Quadriceps inhibition following arthroscopy in patients with anterior knee pain

OBJECTIVES: This study was aimed at investigating muscle strength and quadriceps inhibition in patients with unilateral anterior knee pain syndrome. DESIGN: Functional assessments were made before an arthroscopic knee surgery and 6 weeks and 6 months following the surgical intervention. BACKGROUND: Traumatic knee injuries have been associated with severe muscle inhibition of the knee extensor muscles. Muscle inhibition is a serious hindrance in the rehabilitation process and prevents full functional recovery of the affected joint. METHODS: 30 patients participated in the study. Isometric quadriceps strength was measured using a KinCom dynamometer. Muscle inhibition was assessed using the interpolated twitch technique which requires applying a single electrical twitch to the femoral nerve during a maximal isometric knee extensor contraction. Pain was assessed with a 100 mm visual analogue pain scale. RESULTS: Pre-surgery, substantial muscle inhibition and pain was observed in the affected leg compared with the contralateral leg. Over the 6 month period there was a decrease in pain and muscle inhibition, although the decrease in muscle inhibition failed to reach statistical significance. Muscle strength showed a decrease 6 weeks post-surgery followed by an increase 6 months following surgery compared with pre-surgical values. CONCLUSIONS: The arthroscopic intervention was successful in reducing pain in patients with unilateral anterior knee pain syndrome. However, muscle inhibition was still substantial 6 months following surgery and was significantly higher in the affected and contralateral limb than in normal subjects.