• Make sure that you have adequate exposure on both sides so that the normal can be compared with the abnormal. Use the system ‘look, feel, move’ (see Chapters 3, 21) and always check distal neurovascular status.
  
• Watch the patient walk, looking for any signs of a limp, which could be caused by pain (antalgic), weakness (Trendelenburg limp) or deformity (short). A painful hip is held flexed, adducted and internally rotated so the leg appears short.

It can be difficult to tell whether pain in the upper leg is coming from the hip, the knee or even the back. In the ‘ pastry roll’ test , let the patient relax then roll the leg in and out with the flat of one hand on their thigh and the other on the shin as if you were rolling pastry. If the hip is pain-free the foot will flop to and fro. If there is pain arising from the hip then the patient will resist this rolling.

When checking range of movement, lie the patient on their back and then ask them to curl into a ball. Compare the flexion of the hip with the other normal side. Then, get them to use their hands to hold the normal hip in that flexed position (this fixes the position of the pelvis) and gently allow the affected hip to extend as far as is comfortable. If there is fixed flexion deformity the leg will not be able to extend out onto the couch (modified Thomas’ test). When checking the range of rotation, just flex the hip enough to allow you to bend the knee to a right angle. Then use the tibia as a dial indicating the amount of rotation that can be achieved.

Check for wasting of the vastus medialis, bulging just above and inside the knee cap when the patient forces their knee back into hyperextension. It is an early and sensitive sign of knee pathology.

An effusion in the knee is best seen by the loss of the dimple on the inside of the knee cap when compared with the other side. The commonest bony deformity is bowing of the knees (varus) caused by osteoarthritis of the medial compartment.

Range of movement

Range of movement can be compared by first lifting both heels off the bed to check for loss of extension, then seeing how far up to the buttock the heel can be drawn when the patient is lying on a couch.

The quadriceps lag test

To test the power of the extensor mechanism of the knee the patient should be asked to lift their leg straight until the heel is 20 cm off the bed. They should then be asked to bend the knee until the heel touches the couch then straighten it again. If they cannot straighten it again they have a quadriceps lag. If this is present then the knee must be splinted and urgent physiotherapy arranged as otherwise they are liable to trip and suffer a secondary injury.

Stability

The collateral ligaments are checked by stressing the knee first into varus (inwards), then valgus (outwards), with the knee very slightly bent. The knee needs to be very slightly flexed when performing this test as otherwise the tight posterior structures may mask collateral tenderness (a partial tear) or laxity (a complete tear).

Cruciate ligament instability is revealed by finding that the tibia is loose on the femur when pulled forward. Sit on the end of the couch, with the patient’s feet tucked side by side under your thigh to hold them still. First look from the side to see if one tibia has sunk back on the femur (ruptured posterior cruciate). Then with both hands gripping the top of the tibia, gently pull it forward on the femur.

• If the distance that it will draw forward is much more than the other side, then a cruciate ligament is probably ruptured.
  
• If the tibia moves from a sagged back position forward to a normal position (compared with the other side) then it is the posterior cruciate ligament that is ruptured.
  
• If the tibia floats forward from a normal to an abnormal position, then the anterior cruciate has failed.

Pushing the patella laterally as you bend the knee will be resisted by patients who have had a previous dislocation of the knee cap (patella apprehension sign).

Range of movement

Range of movement in the ankle, the subtalar joint and the forefoot can all be checked by holding the heel in one hand and the forefoot in the other.

• Rocking the hands up and down checks plantar and dorsiflexion at the ankle joint.
  
• Tipping both hands in (inversion) and out (eversion) tests mobility in the subtalar joint.
  
• Twisting the hand holding the forefoot in (pronation) and out (supination), while holding the hindfoot still, checks movement in the small joints of the forefoot.

Check the skin all over the forefoot for bunions and corns, and on the sole of the foot for thickened pads over the metatarsal heads.

Pathological flat feet are only reliably visible when the patient stands on their toes. A physiological flat foot (part of the normal spectrum) will form a normal arch on tip-toe. In pathological flat foot no arch forms, suggesting that there may be an abnormality in the bones of the foot.