Motor System
Legs
BACKGROUND
Upper motor neurone or pyramidal weakness predominantly affects hip flexion, knee flexion and foot dorsiflexion.
Simplified root distribution in the legs is shown in Table 18.1
Table 18.1
| Nerve roots | Movement | Reflex |
| L1, L2 | Hip flexion | No reflex |
| L3, L4 | Knee extension | Knee reflex |
| L5 | Dorsiflexion of foot, inversion and eversion of ankle, extension of great toe | No reflex |
| S1 | Hip extension, knee flexion, plantarflexion | Ankle reflex |
Femoral nerve supplies knee extension.
Sciatic nerve supplies knee flexion. Its branches are:
WHAT TO DO
Look at the legs for wasting and fasciculation.
Note especially the quadriceps, the anterior compartment of the shin, the extensor digitorum and brevis, and the peroneal muscles.
Look for the position and for contractures, especially at the ankle; look at the shape of the foot, a high arch or pes cavus.
Pes cavus is demonstrated by holding a hard, flat surface against the sole of the foot; a gap can be seen between the foot and the surface.
Power testing screening
Compare the left with the right.
Hip flexion
Ask the patient to lift his knee towards his chest. When the knee is at 90 degrees, ask him to pull it up as hard as he can; put your hand against his knee and try to overcome this (Fig. 18.1).
Figure 18.1 Testing hip flexion
Hip extension
The patient is lying flat with his legs straight. Put your hand under his heel and ask him to push down to press your hand (Fig. 18.2).
Figure 18.2 Testing hip extension
Knee extension
Ask the patient to bend his knee. When it is flexed at 90 degrees, support the knee with one hand and place the other hand at his ankle and ask him to straighten his leg (Fig. 18.3).
Figure 18.3 Testing knee extension
Knee flexion
Ask the patient to bend his knee and bring his heel towards his bottom. When the knee is at 90 degrees, try to straighten the leg while holding the knee. Watch the hamstring muscles (Fig. 18.4).
Figure 18.4 Testing knee flexion
Foot dorsiflexion
Ask the patient to cock his ankle back and bring his toes towards his head. When the ankle is past 90 degrees, try to overcome this movement. Watch the anterior compartment of the leg (Fig. 18.5).
Figure 18.5 Testing dorsiflexion of the foot
Plantar flexion of the foot
Ask the patient to point his toes with his leg straight. Try to overcome this (Fig. 18.6).
Figure 18.6 Testing plantar flexion of the foot
Big toe extension
Ask the patient to pull his big toe up towards his face. Try to push the distal phalanx of his big toe down (Fig. 18.7).
Figure 18.7 Testing big toe extension
Extension of the toes
Ask the patient to bring all his toes towards his head. Press against the proximal part of his toes; watch the muscle (Fig. 18.8).
Figure 18.8 Testing extension of the toes
Additional tests
Hip abductors
Fix one ankle; ask the patient to push the other leg out at the side and resist this movement by holding the other ankle (Fig. 18.9).
Figure 18.9 Testing strength of hip abductors
Hip adductors
Ask the patient to keep his ankles together. Fix one ankle and try to pull the other ankle out (Fig. 18.10).
Figure 18.10 Testing strength of right hip adductors
Foot inversion
With the ankle at 90 degrees, ask the patient to turn his foot inwards. This frequently requires demonstration (Fig. 18.11).
Figure 18.11 Testing inversion of the foot
Foot eversion
Ask the patient to turn his foot out to the side. Then try to bring the foot to the midline (Fig. 18.12).
Figure 18.12 Testing eversion of the foot
