Foot problems such as synovitis, limited range of motion, malalignment and deformity have been reported in over 90% of children with juvenile idiopathic arthritis (JIA), generally increasing in severity with age, disease duration and in those with polyarticular disease (Spraul & Koenning 1994). Foot pain, deformity and impaired function are persistent problems even in those children optimally managed on DMARD and biologic therapy (Hendry et al 2008). Synovitis in the ankle and rearfoot joint occurs in approximately one-third of patients across all disease subtypes and is associated with limited ankle range of motion, pronated rearfoot and midfoot joints, and weakness of the ankle dorsiflexors/plantarflexors (Brostrom et al 2002, Spraul & Koenning 1994). Pes planovalgus is twice as common as varus heel alignment (pes cavus foot type) in these children (Mavidrou et al 1991).

Synovitis, effusion, erosive changes and deformity at affected MTP joints are observed in about one-fifth of JIA children and hallux valgus is common (Ferrari 1998). Deformities such as splaying of the forefoot; hammer, claw, and mallet toe deformity and MTP joint subluxation can rapidly develop. Leg length discrepancy, deformity and proximal joint malalignment resulting from growth disturbances can also impact on foot structure and function. Other problems such as Achilles tendinopathy, retrocalcaneal bursitis, tenosynovitis and plantar fasciitis occur in association with specific disease sub-types.

Disabling foot pain in JIA is associated with abnormalities in gait, either as a direct consequence of joint damage or as compensation to underlying impairments (Brostrom et al 2002, Hendry et al 2008, Witemeyer et al 1981). Typically these include reduced walking speed, increased double-limb support time, and step asymmetry. Gait can also be cautious and guarded with reduced heel-strike and push-off force (Brostrom et al 2002).

The commonest sites for osteoarthritis in the foot are the 1^st MTP joint (hallux rigidus), the ankle joint and the tarsometatarsal joints. Hallux rigidus is found in approximately 5% of adults above the age of 50 (Shereff & Baumhauer 1998) and is associated with trauma, metabolic and congenital disorders. The condition is often bilateral and affects more women than men. Patients may complain that the joint is stiff and painful and made worse by walking. Examination reveals a dorsal exostosis which is palpable and tender along the MTP joint line. Dorsiflexion motion is limited and painful. Radiographs reveal loss of joint space, dorsal osteophytes, subchondral bone sclerosis and cysts.

Primary osteoarthritis of the ankle joint occurs in less than 10% of all cases and over 70% are post-traumatic (Saltzman et al 2005, Valderrabano et al 2008). The lower rate of primary disease in comparison to the hip and knee is attributed to anatomic, biomechanical, and cartilage properties which protect the joint from degenerative changes (Huch et al 1997). Trauma is usually associated with malleolar fractures and ankle ligament lesions. The ankle is stiff and painful with mild-moderate effusion. Pain can be elicited on specific movements such as dorsiflexion/inversion and crepitus can be felt. Range of motion will be limited, the joint unstable and gait adapted to achieve relief. Bony enlargement, malalignment and/or deformity, can progressively develop (Fig. 13.3). Malalignment is distributed in favour of varus across all etiologies (55% varus, 37% neutral, 8% valgus) (Valderrabano et al 2008). Joint space narrowing, osteophtye formation, subchondral bone sclerosis, and cyst formation are typical radiographic features as well as varus malalignment, anterior protrusion of the talus and flattening of the tibial plafond (articular surface of the distal end of the tibia).

Figure 13.3 Malalignment and deformity of the ankle and subtalar joint in a patient with secondary, post-traumatic osteoarthritis.

Foot involvement is prevalent but often overlooked in the two most common connective tissue diseases; scleroderma and systemic lupus erythematosus (SLE). The feet are involved less frequently and later than the hands in scleroderma but nevertheless 90% prevalence has been reported (La Montagna et al 2002). Radiological changes in the joints in these patients include juxtaarticular demineralisation, distal phalange resorption, joint space narrowing, and extraarticular calcification. Radiological foot abnormalities have been reported in 26% of patients (Allali et al 2007). Approximately 90% of patients suffer from Raynaud’s syndrome which can lead to pain in the feet and digital ulceration, scarring and in some cases gangrene and amputation (La Montagna et al 2002, Sari-Kouzel et al 2001).

Localised thickening and tightening of the skin of the toes (sclerodactyly) and flexion contractures have been reported in 6% of cases (La Montagna et al 2002) and are associated with atrophy of the underlying soft tissues. Subcutaneous calcinosis occurs infrequently (6%) but can be extremely painful and disabling if it occurs on a weight bearing area of the foot. Whilst problems in the feet occur less frequently than those in the hand they can be a major source of morbidity and disability in patients with scleroderma.

Non-erosive arthritic manifestations (Jaccoud’s type arthropathy) involving the foot and ankle have been reported in patients with SLE. Common foot deformities found in these patients are hallux valgus, subluxation and fibular deviation of the MTP joints, and widening of the forefoot (Mizutani & Quismorio 1984, Reilly et al 1990). Erosive changes are rare in this group; however, hook like erosions caused by pressure erosion beneath the distorted joint capsules in the deformed joints may appear and have been reported at the metatarsal heads. Accelerated atheroma is a well recognised complication of SLE and abnormal ankle brachial pressure indices have been reported in almost 40% of patients (Theodoridou et al 2003). However, it rarely leads to critical peripheral ischaemia and gangrene is a relatively uncommon finding (Jeffrey et al 2008). Raynaud’s syndrome occurs in approximately 30% of cases (Bhatt et al 2007).

Sudden onset of pain, swelling, erythema and limited movement in the foot or ankle is characteristic of acute gout. The 1st MTP joint is most commonly involved, although acute gouty arthritis can involve the dorsum of the foot or ankle. Diagnosis of gout is established when monosodium urate (MSU) crystals are found in joint aspirate. Tophi are chalky white deposits of MSU that are large enough to be seen on radiographs and may occur at virtually any site but commonly occur in the joints of the hand and foot (Harris et al 1999). The rate of tophi formation correlates with duration and severity of hyperuricaemia (Gutman 1973). Intra-articular tophi are associated with the formation of bone erosions. However in contrast to RA, these are ill defined with overhanging edges and are not associated with osteopenia (Dalbeth et al 2007). Compared with RA, joint space narrowing occurs late in the disease or joint space widening may also occur in advanced disease (Dalbeth et al 2007). Moreover there is a strong relationship between bone erosion and the presence of intraosseous tophus. This suggests that tophus infiltration into bone as the dominant mechanism for development of bone erosion and joint damage in gout (Dalbeth et al 2008).

Pseudogout is much less common than gout and usually presents with a less severe clinical picture. It is characterised by deposition of calcium pyrophosphate dehydrate (CPPD) crystals in the joint or periarticular tissues which produces an acute inflammatory synovitis. Whilst the disorder is more common in the knee, hip, shoulder and wrist, it can also affect the 1st MTP joint and ankle.

Hypermobility (excessive mobility) can occur at a single joint or can be widespread throughout the body. There are several conditions associated with hypermobility, including Ehlers-Danlos disease, Marfan syndrome, osteogenesis imperfecta and benign joint hypermobility syndrome (BJHMS) which is the most common and will be the focus of this section. BJHMS has been defined as generalised joint laxity and hyperextensibility of the skin in the absence of any systemic disease. The pattern and course of musculoskeletal problems can vary considerably in patients with BJHMS from intermittent problems in a single joint to persistent widespread involvement of joints and soft tissues. A high proportion of patients with BJHMS have intermittent joint and soft tissue pain, joint effusions, dislocations, and they also have a tendency to bruise and scar easily.

Patients with BJHMS have poorer proprioceptive feedback and muscle strength, although this can be improved with proprioceptive exercises (Hall et al 1995, Sahin et al 2008a, Sahin et al 2008b). The proprioceptive system plays a critical role in maintenance of joint stability, including body position and movement of joints. Therefore deficits in proprioceptive function can make joints and soft tissues more vulnerable to minor traumas and may allow acceleration of degenerative joint conditions (Hall et al 1995). Hypermobility at the ankle and foot has been reported in a high proportion of patients. In the foot it is common for patients with BJHMS to report ankle instability and recurrent ankle inversion sprains (Finsterbush et al 1982). Other common features include joint instability, pes planovalgus deformity, subluxation of the MTP joints and hallux valgus (Fig. 13.4). In a review of a 100 consecutive patients, the most frequent complaint (48% of cases) was pain in the feet and calf associated with pes planovalgus deformity. Both general and local hypermobility at the 1st MTP joint have been linked with hallux valgus deformity (Carl et al 1988, Myerson & Badekas 2000).

Figure 13.4 Plantar pressure map showing high focal stresses at the MTP joints and weight bearing in the medial arch associated with pes planovalgus.