How do I do straight leg raises without hurting my knee or back?

Step by step

• 1. Lie on your back on a firm bed or mat
• 2. Bend the non-working knee so that foot is flat; this protects your lower back
• 3. Do a quad set on the working leg first: tighten the thigh and press the back of the knee down
• 4. Keeping that tension, lift the straight leg to about the height of the other knee, over two seconds
• 5. Hold for two to three seconds at the top
• 6. Lower slowly over three seconds and relax fully on the bed
• 7. Start with eight to ten repetitions, two or three times a day

Signs you need to adjust

If the knee bends as the leg lifts, called an extensor lag, the quadriceps is not yet strong enough. Go back to quad sets for a few more days or lift only a few centimetres.

If your lower back arches or aches, check that the other knee is bent and gently draw your belly button in. If the front of the hip pinches, lift lower.

Progressing the exercise

• Increase to three sets of ten once one set is easy and the knee stays straight
• Add a light ankle weight, or a bag of rice in a sock, when your physiotherapist agrees
• Try the same lift lying on your side to work the hip, and lying face down for the buttock
• Move on to standing exercises such as sit-to-stands, which load the knee in a more everyday way

Safety notes

Straight leg raises put very little stress through the inside of the knee, which is why they are used so early. Even so, stop if you feel sharp pain in the knee, a pulling pain in the groin, or tingling in the leg. After surgery, follow any restrictions your surgeon has given; some repairs, for example of the tendons around the kneecap, need a modified programme.

If you still cannot lift a straight leg several weeks after an injury, or the leg suddenly becomes impossible to lift after a fall, see a knee specialist promptly, as this can point to a tendon problem.