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The Unhappy Triad of O’Donoghue

Shehzad Surya, PT - Registered Physiotherapist


unhappy triad

The “unhappy triad” refers to a sprain injury that involves three structures of the knee. These structures are the medial collateral ligament, anterior cruciate ligament, and the medial meniscus. The unhappy triad is a severe injury, and it is named such because the athlete who suffers it typically becomes really unhappy. The severity of this injury typically leads to surgery to fully correct.


What Causes the Unhappy Triad? 

The mechanism for the unhappy triad injury occurs when a lateral force to the knee is received while the foot is fixed on the ground. This places an increased valgus, or abduction, and rotational stress on the knee that results in the overstretching of these three structures. When the ligaments in the knee fail, increased stress may be suddenly placed on the medial meniscus, causing injury or a tear there.


A good example of the unhappy triad occurring is during a tackle in football when the athlete is hit on the outside of his knee while in the standing position with the foot planted on the ground.


Physical Therapy After Experiencing the Unhappy Triad

If you have the unhappy triad, you may benefit from physical therapy. Your therapy should focus on regaining normal motion and function in your knee. Your physical therapist may use therapeutic modalities like ice, ultrasound, or electrical stimulation to help control your pain. Research into the use of modalities shows varied results; some studies show improvements with things like ultrasound or e-stim, while other shows no extra benefit from using these modalities.


A form of electrical stimulation called NMES may be used to help improve the way your quadriceps muscles contract after you suffer the unhappy triad. With any knee injury, the quads tend to shut down while healing is occurring, a condition known as quadriceps inhibition. This occurs due to pain and swelling in your knee joint. Getting your quads working properly again is of utmost importance, and your PT may use NMES to accomplish that task.


Typically, swelling around your knee may limit its range of motion (ROM) when you suffer the unhappy triad. Physical therapy knee ROM exercises may be performed to help restore normal mobility to your joint.


Since the unhappy triad involves the tearing of two ligaments, your knee will likely feel very unstable. Exercises to improve balance and proprioception may be incorporated into your physical therapy program.


Surgery is often performed to repair the ligaments and meniscus in your knee if you have the unhappy triad. After surgery, you will likely require physical therapy to help you restore normal mobility and strength in your knee. Your physical therapist can help you regain your functional mobility and can help you return to your previous level of function and activity.

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