General
principles of lower limb examination
Before you put the patient on the couch, ask them to walk up and down
and look at their gait. See if they are limping.
Types
of limp
The limp caused by any specific diagnosis is usually a complex mixture
of several pathological processes, which can be divided simply into the
following groups to produce an easily remembered (if ill-spelt) mnemonic:
• Long;
• Incoordinated;
• Muscle weakness;
• Pain;
• Stiff.
Long.
If one limb is short then the other is long in relation to it. The patient bobs
up and down when walking, when looked at from the front. However, the cadence
(rhythm) of the gait is normal. There is equal time spent on each limb.
Incoordinated.
The uncoordinated gait — walking has been described as controlled falling
(McNeil, Alexander). In patients with neuromuscular disorders the falling is
less controlled and so the patient’s limp is similar to a normal person who
has tripped or who is drunk. The arms are swung around to act as
counterbalances. The legs frequently scissor across each other and the gait has
no rhythm to it.
Muscle
weakness. Hip (Trendelenberg gait). The patient’s body sways
sideways to and fro when looked at from the front. The patient uses the trunk
muscles to lift the pelvis high enough to swing the leg through, as they cannot
lift the pelvis alone.
Knee.
Patients with weak quadriceps
(often seen after polio) use a trick manoeuvre to lock the knee as they take
weight on the leg. As they swing the leg forward, they flick the lower leg
forward so that the knee extends fully well before the heel strikes the ground.
They then hold the knee locked straight by keeping their hand in their pocket
and pushing back on the front of the thigh as the foot comes down to heel
strike. If they do not do this then the knee may buckle into flexion as they
start to take weight on the leg.
Ankle.
With a weak ankle the patient
lifts the foot very high in order to swing the leg through without catching
their toes. The foot also lands with a slap on the ground because there is no
control over it.
The
painful limp (antalgic gait). The patient spends less time on the painful limb
than the painless one. They also bob up and down when looked at from the front,
dropping down as they take weight on the bad limb, and rising back up again as
they take weight on the good limb. This gait can be confused with the ‘long’
leg gait, but there is a major difference. The cadence is abnormal. The gait
is dot—dash—dot—dash because so much less time is spent on the painful
limb than on the painless one.
The
stiff limp. Hip. The patient tends to sway forwards and
backwards when looked at from the side. They also hoist the pelvis up as they
bring the hip through to stop it dragging on the ground.
Knee.
Patients with a stiff knee often
swing the leg out to the side as they walk. This is because you need to be able
to lift the knee to avoid catching your toe on the ground as you bring the leg
forward for the next stride.
Ankle.
Patients with a stiff ankle walk
with a foot that rocks forward from heel to toe in a very pronounced way.