Joints are the point where two bones meet. They make your skeleton moveable -- you would not be able to bend your arm, walk or jump if you did not have joints. However, joints can't move without help, your muscles change the angle of joints when they contract or hold them still when they don't need to move. Three primary joints are used during a lunge, while many other joints play a supporting role.
Hip Joint
The hip joint is the primary joint used in a lunge. Your hip joint is formed by the meeting of your femur, the large bone of your thigh, and your pelvis. It is a ball and socket joint that allows for movement in all planes of motion. The hip joint moves through hip flexion and extension during a lunge, meaning that your femur comes closer to your body and then moves farther away again.
Knee Joint
Your knee joint is formed where your femur and tibia meet. The tibia is one of two bones of your lower leg and forms the bony part of your shin. The knee joint can only move in one plane of motion, unlike the hip. It bends and straightens during a lunge, allowing you to lower your center of gravity toward the floor.
Ankle Joint
The joint commonly referred to as the ankle is actually two joints -- the subtalar and talocrural joints. The subtalar joint allows for side to side movement, while the talocrural joints allows the ankle to bend and extend. The talocrural joint is the primary ankle joint used in a lunge and it dorsiflexes and plantar flexes. The subtalar joint may also move if your movement mechanics are poor, causing you to roll to the inside or outside of your foot.
Secondary Joints
Other joints might move during a lunge as well, although not to the extent that the hip, knee and ankle do. The joints between your vertebrae can move slightly during the lunge, depending on your posture and movement mechanics. Lunging with handheld weights like dumbbells, kettlebells and barbells places demands on your wrist, elbow and shoulder girdle joints.
Force Distribution
The torque placed on each joint varies depending on your exercise technique. Performing a lunge with your weight over your instep and your body upright decreases load around your knee joint, according to the Cybex Institute for Exercise Science. Performing a lunge with your weight over the ball of your foot and your body tipped forward increases the load around both the hip and knee joints.
References
- "Essentials of Strength and Conditioning"; Thomas R. Baechle, et al.; 2008
- Cybex Institute for Exercise Science: Biomechanical Analysis of the Lunge
- Sports Injury Clinic: Anatomy of the Ankle
