Proprioception plays an important role in the complex mechanism of joint control. Proprioceptive training is popularly applied as preventive or rehabilitative exercise method in various sports and rehabilitation settings. The primary purpose of this narrative review is to evaluate the current literature and to provide further insight about proprioception. The objective is to answer few important questions: • What are the factors affecting it? • How to evaluate proprioception? • What are the tools and technique required for the assessment? • How to train, improve, and progress in proprioceptive training? This evidence based study helps to guide rehabilitation professionals in selecting appropriate, effective strategies when managing issues related to position sense. Postural balance and its sensory motor correlates in 75-year-old men and women: A cross-national comparative study. J Gerontol A Biol Sci Med Sci 51(2): M53-M63. 6. Barrack RL, Skinner HB, Cook SD, Haddad RJ (1983) Effect of articular disease and total knee arthroplasty on knee joint position sense. J Neurophysiol 50(3): 684-687. 7. Hassan BS, Mockett S, Doherty M (2001) Static postural sway, proprioception, and maximal voluntary quadriceps contraction in patients with knee osteoarthritis and normal control subjects. Ann

Objective. To identify subgroups or phenotypes of knee osteoarthritis (OA) patients based on similarities of clinically relevant patient characteristics, and to compare clinical outcomes of these phenotypes. Methods. Data from 842 knee OA patients of the Osteoarthritis Initiative were used. A cluster analysis method was performed, in which clusters were formed based on similarities in 4 clinically relevant, easily available variables: severity of radiographic OA, lower extremity muscle strength, body mass index, and depression. Univariable and multivariable regression analyses were used to compare phenotypes on clinical outcomes (pain and activity limitations), taking into account possible confounders. Results. Five phenotypes of knee OA patients were identified: "minimal joint disease phenotype," "strong muscle phenotype," "nonobese and weak muscle phenotype," "obese and weak muscle phenotype," and "depressive phenotype." The "depressive phenotype" and "obese and weak muscle phenotype" showed higher pain levels and more severe activity limitations than the other 3 phenotypes. Conclusion. Five phenotypes based on clinically relevant patient characteristics can be identified in the heterogeneous population of knee OA patients. These phenotypes showed different clinical outcomes. Interventions may need to be tailored to these clinical phenotypes.

Objective. To determine whether muscle strength, proprioceptive accuracy, and laxity are associated with self-reported knee instability in a large cohort of knee osteoarthritis (OA) patients, and to investigate whether muscle strength may compensate for impairment in proprioceptive accuracy or laxity, in order to maintain knee stability. Methods. Data from 283 knee OA patients from the Amsterdam Osteoarthritis cohort were used. Univariable and multivariable logistic regression analyses were performed to assess the association between muscle strength, proprioceptive accuracy (motion sense), frontal plane varus-valgus laxity, and self-reported knee instability. Additionally, effect modification between muscle strength and proprioceptive accuracy and between muscle strength and laxity was determined. Results. Self-reported knee instability was present in 67% of the knee OA patients and mainly occurred during walking. Lower muscle strength was significantly associated with the presence of self-reported knee instability, even after adjusting for relevant confounding. Impaired proprioceptive accuracy and high laxity were not associated with self-reported knee instability. No effect modification between muscle strength and proprioceptive accuracy or laxity was found. Conclusion. Lower muscle strength is strongly associated with self-reported knee instability in knee OA patients, while impairments in proprioceptive accuracy and laxity are not. A compensatory role of muscle strength for impaired proprioceptive accuracy or high laxity, in order to stabilize the knee, could not be demonstrated.

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.

Based on the 5-year course of activity limitations, we identified homogeneous subgroups of knee OA patients with good, moderate or poor outcome. Characteristics of these subgroups were consistent with existing knowledge on prognostic factors regarding activity limitations, which supports the validity of this classification.

Objective. To evaluate the efficacy on physical functioning and safety of tailored exercise therapy in patients with knee osteoarthritis (OA) and comorbidities. Methods. In a randomized controlled trial, 126 participants were included with a clinical diagnosis of knee OA and at least 1 of the following target comorbidities: coronary disease, heart failure, type 2 diabetes mellitus, chronic obstructive pulmonary disease, or obesity (body mass index ‡30 kg/m 2 ), with severity score ‡2 on the Cumulative Illness Rating Scale. The intervention group received a 20-week, individualized, comorbidity-adapted exercise program consisting of aerobic and strength training and training of daily activities. The control group received their current medical care for knee OA and were placed on a waiting list for exercise therapy. Primary outcome measures were the Western Ontario and McMaster Universities Osteoarthritis Index, subscale physical functioning (WOMAC-pf), and the 6-minute walk test (6MWT). Measurements were performed at baseline, after 20 weeks (directly posttreatment), and at 3 months posttreatment. Results. Statistically significant physical functioning differences over time were found between the intervention and control group (WOMAC: B 5 27.43 [95% confidence interval (95% CI) 29.99, 24.87], P < 0.001; and 6MWT: B 5 34.16 [95% CI 17.68, 50.64], P < 0.001) in favor of the intervention group. At 3 months followup, the mean improvements in the intervention group were 33% on the WOMAC scale and 15% on the 6MWT. These improvements are of clinical relevance. No serious adverse events occurred during the intervention. Conclusion. This is the first study showing that tailored exercise therapy is efficacious in improving physical functioning and safe in patients with knee OA and severe comorbidities.

Objective. To systematically summarize the literature on the course of pain in patients with knee osteoarthritis (OA), prognostic factors that predict deterioration of pain, the course of physical functioning, and prognostic factors that predict deterioration of physical functioning in persons with knee OA. Methods. A search was conducted in PubMed, CINAHL, Embase, Psych-INFO, and SPORTDiscus up to January 2014. A meta-analysis and a qualitative data synthesis were performed. Results. Of the 58 studies included, 39 were of high quality. High heterogeneity across studies (I 2 >90%) and within study populations (reflected by large SDs of change scores) was found. Therefore, the course of pain and physical functioning was interpreted to be indistinct. We found strong evidence for a number of prognostic factors predicting deterioration in pain (e.g., higher knee pain at baseline, bilateral knee symptoms, and depressive symptoms). We also found strong evidence for a number of prognostic factors predicting deterioration in physical functioning (e.g., worsening in radiographic OA, worsening of knee pain, lower knee extension muscle strength, lower walking speed, and higher comorbidity count). Conclusion. Because of high heterogeneity across studies and within study populations, no conclusions can be drawn with regard to the course of pain and physical functioning. These findings support current research efforts to define subgroups or phenotypes within knee OA populations. Strong evidence was found for knee characteristics, clinical factors, and psychosocial factors as prognostics of deterioration of pain and physical functioning.

Among patients with knee OA, five phenotypes were identified based on four clinical characteristics. To a high degree, the results are a replication of earlier findings in the OA Initiative, indicating that these five phenotypes seem a stable, valid, and clinically relevant finding.