Unhappy Triad or Blown Knee or Terrible Triad

Unhappy Triad or Blown Knee or Terrible Triad is a medical condition involving acute injury to the knee. It is named so because it involves injury to three major structures of the knee which are:

  1. Anterior Cruciate Ligament.
  2. Medial Meniscus.
  3. Medial Collateral Ligament.

Unhappy Triad or Blown Knee or Terrible Triad

Unhappy Triad or Blown Knee or Terrible Triad involves partial or full tears of these 3 major structures. Terrible Triad and O'Donoghue Triad is also a name given to the Unhappy Triad. It also involves other skeletal elements such as patella, femur and tibia. Muscles are not directly involved in this type of injury, only the ligaments are involved, but strengthening the hip flexor and hip extensor muscles greatly helps in relieving this type of injury. The major ligaments of knee are the MCL, PCL, ACL and LCL. The medial and lateral collateral ligaments mainly support the varus and valgus forces. The anterior and posterior cruciate ligaments inhibit the anterior and posterior translation of the tibia on the femur.

Etiology of the Unhappy Triad or Blown Knee or Terrible Triad

Unhappy Triad or Blown Knee or Terrible Triad is a severe knee injury involving complete or partial tears of three major structures of the knee which are the ACL, medial meniscus, and MCL. This type of severe injury results after exorbitant force is applied to the knee. This type of extensive force usually occurs with contact sports rugby, soccer etc. It may also occur due to car accidents or other traumatic injuries to the knee. If the knee gets twisted while the foot is fixed to the ground, then also it results in the unhappy triad. Around 10% of the cases involve force to the opposite side of the knee resulting in torn lateral and posterolateral ligaments.

Symptoms of Unhappy Triad or Blown Knee or Terrible Triad

  • Traumatic injury causing severe knee pain.
  • Instant and acute swelling.
  • Audible pop or tear in the knee at the time of injury.
  • Difficulty in knee movements, especially during full range of motion.
  • Stiffness in the injured knee.
  • Pain upon knee movement.
  • Bruising commonly appears within a couple of days.
  • Uneven sensation of the knee or instability of the knee which feels as though the knee is "giving out."
  • Catching or locking of the affected knee.

Treatment for Unhappy Triad or Blown Knee or Terrible Triad

Conservative Treatment for Unhappy Triad or Blown Knee or Terrible Triad

  • Applying ice packs.
  • Resting the knee.
  • Keeping the knee elevated and supporting it.
  • Compression bandages are also beneficial.

Surgical Treatment for Unhappy Triad or Blown Knee or Terrible Triad

Studies like x-ray or magnetic resonance imaging is beneficial for confirmation of the diagnosis. If the injury is severe then surgery is recommended. Surgical options include ACL reconstruction with a graft which is commonly taken from the hamstrings or patellar tendon. The types of grafts which are done for repair of torn ACL in the Unhappy Triad are hamstring tendon autograft, quadriceps tendon autograft, and patellar tendon autograft. Treatment for torn meniscus is meniscectomy, repair of the tear of the meniscus, and transplantation of the meniscus. The MCL usually heals by itself. The leg should be immobilized with the help of a knee brace so it can heal faster. An extensive rehabilitation program should be undertaken by the patient in order to regain complete strength and motion of the knee. Certain factors should be taken into consideration before deciding on surgery such as the patient's activity level, patient's involvement in sports or labor intensive occupation, age is another important factor that should be considered before deciding on surgery as there can be complications in very young patients who are still growing. General health of the patient should also be considered and the patient's ability to withstand the surgery. Patient's support system should be strong as the patient requires help for his needs after surgery.

Written, Edited or Reviewed By:


Last Modified On: August 10, 2017

Pain Assist Inc.

Pramod Kerkar
  Note: Information provided is not a substitute for physician, hospital or any form of medical care. Examination and Investigation is necessary for correct diagnosis.

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