Improvement in upper leg muscle strength underlies beneficial effects of exercise therapy in knee osteoarthritis: secondary analysis from a randomised controlled trial.

OBJECTIVES: Although exercise therapy is effective for reducing pain and activity limitations in patients with knee osteoarthritis (OA), the underlying mechanisms are unclear. This study aimed to evaluate if improvements in neuromuscular factors (i.e. upper leg muscle strength and knee proprioception) underlie the beneficial effects of exercise therapy in patients with knee OA. DESIGN: Secondary analyses from a randomised controlled trial, with measurements at baseline, 6 weeks, 12 weeks and 38 weeks. SETTING: Rehabilitation centre. PARTICIPANTS: One hundred and fifty-nine patients diagnosed with knee OA. INTERVENTION: Exercise therapy. MAIN OUTCOME MEASURES: Changes in pain [numeric rating scale (NRS)] and activity limitations [Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function subscale and get-up-and-go test] during the study period. Independent variables were changes in upper leg muscle strength and knee joint proprioception (i.e. motion sense) during the study period. Longitudinal regression analyses (generalised estimating equation) were performed to analyse associations between changes in upper leg muscle strength and knee proprioception with changes in pain and activity limitations. RESULTS: Improved muscle strength was significantly associated with reductions in NRS pain {B coefficient -2.5 [95% confidence interval (CI) -3.7 to -1.4], meaning that every change of 1 unit of strength was linked to a change of -2.5 units of pain}, WOMAC physical function (-8.8, 95% CI -13.4 to -4.2) and get-up-and-go test (-1.7, 95% CI -2.4 to -1.0). Improved proprioception was not significantly associated with better outcomes of exercise therapy (P>0.05). CONCLUSIONS: Upper leg muscle strengthening is one of the mechanisms underlying the beneficial effects of exercise therapy in patients with knee OA.

Knee joint stabilization therapy in patients with osteoarthritis of the knee: a randomized, controlled trial.

OBJECTIVE: To investigate whether an exercise program, initially focusing on knee stabilization and subsequently on muscle strength and performance of daily activities is more effective than an exercise program focusing on muscle strength and performance of daily activities only, in reducing activity limitations in patients with knee osteoarthritis (OA) and instability of the knee joint. DESIGN: A single-blind, randomized, controlled trial involving 159 knee OA patients with self-reported and/or biomechanically assessed knee instability, randomly assigned to two treatment groups. Both groups received a supervised exercise program for 12 weeks, consisting of muscle strengthening exercises and training of daily activities, but only in the experimental group specific knee joint stabilization training was provided. Outcome measures included activity limitations (Western Ontario and McMaster Universities Osteoarthritis Index - WOMAC physical function, primary outcome), pain, global perceived effect and knee stability. RESULTS: Both treatment groups demonstrated large (∼20-40%) and clinically relevant reductions in activity limitations, pain and knee instability, which were sustained 6 months post-treatment. No differences in effectiveness between experimental and control treatment were found on WOMAC physical function (B (95% confidence interval - CI) = -0.01 (-2.58 to 2.57)) or secondary outcome measures, except for a higher global perceived effect in the experimental group (P = 0.04). CONCLUSIONS: Both exercise programs were highly effective in reducing activity limitations and pain and restoring knee stability in knee OA patients with instability of the knee. In knee OA patients suffering from knee instability, specific knee joint stabilization training, in addition to muscle strengthening and functional exercises, does not seem to have any additional value. Dutch Trial Register (NTR) registration number: NTR1475.

Proprioception in knee osteoarthritis: a narrative review.

OBJECTIVE: To give an overview of the literature on knee proprioception in knee osteoarthritis (OA) patients. METHOD: A literature search was performed and reviewed using the narrative approach. RESULTS: (1) Three presumed functions of knee proprioception have been described in the literature: protection against excessive movements, stabilization during static postures, and coordination of movements. (2) Proprioceptive accuracy can be measured in different ways; correlations between these methods are low. (3) Proprioceptive accuracy in knee OA patients seems to be impaired when compared to age-matched healthy controls. Unilateral knee OA patients may have impaired proprioceptive accuracy in both knees. (4) Causes of impaired proprioceptive accuracy in knee OA remain unknown. (5) There is currently no evidence for a role of impaired proprioceptive accuracy in the onset or progression of radiographic osteoarthritis (ROA). (6) Impaired proprioceptive accuracy could be a risk factor for progression (but not for onset) of both knee pain and activity limitations in knee OA patients. (7) Exercise therapy seems to be effective in improving proprioceptive accuracy in knee OA patients. CONCLUSIONS: Recent literature has shown that proprioceptive accuracy may play an important role in knee OA. However, this role needs to be further clarified. A new measurement protocol for knee proprioception needs to be developed. Systematic reviews focusing on the relationship between impaired proprioceptive accuracy, knee pain and activity limitations and on the effect of interventions (in particular exercise therapy) on proprioceptive accuracy in knee OA are required. Future studies focusing on causes of impaired proprioceptive accuracy in knee OA patients are also needed, taking into account that also the non-symptomatic knee may have proprioceptive impairments. Such future studies may also provide knowledge of mechanism underlying the impact of impaired proprioceptive accuracy on knee pain and activity limitations.

Natural course of knee osteoarthritis in middle-aged subjects with knee pain: 12-year follow-up using clinical and radiographic criteria.

OBJECTIVE: To explore the natural course of knee osteoarthritis (OA) in a middle-aged population with chronic knee pain. METHODS: A population-based sample of 143 subjects (mean age 45 (range 35-54), 44% women) with knee pain (>3 months) at inclusion was studied. Weight-bearing posteroanterior tibiofemoral (TF) radiographs were obtained at baseline and 12 years later, and classified according to Kellgren/Lawrence (K/L). Patellofemoral (PF) OA was determined at 5- and 12-years' follow-up using a skyline view and a cut-off point of <5 mm joint space width. The ACR clinical criteria were used at baseline. RESULTS: Seventy-six (53%) had no TF OA (K/L 0) at baseline, but 49 had clinical OA. Overall, 65/76 (86%) developed incident TF OA over 12 years (K/L >or=1): 44/49 (90%) of the subjects with clinical OA and 21/27 (78%) without clinical OA. Progression was found in 65/67 (97%) with TF OA at baseline. Of the 84 with no PF OA at the 5-year examination, 26 (31%) developed PF OA over 7 years. CONCLUSION: A majority of the subjects with chronic knee pain developed knee OA over 12 years. It is concluded that knee pain is often the first sign of knee OA.

The effect of eight weeks of exercise on knee adduction moment in early knee osteoarthritis--a pilot study.

OBJECTIVE: Reduced muscle function, causing greater knee joint load, is a potentially modifiable risk factor of knee osteoarthritis (OA). Exercise is an important treatment of knee OA, but the effect on joint load has not been determined. The aim of this study was to investigate the effect of exercise on knee adduction moment during one-leg rise and gait. DESIGN: Patients below age 65 with early signs of radiographic knee OA, from a population-based cohort on OA development, were invited to participate in the study. They defined their most symptomatic knee as the index knee. Knee adduction moment during one-leg rise from a stool (48cm), and during gait was assessed using a three-dimensional motion analysis system, before and after eight weeks of supervised exercise. RESULTS: Thirteen patients, seven women, mean age 54.5, 12/13 with Kellgren and Lawrence grade I or II, took part in the study. Peak knee adduction moment during one-leg rise was reduced by 0.08 (95% CI 0.01;0.16) Nm/kg, or 14%, for the index knee, and 0.05 (95% CI -0.04;0.14), or 8% for the opposite knee after eight weeks. The reductions in peak adduction moment during gait were smaller and not significant. CONCLUSIONS: This study indicates that peak knee adduction moment could be reduced by supervised, individualized exercise in middle-aged patients presenting early signs of knee osteoarthritis, suggesting further investigation of this area. Peak adduction moment during one-leg rise seems to be more sensitive to deviations and change than peak adduction moment during gait in this population.

Knee kinematics and kinetics during gait, step and hop in males with a 16 years old ACL injury compared with matched controls.

The objective of this study was to compare subjects who sustained an ACL injury during soccer 16 years ago with a control group with regard to knee kinematics and kinetics of gait, step activity and cross over hop. Secondly, in the injured subjects, the purpose was to study the impact on kinematics and kinetics of characteristics such as operative status, meniscal resection, being symptomatic, having knee extensor weakness and of having radiographic knee OA. Data from a 3-dimensional gait analysis system (VICON) were used to calculate kinetics and kinematics during gait, step activity and cross over hop of 12 male subjects who had an anterior cruciate ligament injury 16 years earlier. Twelve uninjured subjects matched for age, sex, BMI and activity level served as controls. No significant differences in knee kinematics and kinetics between the ACL group and the control group were found. The variability of some parameters of step and all parameters of hop activity was generally larger in the ACL injured subjects compared with the controls. The ACL injured subjects had a significantly worse clinical status compared with the controls. Reduced knee extension strength was associated with joint moment reductions especially during step activity and cross over hop. Despite a significantly worse clinical status, as determined by self-report and isokinetic strength testing, no significant differences were seen in knee joint kinetics and kinematics in an ACL injured group 16 years after injury compared with a matched control group. The variation was larger among the ACL injured subjects indicating the need for larger study groups in gait and movement analysis in long-term follow-up of ACL injury.

Reduced functional performance in the lower extremity predicted radiographic knee osteoarthritis five years later.

BACKGROUND: Reduced quadriceps strength is an early finding in subjects with knee osteoarthritis, but it is not clear whether it is a cause or a consequence of knee osteoarthritis. OBJECTIVE: To determine whether reduced functional performance in the lower extremity predicts the incidence or progression of radiographic knee osteoarthritis. DESIGN: Prospective, epidemiological, population based cohort study. PATIENTS: 148 subjects (62 women), aged 35-54 (mean 44.8), with chronic knee pain from a population based cohort. MEASUREMENTS: Predictors analysed were age, sex, body mass index, baseline knee pain, and three tests of lower extremity functional performance: maximum number of one-leg rises from sitting, time spent walking 300 m, and timed standing on one leg. Weightbearing tibiofemoral knee radiographs were obtained at baseline and after 5 years (median 5.1, range 4.2-6.1), and classified according to Kellgren and Lawrence as no osteoarthritis (Kellgren and Lawrence = 0, n = 94) or prevalent osteoarthritis (Kellgren and Lawrence >/=1, n = 54). RESULTS: Fewer one-leg rises (median 17 v 25) predicted incident radiographic osteoarthritis five years later (OR 2.6, 95% CI 1.1 to 6.0). The association remained significant after controlling for age, sex, body mass index, and pain. No significant predictor of radiographic progression in the group with prevalent osteoarthritis was found. CONCLUSION: Reduced functional performance in the lower extremity predicted development of radiographic knee osteoarthritis 5 years later among people aged 35-55 with chronic knee pain and normal radiographs at baseline. These findings suggest that a test of one-leg rises may be useful, and interventions aimed at improving functional performance may be protective against development of knee osteoarthritis.