Restricted joint mobility, especially in flexion of the knee and extension and external rotation of the hip, appears to be an important determinant of disability in patients with OA.

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

BackgroundKnee Osteoarthritis (KOA) is a heterogeneous pathology characterized by a complex and multifactorial nature. It has been hypothesised that these differences are due to the existence of underlying phenotypes representing different mechanisms of the disease.MethodsThe aim of this study is to identify the current evidence for the existence of groups of variables which point towards the existence of distinct clinical phenotypes in the KOA population. A systematic literature search in PubMed was conducted. Only original articles were selected if they aimed to identify phenotypes of patients aged 18 years or older with KOA. The methodological quality of the studies was independently assessed by two reviewers and qualitative synthesis of the evidence was performed. Strong evidence for existence of specific phenotypes was considered present if the phenotype was supported by at least two high-quality studies.ResultsA total of 24 studies were included. Through qualitative synthesis of evidence, six main sets of variables proposing the existence of six phenotypes were identified: 1) chronic pain in which central mechanisms (e.g. central sensitisation) are prominent; 2) inflammatory (high levels of inflammatory biomarkers); 3) metabolic syndrome (high prevalence of obesity, diabetes and other metabolic disturbances); 4) Bone and cartilage metabolism (alteration in local tissue metabolism); 5) mechanical overload characterised primarily by varus malalignment and medial compartment disease; and 6) minimal joint disease characterised as minor clinical symptoms with slow progression over time.ConclusionsThis study identified six distinct groups of variables which should be explored in attempts to better define clinical phenotypes in the KOA population.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-016-1286-2) contains supplementary material, which is available to authorized users.

Objective. To test the hypotheses that poor knee joint proprioception is related to limitations in functional ability, and poor proprioception aggravates the impact of muscle weakness on limitations in functional ability in osteoarthritis (OA) of the knee. Methods. Sixty-three patients with symptomatic OA of the knee were tested. Proprioceptive acuity was assessed by establishing the joint motion detection threshold (JMDT) in the anteroposterior direction. Muscle strength was measured using a computer-driven isokinetic dynamometer. Functional ability was assessed by the 100-meter walking test, the Get Up and Go (GUG) test, and the Western Ontario and McMaster Universities Osteoarthritis Index physical function (WOMAC-PF) questionnaire. Correlation analyses were performed to assess the relationship between proprioception, muscle strength, and functional ability. Regression analyses were performed to assess the impact of proprioception on the relationship between muscle strength and functional ability. Results. Poor proprioception (high JMDT) was related to more limitation in functional ability (walking time r ‫؍‬ 0.30, P < 0.05; GUG time r ‫؍‬ 0.30, P < 0.05; WOMAC-PF r ‫؍‬ 0.26, P <0.05). In regression analyses, the interaction between proprioception and muscle strength was significantly related to functional ability (walking time, P < 0.001 and GUG time, P < 0.001) but not to WOMAC-PF score (P ‫؍‬ 0.625). In patients with poor proprioception, reduction of muscle strength was associated with more severe deterioration of functional ability than in patients with accurate proprioception. Conclusion. Patients with poor proprioception show more limitation in functional ability, but this relationship is rather weak. In patients with poor proprioception, muscle weakness has a stronger impact on limitations in functional ability than in patients with accurate proprioception.

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.