Reachout Orthopedics - Issue 2

Foot OA has recently been found to be highly prevalent and disabling, yet in contrast to hand, knee and hip OA, there is little research in the field to guide clinical management. This paper provides a review of the assessment and non-surgical treatment of foot and ankle OA for clinical practice. Where evidence-based information specifically related to the foot, ankle or individual foot joints is lacking, relevant clinical research from other joints that may be generalised to the foot/ankle is provided. Epidemiology and Impact of Foot and Ankle Osteoarthritis (OA) Historically, the knee has been considered to be the most commonly affected weight bearing region, with a reported prevalence of 7.6–16.4% [1]. However, recent research revealed the population prevalence of symptomatic radiographic foot OA was 16.7% [5], suggesting it may be as common as knee OA. Within the foot, the first metatarsophalangeal joint (MTPJ) is the most commonly affected joint, with a prevalence rate slightly higher than hip OA at 7.8% [5]. Midfoot joints are also commonly affected, including the second cuneiform- metatarsal joint (6.8%), talo-navicular joint (5.8%), naviculo-cunieform joint (5.2%), and first cuneiform-metatarsal joint (3.9%) [5]. If these individual joints are considered as a single midfoot complex, as they typically are for clinical management [6], the prevalence of symptomatic radiographic midfoot OA is reported to be 12.0% [7]. The prevalence of symptomatic radiographic OA of the ankle has also been reported to be 3.4% [8], and it has been suggested that the majority of these are post-traumatic [9]. Foot and ankleOAare highly debilitating. An overwhelming 69% of people with symptomatic radiographic foot OA report experiencing disabling foot pain [5], and this pain has been shown to result in functional limitations and significant impairments in measures of balance, strength and locomotor ability [10]. Disabling foot pain is a significant and independent risk factor for falls [11], and foot OA, particularly of the first MTPJ, also leads to significant reductions in all domains of the foot health status questionnaire, and the physical and social function subscales of the Short Form 36 questionnaire [12]. It has also been shown to worsen symptoms at other joints, and to increase the risk of developing OA more proximally in people aged over 45 years. Specifically, a recent large cohort study found that the presence of foot/ ankle pain significantly reduced health and physical function in people with knee OA [13]. Subsequent analyses from this cohort found that foot/ankle pain substantially increased the risk of developing symptomatic radiographic knee OA within the subsequent 4 years [14], and increased the risk of worsening knee pain in those with existing knee OA [15]. Foot and ankle problems are a common cause for consulting a general practitioner [16]. In fact, up to 32%of peoplewith foot pain report consulting their general practitioner— more than those with musculoskeletal pain at any other site [17]. The adverse effects on health, physical function and quality of life from foot and ankle OA have also been shown to impact on working ability, with foot OA reported to be the only OA site significantly associated with employment reduction in males [18]. This is important given half of people with OA are of working age [19]. Foot and Ankle OA Phenotypes The median number of foot joints affected by OA in people aged over 65 years is four [20], suggesting that the typical presentation of foot OA is as a multi-joint disease pattern. This was confirmed in a recent population- based study which used latent class analysis to investigate potential foot OA phenotypes. Outcomes showed two distinct foot OA phenotypes: a polyarticular form of foot OA that included a clustering of midfoot joints, and isolated OA of the first MTPJ [21]. Both subgroups were significantly older than people with no or minimal OA, whilst the polyarticular group were also more likely to be female, and to have more persistent and severe pain, greater functional limitation, a higher body mass index (BMI) and increased presence of nodal hand OA. The study also found that the disease was more prevalent in one foot only; however, when foot OA was bilateral, there was a strong association for a symmetrical distribution [21]. A high level of symmetry is also common in the polyarticular form of hand OA [22]. Assessment Clinical Assessment Evidence-based recommendations for the clinical diagnosis of OA currently exist for the knee [23], with a diagnosis made by three signs on examination (crepitus, restricted movement and bony enlargement) and symp- toms (knee pain, short-lived morning stiffness and functional limitation). Despite the com- parable prevalence, there are currently very few agreed guidelines for the clinical diagnosis of foot or ankle OA, which limits our ability to advance the development of interventions and provide targeted treatment. A variety of foot and ankle assessment measures have been adopted by a number of OA-linked prospective cohort studies. The Johnston County Osteoarthritis Project and the Framingham Foot Study included a pictorial atlas of common foot disorders, foot structure (measured with the Arch Index), and assessment of hallux valgus and hallux rigidus [24, 25], whilst the Chingford 1000 Women Study used the International Musculoskeletal Foot and Ankle Assessment [26]. Although a number of measures have been validated against foot disorders [27], all have yet to be validated against OA-related outcomes. CASF (Clinical Assessment Study of the Foot) derived a brief collection of static assessments from pre-study consensus work, including measures of foot posture, range of motion, observation and palpation [28]. None of these were able to discriminate between individuals with and without structural radiographic midfoot changes [29]. However, assessments including dorsal hallux and first MTPJ pain, hallux valgus, first interphalangeal joint hyperextension, keratotic lesions of the hallux and first MTPJ, decreased first MTPJ dorsiflexion, ankle/subtalar joint eversion, and ankle joint dorsiflexion range of motion were all significantly associated with radiographic Foot OA has recently been found to be highly prevalent and disabling, yet in contrast to hand, knee and hip OA, there is little research in the field to guide clinical management. 19 reachOut Orthopedics