Joint Movement

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Proper joint movement is crucial for runners to improve performance, prevent injury, and enhance long-term health by allowing for a full range of motion, efficient biomechanics, and better stability. Key benefits include optimizing stride and form, reducing the risk of strains and overuse injuries, and improving overall efficiency and longevity as a runner.  

Adequate mobility allows joints to move through their full range of motion, leading to a more efficient and coordinated running stride, which can result in faster times and less energy expenditure.

Maintaining joint health through movement helps preserve long-term physical well-being. It's increasingly important as you age to prevent stiffness and maintain an active lifestyle. 

 The foot acts as a flexible adapter during initial contact and a rigid lever during push-off. Its motion is complex, involving multiple joints (subtalar, midfoot, metatarsophalangeal) and movements (pronation, supination, dorsiflexion, plantarflexion). 

• Stance Phase:
  • Initial Contact: The foot often lands in a slightly dorsiflexed and supinated position, though this varies by strike pattern (rearfoot, midfoot, forefoot).
  • Loading Response/Midstance: The ankle rapidly plantarflexes immediately after contact and the foot pronates (unlocks) to absorb shock and adapt to the ground surface. Pronation involves a combination of eversion, abduction, and dorsiflexion.
  • Propulsion (Push-off): The foot supinates (locks) to become a rigid lever, and the ankle moves into powerful plantarflexion to generate propulsive force. The metatarsophalangeal (MTP) joints undergo significant dorsiflexion (up to 70°) during toe-off.
• Swing Phase: The ankle dorsiflexes to ensure ground clearance as the leg swings forward.

Typical Foot with Ankle ROM during running:

• Dorsiflexion: Approximately 20° during the gait cycle (maximum during midstance/swing clearance).
• Plantarflexion: Up to 50° (maximum during push-off).
• Pronation/Supination (Subtalar joint): Ranges between approximately 15° of pronation and 45° of supination throughout the cycle.

The primary foot ligament involved in running is the plantar fascia, a thick band on the bottom of the foot that connects the heel to the toes. Lateral ankle ligaments are also crucial for stability, such as the anterior talofibular ligament, calcaneofibular ligament, and posterior talofibular ligament.

The plantar fascia supports the arch of the foot, absorbs shock, and plays a crucial role in walking, running.

• Arch support: It acts as a "tie-rod" to prevent the arch of the foot from collapsing under body weight.
• Shock absorption: It absorbs and redistributes the forces placed on the foot during impact from activities like walking, running, and jumping.
• Propulsion: It is essential for the "windlass mechanism," where dorsiflexion of the toes tightens the fascia, creating a rigid lever for an efficient push-off.
• Protection: It shields deeper structures of the foot, such as nerves and blood vessels, from pressure and injury.
• Stability: It helps stabilize the foot during the push-off phase of gait and provides overall stability, including through the reverse windlass mechanism for the transverse arch.

 The ankle primarily moves in plantarflexion and dorsiflexion.

• Stance Phase: At initial contact, the ankle is often slightly dorsiflexed and quickly moves into plantarflexion during midstance to absorb impact. It then rapidly transitions to significant plantarflexion during push-off to generate propulsive force.
• Swing Phase: The ankle moves through various degrees of plantarflexion and dorsiflexion to ensure ground clearance. It returns to a neutral position (0° of dorsiflexion/plantarflexion) by late swing in preparation for initial contact.
• Range of Motion: Interestingly, the total ankle ROM may not change significantly with running speed, unlike the hip and knee. Typical total ROM during running is approximately 45 degrees, encompassing peak dorsiflexion during midstance and peak plantarflexion at toe-off.

The knee primarily undergoes flexion and extension movements, along with some internal/external rotation and medial/lateral translation 

• Stance Phase: The knee is slightly flexed at initial contact and then rapidly increases flexion during early stance to absorb shock and lower the body's center of gravity. It begins to extend in midstance, reaching approximately 30° of flexion at toe-off.
• Swing Phase: After toe-off, the knee rapidly flexes to shorten the limb for ground clearance (up to 60° of flexion in early swing), then begins to extend in mid and late swing to prepare for the next contact.
• Range of Motion: The knee's ROM is substantial, often around 95 degrees for a run at a slow pace, and it generally increases with running speed, particularly the range of motion during ground contact.

 Range of motion by activity

• Walking: About 60 degrees of flexion.
• Stair climbing: Around 90 degrees of flexion.
• Sitting in a chair: Approximately 90 degrees of flexion.
• Squatting: Up to 115 degrees of flexion.
• Sprinting: Approximately 145 degrees of flexion.

Knee joint ligaments provide stability for running by controlling bone movement and preventing excessive side-to-side or front-to-back motion 

 Key ligaments in the knee for running

• Anterior Cruciate Ligament (ACL): Located in the center of the knee, it prevents the tibia from sliding too far forward relative to the femur.
• Posterior Cruciate Ligament (PCL): Also in the center, it prevents the tibia from sliding too far backward relative to the femur.
• Medial Collateral Ligament (MCL): Found on the inside of the knee, it provides stability by preventing the knee from bending inward excessively.
• Lateral Collateral Ligament (LCL): Located on the outside of the knee, it prevents the knee from bending outward too much. 
• Patellar ligament: Connects the kneecap to the shinbone and is a continuation of the quadriceps tendon.
• Anterolateral Ligament (ALL): This ligament is thought to help provide rotational stability to the knee during movement. 

 The hip experiences significant flexion and extension, as well as adduction/abduction and internal/external rotation. 

• Stance Phase: The hip is in flexion at initial contact and moves toward extension through the stance phase, reaching approximately 10-20° of hyperextension just before toe-off.
• Swing Phase: Following toe-off, the hip rapidly flexes, reaching around 30° of flexion by mid-swing, propelling the leg forward. At faster speeds, the hip requires more extension in early swing and more flexion in middle/late swing.
• Range of Motion: The hip has a large ROM during running, estimated around 40 degrees at a slow pace. This ROM has been found to increase with running-induced fatigue and tends to be greater in novice runners compared to experienced ones. Female runners also typically exhibit greater hip flexion angles and ROM compared to male runners.

Individual variation: This range is influenced by several factors:

• Sex: Some studies show females have a slightly higher average range (approx. 20.5 degrees) than males (approx. 18.2 degrees).
• Age: Range of motion tends to decrease with age.
• Physical activity: More active individuals generally have a greater range of motion. 

  The main ligaments of the hip joint are the iliofemoral, pubofemoral, and ischiofemoral ligaments, which form a strong, Y-shaped structure that wraps around the joint to provide stability. Other involved ligaments include the ligamentum teres, which connects the head of the femur to the acetabulum and provides blood flow, and the zona orbicularis, a circular ligament that reinforces the joint capsule. The acetabular labrum, a ring of cartilage, also contributes to stability by deepening the socket. 

Extra-articular ligaments

• Iliofemoral ligament: A strong, Y-shaped ligament on the front of the hip that prevents hyperextension and external rotation.
• Pubofemoral ligament: A triangular ligament on the lower front of the hip that limits abduction and extension.
• Ischiofemoral ligament: A posterior ligament that limits internal rotation and extension. 

 Intra-articular ligaments

• Ligamentum teres: A small ligament located inside the joint capsule that connects the femoral head to the acetabulum. It was once thought to be the main source of blood flow to the femoral head, but this function is debated in adults.
• Zona orbicularis: A circular band of fibers that encircles the femoral neck like a collar, reinforcing the joint capsule.