Table 1 Details of home-based exercises

Isometric contractions of the quadriceps

1. Sitting or lying down, legs relaxing;

2. Tight the thigh muscles on one side with maximum strength, keep it for 5 s, and relax for 2 s. Repeat 10 times for 1 group and practice 10 groups in succession;

3. Relax this leg and repeat the above action on the other side;

4. Exercise alternately 3 to 5 times with both legs.

Supine straight-leg lifts

1. Lie on the back, stretch knees;

2. One leg is flexed to support the bed surface, the other leg is raised to the heel, about 20 cm away from the bed, held for 5seconds, put down for 5 s, repeat 10 times;

3. Relax this leg and repeat the above action on the other side;

4. Exercise alternately 3 to 5 times with both legs.

Leg lifts in the prone position

1. Lie face down, stretch knees;

2. Lift one leg back to the toe, about 20 cm away from the bed, held for 5 s, put down for 5 s, repeat 10 times;

3. Relax this leg and repeat the above action on the other side;

4. Exercise alternately 3 to 5 times with both legs.

Passive knee flexion

1. Sit on the bed;

2. Hold your hands on one side of the ankle, slowly and forcefully hold the leg to the chest to maximize knee flexion, keep60 s;

3. Relax this leg and repeat the above action on the other side;

4. Exercise alternately 2 to 3 times with both legs.

Passive knee extension

1. Sit on the bed;

2. Put one side of the foot pad 8~10 cm high;

3. Apply light weight to the raised knee joint or apply proper pressure by hand for 60 s;

4. Relax this leg and repeat the above action on the other side;

5. Exercise alternately 2 to 3 times with both legs.

Resistance knee extension

1. Sit on the chair or at the bed, tie a 1 kg sandbag to the ankle, keep the upper body straight;

2. Do not move the thighs, lift your calves until the knees are fully extended, hold for 5 s, rest your legs for 5seconds, repeat 10 times;

3. Relax this leg and repeat the above action on the other side;

4. Exercise alternately 2 to 3 times with both legs.

Resistance knee flexion

1. Standing up, tie a 1 kg weight sandbag to the ankle joint, and support the upper edge of the chair;

2. Stand on one leg and pull the calf back to the other leg, flexing the knee as much as possible while keeping the thigh perpendicular to the ground. Hold for 5 s, put your legs down for 5 s, repeat 10 times

3. Relax this leg and repeat the above action on the other side;

4. Exercise alternately 2 to 3 times with both legs.

Shifting the center of gravity (left and right)

1. Stand up and support a table with a height of 70~80 cm and open the feet;

2. Keep your knees upright, slowly move the center of gravity to the left, and gradually lower your right heel;

3. Keep your knees upright, slowly move the center of gravity to the right, and gradually lower your left heel;

4. Repeat the above action for 3 min.

Shifting the center of gravity (forwards and backwards)

1. Stand up and support a table with a height of 70~80 cm and take one step forward on one side;

2. Keep the knees upright, slowly move the center of gravity forward, and the heel of the hind foot gradually leaves the ground;

3. Keep the knees upright, slowly move the center of gravity backwards, and the forefoot gradually leaves the ground;

4. Repeat the above action for 3 min.