The role of foot and ankle assessment of patients with lower limb osteoarthritis
Introduction
Osteoarthritis is a major public health problem that occurs in up to 25% of people over 65 years of age [1]. The World Health Organization estimates that osteoarthritis is one of the major causes of impaired function which reduces health worldwide [2]. The aetiology of osteoarthritis is complex, embracing genetics, biochemistry and biomechanics [3]. Biomechanical factors play a central role [4], and it has been suggested that investigating any underlying biomechanical abnormality should be a priority for the conservative management of osteoarthritis [5].
Lower limb weight-bearing joints are particularly susceptible to biomechanical stress [3]. This may be specific to the joint site and even joint compartment [6]. In medial compartment osteoarthritis of the knee, the lesion is localised to the medial compartment within the joint and progresses within this area, suggesting a strong biomechanical contribution [7]. Similarly, in osteoarthritis of the hip, superolateral wear of the acetabulum has been identified as a local mechanical factor [8]. Biomechanical changes that occur in the deep chondral layers and subchondral bone seem to be particularly important [9], [10]. Eckhoff argues that rotation is the force leading to asymmetry of pressure and altered patterns of shear stresses with the potential to cause degeneration of the deep chondral layers [11].
The rotary stresses experienced by the weight-bearing leg are related to the amount of foot supination or pronation during the stance phase of the gait cycle [12]. The synchronous actions of the knee, hip and subtalar joint during the contact and midstance phases of gait are interdependent motions, and the rotation of the tibia and femur are obligatory actions for normal kinetics of both joints [13]. Where the timing of supination and pronation are not synchronous with the rotational elements of lower limb gait, this may result in a rotatory torque at the knee or hip which may influence the loading of deep chondral layers of cartilage in these joints.
Sports medicine has a long tradition of linking foot posture and ankle range of movement to lower limb musculoskeletal injuries [13], [14]. Foot posture and lower limb osteoarthritis may also be linked [3], [15]. A previous study by Reilly et al. that compared 60 people with medial compartment osteoarthritis of the knee, 60 people with osteoarthritis of the hip and 60 healthy age-matched controls demonstrated significant differences in foot type between these three groups [16]. In this study, the limited ankle dorsiflexion scores and high arches of individuals with osteoarthritis of the hip contrasted with the good range of dorsiflexion and flat feet of those with medial compartment osteoarthritis of the knee, and these two groups differed from the control group of healthy subjects [16].
Guidelines for managing osteoarthritis issued by the National Centre for Clinical Excellence in 2008 recommend orthotics and footwear advice as well as exercise and physiotherapy [17], which indicates that the biomechanics of gait are considered relevant. A comprehensive assessment of foot posture could be important, therefore, for understanding the development of osteoarthritis and its conservative management. At present, detailed examination of foot posture is not a routine part of a physiotherapy assessment of patients with osteoarthritis of the hip or medial compartment osteoarthritis of the knee. The ideal foot posture is one which demonstrates, in relaxed stance, a neutral position with no evidence of either over-supination or over-pronation. Physiotherapists may use goniometry to measure the range of movement of the talocrural joint, but this assessment only provides limited information about pronation and supination. Measurements of calcaneal angle or navicular height using a plumb line, ruler or protractor provide detailed information about alignment, but can be time consuming and require considerable skill to collect accurately [16]. Their utility in a busy physiotherapy outpatient department is questionable.
The development of the Foot Posture Index (FPI) by Redmond et al. in 2006 addressed the need for a diagnostic clinical tool. It measures foot posture in three planes and two anatomical segments [18]. The FPI has been explored in a population of healthy adult volunteers aged 18 to 57 years, and has been shown to be reliable and to have construct validity [18], [19], [20]. However, to date, the FPI has not been widely used by physiotherapists with patients who have osteoarthritis of the hip or knee.
Section snippets
Objectives
The primary aim of this study was to assess the utility of the FPI, to see if it can effectively describe the foot posture of people with osteoarthritis of the hip and medial compartment osteoarthritis of the knee compared with healthy age-matched controls. In addition, this study explored the relationship between foot posture and talocural dorsiflexion.
Design
A cross-sectional observational study was conducted at a specialist orthopaedic hospital. Measurements of foot posture and dorsiflexion were taken on a single occasion by a research physiotherapist (KR) in an outpatient clinic. Approval was gained from the Mid and South Buckinghamshire Local Research Ethics Committee, (REC No. 06/Q1607/1) and the Hospital Research Committee; all participants gave written informed consent.
Setting
Consecutive patients awaiting elective hip or knee arthroplasty were sent
Results
Table 1 describes the baseline characteristics of the study population. At baseline, the groups did not differ in terms of age or gender. FPI and dorsiflexion scores were significantly different between the three groups (P < 0.001) (Table 2). The Mann–Whitney U-test revealed significant differences in FPI and dorsiflexion between each of the three groups (P < 0.001). Participants with osteoarthritis of the hip had a median FPI score of −4.5, indicating a supinated foot, and a mean −2 degrees of
Discussion
The FPI is an easy tool to use in a clinical setting and yields a numerical score for foot posture. As it comprises both summary and composite scores, it gives a comprehensive description of foot posture. This can be used to assess whether the foot is pronated or supinated, and to identify any particular problem area. The findings of the present study show that it is sufficiently sensitive to demonstrate the differences between patients with osteoarthritis of the hip, patients with medial
Study limitations
The measurements in this trial were taken by a single physiotherapist. It was not possible to blind her to the site of osteoarthritis of the patients, and therefore the results may be subject to bias. In addition, the sample size calculation was carried out retrospectively. Although patients were not excluded on grounds of ethnicity, the population was Caucasion and racial differences in gait and foot type have been considered significant by previous authors [36], [37], [38]. A further
Conclusions
From the results of this study, the use of the FPI is recommended in the clinical assessment of patients with lower limb osteoarthritis. Dorsiflexion measurement on its own may indicate that further assessment is necessary, but the FPI documents clinical features in detail. The FPI can also be utilised to assess the results of therapeutic modifications, such as foot orthoses, or treatment programmes of muscle strengthening, stretching and gait re-training.
Developing inexpensive, non-invasive
References (38)
- et al.
A review on the mechanical quality of articular cartilage—implications for the diagnosis of osteoarthritis
Clin Biomech
(2006) Effect of limb malrotation on malalignment and osteoarthritis
Orthop Clin N Am
(1994)- et al.
Development and validation of a novel rating system for scoring standing foot posture: the foot posture index
Clin Biomech
(2006) - et al.
The foot posture index: Rasch analysis of a novel, foot specific outcome measure
Arch Phys Med Rehabil
(2007) - et al.
Normative data for passive ankle plantarflexion–dorsiflexion flexibility
Clin Biomech
(2001) - et al.
Weight bearing ankle dorsiflexion range of motion in idiopathic pes cavus compared to normal and pes planus feet
Foot
(2005) - et al.
A systematic review of lateral wedge orthotics—how useful are they in the management of medial compartment osteoarthritis
Knee
(2006) - et al.
A comparison of the gaits of Chinese and Caucasian women with particular reference to their heelstrike transients
Clin Biomech
(2003) - et al.
The footprint ratio as a predictor of pes planus: a study of indigenous Malawians
J Foot Ankle Surg
(2002) - et al.
The shape of things to come: chondrocytes and osteoarthritis
Clin Invest Med
(2003)