Your leg has three main bones: The femur, a long and sturdy thigh bone, that's the biggest bone in your body. Below the knee is the tibia, the second-largest leg bone, and, below that, the fibula. If you break any of bone, it will take anywhere from a few weeks to a few months for it to heal—and then you can start the physical process of regaining strength.
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The First Month
The sooner you start putting some weight on the leg, the better. Dedicate the first month after initial treatment to rest and light exercises, such as simple leg raises to keep the hip muscles from weakening, as well as straight leg raises while lying on your back, side or stomach.
Whether or not you can do knee-bending exercises depends on the type of break and whether you had surgery. Sometimes you'll have a full-leg cast, and your knee will be immobile. If it isn't, you can do leg extensions while sitting in a chair — simply bend your leg, straighten it back out and repeat.
After a month, you can start doing exercises for the leg and other parts of your body. With the help of a physical therapist, you'll also start walking with more weight on the leg. Sometimes you can start swimming, as long you have no open wounds from surgery and the leg isn't in a cast.
For your lower body, do machine exercises like leg extensions, leg curls and leg presses on the non-injured leg. Try to avoid free weight exercises initially because the weight is less predictable. Continue doing straight leg raises on the injured leg.
With the help of your physical therapist, you'll slowly start bending the knee of the broken leg. You'll try to get it to bend to at least 90 degrees without any resistance. Then you can add weighted exercises like leg extensions and leg curls to build up the thigh muscles.
Eventually, you can add leg presses to work your glutes, quads, and hamstrings. After that, within two to three months after surgery or injury, you should be ready to start bodyweight exercises.
At first, step-ups on a 6-inch high box or even lower will get you used to putting some weight on the leg. Squats with very shortened range of motion will also help. After three to four months, you'll slowly gain more range of motion in your squats.
Month Four and Beyond
After a three to four months of recovery, you should be able to train as you normally did before your surgery. Work on leg exercises like squats, lunges and step-ups to continue improving your leg strength.
Read More: How to Exercise With a Broken Tibia & Fibula