Relation between isokinetic muscle strength and functional capacity in recreational athletes with chondromalacia patellae.(Original Article)

Br J Sports Med 2003;37:475-479

Objectives: To investigate the effects of isokinetic exercise on pain and functional test scores of recreational athletes with chondromalacia patellae (CMP) and to examine the correlation between isokinetic parameters and functional tests or pain score.

Methods: The functional ability of 30 recreational athletes with unilateral CMP was evaluated using six different tests. Pain scores were assessed during daily activities before and after the treatment protocol. Isokinetic exercise sessions were carried out at angular velocities of 60[degrees]/s (25-90[degrees] range of flexion) and 180[degrees]/s (full range). These sessions were repeated three times a week for six weeks.

Results: Quadriceps and hamstring peak torque, total work, and endurance ratios had improved significantly after the treatment, as did the functional parameters and pain scores. There was a poor correlation between the extensor endurance ratio and one leg standing test. A moderate correlation between the visual analogue scale and the extensor endurance ratio or flexion endurance ratio was also found.

Conclusions: The isokinetic exercise programme used in this study had a positive effect on muscle strength, pain score, and functional ability of knees with CMP. The improvement in the functional capacity did not correlate with the isokinetic parameters.

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The knee joint is often exposed to sports injury because of its function in various activities and its limited motion. Patellofemoral disorders are some of the most commonly treated conditions. Anterior knee pain may result from articular cartilage damage, retinacular tightness, patellofemoral malalignment, localised trauma, or inflammation of periarticular soft tissue. A systematic approach to the assessment of anterior knee pain is critical for accurate diagnosis and initiation of the correct treatment. (1-3) Chondromalacia patellae (CMP) is evaluated in cases of patellofemoral pain syndrome. (4) The term is used to describe pathological lesions of the patellar articular cartilage found at magnetic resonance imaging, arthroscopy, or arthrotomy. (5) The patellofemoral joint is a complex articulation because of its dependence on both dynamic and static restraints for stability. (6 7)

Patellofemoral pain is typically activity induced and aggravated by actions that increase patellofemoral compressive forces, such as ascending and descending stairs, inclined walking, squatting, and prolonged sitting. (8)

CMP and other patellofemoral disorders are often accompanied by patellofemoral instability. This can be simply a reflex inhibition of the quadriceps muscle secondary to pain. (8) In this respect, a significant correlation between isokinetic parameters or pain and functional tests would be expected. However, the relation between functional performance tests and isokinetic muscle strength is controversial, and the general opinion is that there is poor correlation.

Patellofemoral instability is not only related to mechanical factors but also to proprioceptive deficits caused by mechanoreceptor injury. (8) Rehabilitation must therefore focus on restoring the proprioceptive mechanism by enhancing cognitive appreciation of the respective joint relative to position and movement, and by providing muscular stabilisation of the joint in the absence of structural restraints. Irrgang and Pezzullo (9) have stated that exercise has a positive influence on articular nutrition because of compression of the articular surfaces and decreased oedema. Thus, when developing an exercise programme, it is important to keep in mind the biomechanics of the joint and the possible deleterious effects of inappropriate exercise. The patellofemoral compressive forces are reduced as the testing speed is increased. (10)

It has been shown that isokinetic exercises can improve muscle endurance and power. The aim of this study was to determine the effects of isokinetic training on the muscular strength and endurance, pain, and functional status of recreational athletes with CMP. We investigated the relations between the isokinetic parameters, functional capacity, and pain scores.

MATERIALS AND METHODS

Subjects

Thirty male recreational athletes (mean (SD) age 24 (4) years, height 173 (5) cm, weight 73.0 (6.2) kg, body fat percentage 22.1 (4.3)) were recruited. All subjects had unilateral CMP diagnosed by magnetic resonance imaging. They had no contralateral lower extremity pathologies, neurological problems, or other conditions that could be aggravated by the testing protocol or could confound the test results. None had undertaken an exercise programme within the preceding three months. They were requested to refrain from unusual activities or vigorous exercise for 24 …