REHABILITATION FOCUS

REHABILITATION OF SINUS TARSI SYNDROME

By Dylan Morrissey, MCSP

Sinus tarsi syndrome (STS) is a common, under-recognised and recalcitrant ankle problem arising either as a result of trauma to the ankle or due to repetitive loading in a biomechanically compromised lower limb.

Post-traumatic STS commonly persists after the associated injuries have healed eg. associated ligament sprain, cuboid subluxation or in conjunction with persistent osteochondral lesions. This renders the athlete unable to participate or to under-perform due to per- sistent pain and loss of function. It is a particular rehabilitation challenge due to the complex nature of the sub-talar joint (STJ) and its role in torque conversion of vertical forces during weight- bearing activity.

The potential knock-on effects of sub-talar joint pathology include dysfunction in the rest of the foot, at the knee and at the hip.

Anatomical and biomechanical considerations The sub talar joint, due to the obliquity of its axis, and the shape of the joint surfaces converts the vertical force exerted during weight bearing to a more horizontal force by means of a complex triplanar movement. This movement is produced as a result of the posterior articulations of the talus being concave while the ante- rior are convex.

The rules regarding the direction of accessory movements occur- ing in conjunction with physiological movements still apply, but as the joint surfaces oppose each other in terms of orientation a complex twisting movement occurs. Variations in the inclination of the sub talar axis will result in variations in amounts of supina- tion and pronation taking place during movement. The stability of the joint is primarily provided by the interosseous and cervical lig-

Anterior tibio- fibular ligament

Talus

Inter-osseous talocalcaneal

ligament Subtalar ligaments

Cervical ligament

Differential diagnosis of STS ● Ligament injury eg. ATFL ● Cuboid instability ● Stress fracture eg. calcaneus ● Osteoarthritis of the sinus tarsi joint ● Osteochondral lesion of the talar dome ● Somatic referred pain eg. lumbar spine ● Myofascial referral eg. from peroneii ● Inferior tibio-fibular joint disruption ● Adverse neural dynamics eg. sural nerve

Box 1

aments (Fig.1). These are short strong ligaments that are crucial to the stability of the joint and to the alignment of the foot and lower limb in general. The ligaments lie within the sinus tarsi, an enclosed space between the talus and calcaneus. This position appears to cause healing to be slow and makes direct soft tissue manual therapy very difficult.

Rehabilitation is further complicated by the lack of any direct talo-calacaneal muscles so stabilisation is achieved indirectly via the long shin-foot muscles acting in complex force couples.

Particular muscles of interest are the tibialis anterior, tibialis pos- terior, long flexors, triceps surae and peroneii. Some of the short foot muscles arising from the calcaneum may also have a role in stabilising the joint.

©1999 Primal Pictures Ltd Sinus tarsi tunnel

Figure 1: Antero-lateral view of the deep ligaments of the ankle 16 SportEX

Assessment Trauma The key to prompt resolution of traumatically induced sinus tarsi is early diagnosis. This allows management to include STS treat- ment while addressing other assessment findings. Clinical findings include: ● Pain over the antero-lateral aspect of the ankle, which may be diffuse and refer surprisingly far from the joint both proximally and distally. The symptoms may also include medial pain although this is unusual and usually relates to associated pathology or dys- function ● STJ laxity or stiffness with or without pain on stress testing: distinct entities which must be treated differently especially in terms of manual therapy ● Pain on palpation of the anterior opening of the sinus: this must be differentiated from ATFL, bifurcate ligament and inferior tibio-fibular ligament injury in particular ● Deep vague ache within the ankle ● An inability to cope with impact, particularly involving rota- tion or directional change ● Exclusion of other differential diagnoses (Box 1)