Neuromuscular function after arthroscopic partial meniscectomy.
BACKGROUND
Quadriceps muscle strength, which is essential for the function and stability of the knee, has been found to be impaired even years after arthroscopic partial meniscectomy. However, the neuromuscular alterations that could account for such muscle weakness remain unclear.


OBJECTIVE
We investigated (1) the side-to-side asymmetries in quadriceps muscle strength 6 months after arthroscopic partial meniscectomy, (2) the physiologic mechanisms (neural versus muscular) underlying muscle weakness, and (3) the impact of quadriceps weakness on muscle control at submaximal force levels.


METHODS
We tested 14 volunteers (10 men, four women) with an average age of 44 +/- 9 years (range, 24-59 years) at 6 +/- 1 months after unilateral medial arthroscopic partial meniscectomy. We measured maximal voluntary strength and muscle activation during isometric, concentric, and eccentric contractions using isokinetic dynamometry and surface EMG, respectively. We assessed vastus lateralis muscle size and architecture using ultrasonography. We measured muscle control at submaximal force levels with a repositioning test (knee proprioception) and a low-force target-tracking task (steadiness, accuracy).


RESULTS
Isometric and concentric quadriceps strength and vastus lateralis EMG activity were lower on the involved than on the uninvolved side. Muscle architecture and muscle control did not differ between the involved and uninvolved sides.


CONCLUSIONS
Our results showed quadriceps weakness exists 6 months after arthroscopic partial meniscectomy. As suggested by the EMG results, this is likely attributable to neural impairments (activation failure) that affect muscle control at maximal but not submaximal force outputs.


METHODS
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
Glatthorn
Julia F
JF
Neuromuscular Research Laboratory, Schulthess Clinic, Lengghalde 2, 8008 Zurich, Switzerland.
Berendts
Andreas M
AM
Bizzini
Mario
M
Munzinger
Urs
U
Maffiuletti
Nicola A
NA
D000328:Adult; D001182:Arthroscopy / Q000009:adverse effects* / Q000379:methods; D003937:Diagnosis, Differential; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007718:Knee Injuries / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008592:Menisci, Tibial / Q000601:surgery*; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018908:Muscle Weakness / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000294:innervation / Q000502:physiology*; D020127:Recovery of Function / Q000502:physiology*; D000070600:Tibial Meniscus Injuries; D055815:Young Adult