| The overall goal was to determine the etiological factors of quadriceps weakness and its relationship to function in individuals with Grade IV knee osteoarthritis (OA) and total knee arthroplasty (TKA) and to determine the effectiveness of interventions targeting muscle strength, activation, and atrophy after TKA.; The first series of studies were performed to determine the extent of impairment acquired as a result of knee OA. First, the OA group (N=195) exhibited significant impairments in pain, strength, activation, and function compared to the healthy group (N=34). Pain strongly influenced self-reported function whereas quadriceps strength significantly determined functional performance. Second, gender differences in disease impact were measured. Perceived functional ability was similar between men (N=78) and women (N=72), despite women exhibiting larger impairments in strength and function; this indicates greater disease severity at the time of TKA. Third, the extent of quadriceps weakness was measured using a burst superimposition technique to obtain muscle activation and magnetic resonance imaging (NM) to determine muscle size (N=116). The symptomatic limb was significantly weaker, smaller, and had larger activation deficits compared to the asymptomatic limb. Activation had the greatest influence on quadriceps weakness in the symptomatic limb.; Strength and function were then assessed after TKA (N=106) to determine whether OA-related impairments are resolved with TKA and rehabilitation. Significant improvement in self-reported function, functional performance, quadriceps strength, and activation occurred over the first postoperative year although, strength and function remained below healthy individuals (N=37). Second, MRI and strength testing revealed activation deficits were larger in the non-surgical limb and muscle atrophy was greater in the surgical limb (N=39). Activation levels largely determined strength in inhibited muscles. Lastly, a case report demonstrated a 6-week neuromuscular electrical stimulation (NMES) program combined with progressive, resistance exercises can be successful in reversing chronic quadriceps strength and activation impairments.; In summary, quadriceps weakness is a primary impairment limiting function in persons with knee OA and TKA. The ineffectiveness of conventional treatment to reverse impairments may reduce quality of life and predispose individuals to greater long-term decline. The success of alternative treatment modalities (i.e. NMES) in reversing activation deficits warrants continued research. |
