isometric quadriceps torque was assessed using an electromechanical dynamometer. Range of motion was measured actively and passively. Functional performance was assessed using the stair-climbing test, timed up-and-go test, 6-minute walk test, and single-limb stance time. Patients underwent testing at 2 weeks preoperatively and at 1, 3, and 6 months postoperatively. RESULTS: Compared to healthy older adults, patients performed significantly worse at all times for all measures (P<.05), except for single-limb stance time at 6 months (P>.05). One month postoperatively, patients experienced significant losses from preoperative levels in all outcomes. Patients recovered to preoperative levels by 6 months postoperatively on all measures, except knee flexion range of motion, but still exhibited the same extent of limitation they did prior to surgery. CONCLUSION: The persistent impairments and functional limitations 6 months after TKA with standard rehabilitation suggest that more intensive therapeutic approaches may be necessary to restore function of patients following TKA to the levels of healthy adults. LEVEL OF EVIDENCE: Therapy, level 2b.

J Orthop Sports Phys Ther 2010;40(9):559-567, Epub 6 August 2010. doi:10.2519/jospt.2010.3317

KEY WORDS: joint replacement, older adults, osteoarthritis, rehabilitation

STUDY DESIGN: Case report. BACKGROUND: Following total knee arthroplasty (TKA), restoration of normal quadriceps muscle function is rare. One month after surgery, quadriceps torque (force) is only 40% of preoperative values and quadriceps activation is only 82% of preoperative levels, despite initiating postoperative rehabilitation the day after surgery. Early application of neuromuscular electrical stimulation (NMES) offers a possible approach to minimize loss of quadriceps torque more effectively than traditional rehabilitation exercises alone. CASE DESCRIPTION: A 65-year-old female underwent a right, cemented TKA. Isometric quadriceps and hamstrings muscle torque were measured preoperatively and 3, 6, and 12 weeks after TKA. Quadriceps muscle activation was measured using a doublet interpolation technique at the same time points. The patient participated in a traditional TKA rehabilitation program augmented by NMES, which was initiated 48 hours after surgery and continued twice/day for the first 3 weeks, and once daily for 3 additional weeks. OUTCOMES: Preoperatively, the involved quadriceps produced 75% of the torque of the uninvolved side and demonstrated only 72.9% activation. At 3, 6, and 12 weeks after TKA, quadriceps torque was greater than the preoperative values of the involved side by 16%, 40% and 56%, respectively. Similarly, activation improved to 93.4%, 94.6%, and 93.5% at 3, 6, and 12 weeks after TKA. DISCUSSION: Mitigating quadriceps muscle weakness immediately after TKA using early NMES may improve functional outcomes, because quadriceps weakness has been associated with numerous functional limitations and an increased risk for falls. Despite presenting preoperatively with substantial quadriceps torque and activation deficits, the patient in this case demonstrated improvements in quadriceps function at all time points measured, all of which were superior to those reported in the literature.  The patient also made substantial improvements in functional outcomes, including the Knee Injury and Osteoarthritis Outcome Score (KOOS), 6-minute walk test, timed up and go (TUG) test, stair-climbing test, and the SF-36 Physical Component Score. Appropriately controlled clinical trials will be necessary to determine whether such favorable outcomes following TKA are specifically attributable to the addition of NMES to the rehabilitation program. 

J Orthop Sports Phys Ther. 2007, 37(7):364-371, published online 29 May 2007. doi:10.2519/jospt.2007.2541

KEY WORDS: electrical stimulation, knee replacement, muscle activation, rehabilitation