Certainly! Strain injuries, also known as muscle strains, occur when the muscle or tendon is stretched beyond its limit or torn due to overuse, improper use, or sudden excessive force. These injuries can range from mild to severe and are often categorized by three grades:

• Mild strain: This involves overstretching or small tears in the muscle or tendon. It typically causes mild pain, minimal swelling, and doesn't significantly impact movement.
• Moderate strain: This grade involves more extensive damage to the muscle or tendon. It can result in significant pain, swelling, bruising, and difficulty moving the affected area. The muscle or tendon may partially tear but is not completely ruptured.
• Severe strain: This is a serious injury involving a complete tear or rupture of the muscle or tendon. It causes intense pain, significant swelling, bruising, and renders the affected area immobile. Surgery might be required in severe cases.

Common causes of strain injuries include:

• Overexertion: Engaging in physical activities without proper conditioning or warming up can strain muscles.
• Repetitive Movement: Performing the same motions repeatedly can strain the muscles involved.
• Poor Posture or Technique: Improper form during physical activities can strain muscles over time.
• Sudden Force: A sudden forceful movement or impact can cause strains.

Rehabilitation might also include gentle stretching and strengthening exercises once the initial acute phase has passed to promote healing and prevent re-injury. Severe strains might require medical attention, physical therapy, or even surgical intervention.