Knee function reduced following surgery due to decreased quadriceps strength

Meniscectomy, the surgical removal of all or part of the meniscus in the knee, is a common treatment that reduces pain and improves knee function. However, limitations in knee function have been shown in both short-term and long-term studies for reasons that have been unclear. A new study published in the December 2006 issue of Arthritis Care & Research (http://www.interscience.wiley.com/journal/arthritiscare) examined muscle strength, performance, and outcomes perceived by patients several years after undergoing a meniscectomy.

Led by Ylva B. Ericsson, PT, MSc, of Malmö University Hospital in Malmö, Sweden and Lund University in Lund, Sweden, the study included 45 patients aged 38-50 years old who had surgery because of meniscus tears between one and six years prior to the start of the study. Patients were tested for muscle strength and functional performance and were given a questionnaire, the Knee Injury and Osteoarthritis Outcome Score (KOOS), which measures pain, function in daily activities and sports, and knee-related quality of life. The results showed that muscle strength and functional performance were lower for the leg that was operated on compared to the leg that was not operated on. In addition, patients reported symptoms and functional limitations on the KOOS, scoring lower in all areas compared to healthy control patients. Quadriceps muscle strength corresponded to KOOS scores.

This is the first study to show that in patients undergoing knee surgery for a non-traumatic meniscus tear, muscle strength and performance is lower in the leg that was operated on than the other leg four years after surgery. Although lower muscle strength a few months following surgery had been previously reported, little emphasis has been placed on restoring strength. "Meniscectomy patients are usually prescribed a home exercise program, but supervised physical therapy is not considered necessary," the authors note.

In addition, few studies have examined the relationship between strength deficits and function, the authors point out. Although isokinetic muscle strength can be quantified, these tests do not take into account other muscular aspects like timing and coordination. Functional performance tests attempt to mimic natural movements, but they are complex because they involve multiple joints and muscle groups. "In the present study, the association between the quadriceps strength deficits and self-reported symptoms and function suggests a close relationship between muscle strength and functional limitations in middle-aged patients who have undergone meniscectomy," the authors state. They add that the relationship between the quadriceps strength ratio and the 1-leg rising test ratio (in which the seated patient was asked to rise on one leg as many times as possible in succession) may indicate that decreased quads strength contributes to limited knee function.

Muscle impairment may also contribute to the feeling of instability that meniscectomy patients frequently mention and may play a role in osteoarthritis. The authors note that even the 9% quads deficit found in the present study four years after surgery may prove significant in the context of a disease that develops over 10 to 15 years. They conclude that "this relative quadriceps weakness significantly affects objective and self-reported knee function, pain, and quality of life, indicating the importance of restoring muscle function after meniscectomy in middle-aged patients."

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Article: "Muscle Strength, Functional Performance, and Self-Reported Outcomes Four Years After Arthroscopic Partial Meniscectomy in Middle-Aged Patients," Ylva B. Ericsson, Ewa M. Roos, Leif Dahlberg, Arthritis Care & Research, December 2006; (DOI: 10.1002/art.22346).


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