Test the power in muscle groups—hip flexion (L1, L2—iliopsoas—straight leg raise); knee flexion (L5 to S2—hamstrings—the patient tries to bend the knee while the examiner applies force to the leg to hold the knee in extension); knee extension (L3, L4—quadriceps femoris—the patient attempts to keep the leg straight while the examiner applies a force to the leg to flex the knee joint); ankle plantarflexion (S1, S2—the patient pushes the foot down while the examiner applies a force to the plantar surface of the foot to dorsiflex the ankle joint); ankle dorsiflexion (L4, L5—the patient pulls the foot upward while the examiner applies a force to the dorsal aspect of the foot to plantarflex the ankle joint).
Examine knee and ankle reflexes—a tap with a tendon hammer on the patellar ligament (tendon) tests reflexes at the L3–L4 spinal levels, and tapping the calcaneal tendon tests reflexes at the S1–S2 spinal levels.
Assess status of general sensory input to lumbar and upper sacral spinal cord levels—test light touch, pin prick, and vibration sense at dermatomes in the lower limb.
In the clinic
Footdrop is an inability to dorsiflex the foot. Patients with footdrop have a characteristic “steppage” gait. As the patient walks, the knee of the affected limb is elevated to an abnormal height during the swing phase to prevent the foot from dragging. At the end of the swing phase, the foot “slaps” the ground. Also, the unaffected limb often acquires a characteristic tiptoe pattern of gait during the stance phase. A typical cause of footdrop is damage to the common fibular nerve, which may occur with fractures of the fibular neck. Other causes include disc protrusion compressing the L5 nerve root, disorders of the sciatic nerve and the lumbosacral plexus, and pathologies of the spinal cord and brain.
In the clinic
The common fibular nerve is susceptible to injury as it passes around the lateral aspect of the neck of the fibula. It can be injured as a result of a direct trauma (blow or laceration), secondary to knee injury (knee dislocation), or as a consequence of a proximal fibular fracture. Sometimes damage to the nerve can be iatrogenic, that is, damaged during arthroscopy or knee surgery.
Symptoms of common fibular nerve injury are often observed in bed-bound patients, particularly in those with decreased levels of consciousness, due to prolonged external pressure to the knee leading to nerve compression and neuropathy. Similarly, application of a tight cast or a brace to the leg can compress the nerve, producing symptoms of fibular muscle palsy.
Apart from a foot drop, other symptoms of common fibular nerve injury include loss of sensation over the lateral aspect of the leg and dorsum of the foot, and wasting of fibular and anterior tibial muscles.
In the clinic
Occasionally there is a superior projection of the distal aspect of the talus, which is beak-shaped (Fig. 6.101). It is often associated with the presence of a bony or fibrous joint between the talus and calcaneus.
In the clinic
Fracture of the talus
The talus is an unusual bone because it ossifies from a single primary ossification center, which initially appears in the neck. The posterior aspect of the talus appears to ossify last, normally after puberty. In up to 50% of people there is a small accessory ossicle (the os trigonum) posterior to the lateral tubercle of the posterior process. Articular cartilage covers approximately 60% of the talar surface and there are no direct tendon or muscle attachments to the bone.