UNHAPPY TRIAD OF O'DONAHUEBy: Guadalupe Guzmán

CLINICAL CASE

A 20-year-old man walks into a physical therapy clinic using bilateral crutches with a brace on his right knee. The surgeon's referral states that the patient has had a tibial collateral ligament (TCL) repair, anterior cruciate ligament (ACL) repair, and medial meniscus debridement. The surgeon includes a rehabilitation protocol based on the surgeon's preference.

MECHANISM OF THE INJURY

The patient injured his knee after catching the inner edge of his ski forcing him to fall. He described hearing a snap and experienced immediate pain and swelling. He immediately contacted a doctor who, after viewing the patient's magnetic resonance image (MRI), diagnosed the patient with the unhappy triad of O'Donahue.

ANATOMY

WHAT IS THE UNHAPPY TRIAD OF O'DONAHUE?

The unhappy triad of O'Donahue consists of:

- a tear in the ACL, TCL, and medial meniscus.

It’s typically caused by excessive tibial external rotation on a stationary foot causing a valgus stress on the knee.

WHAT ARE THE CLINICAL TESTS TO DETERMINE THE PRESENCE OF A TEAR?

ACL integrity Anterior Lachman's test

The patient is supine during the anterior Lachman's test. The physical therapist places one hand around the distal femur, the other hand around the proximal tibia, and holds the knee in about 20° of flexion, maintaining stability with the hand on the distal femur. The physical therapist then applies a quick anterior force on the proximal tibia. If the physical therapist does not feel a firm endpoint, the test is positive for an ACL tear.

ACL INTEGRITY

Anterior drawer test The patient is supine during the anterior drawer test and the knee is placed at a 90° angle with the foot flat on the table. The physical therapist sits on the foot to stabilize it, then wraps both hands around the proximal tibial with the thumbs on the femoral condyles and the fingers on the hamstring tendons. It is important to make sure that the hamstrings are relaxed during this test. The physical therapist then applies an anterior force to the tibia and should feel a firm endpoint. If the tibia moves anteriorly without a firm endpoint, the test is positive for an ACL tear.

ACL INTEGRITY

Pivot shift test The patient is supine during the pivot shift test, and the physical therapist places one hand behind the proximal tibia and the other holding the foot. The physical therapist then places an anterior and valgus force on the tibia as the patient's knee and hip are passively flexed. If the ACL is not intact, a 'clunk' will be felt at around 30-40° of knee flexion as the iliotibial band pulls the tibia into place.

TCL INTEGRITY

Valgus stress test The patient is supine during the valgus stress test, and the physical therapist holds the knee in approximately 20-30° of flexion with one hand on the medial mid tibia and another hand on the lateral aspect of the knee joint. The physical therapist then places a valgus stress on the knee and should feel a firm endpoint. If a firm endpoint is not felt, the test is positive for a TCL tear. In all tests, the physical therapist should be comparing the test to the uninvolved side. If there is a difference in joint excursion, there may be a tear.

MEDIAL MENISCUS TEAR

McMurray's test The patient is supine during McMurray's test with the knee fully flexed. The physical therapist places one hand beneath the plantar aspect of the patient's foot and the other at the distal femur and compresses the knee joint and rotates the tibia into internal and external rotation as the knee is extended to about 90°. The test is positive for a meniscal tear if pain is increased or if there is palpable grinding or catching.

Apley's compression test The patient is prone during Apley's compression test, and the physical therapist holds the knee in 90° of flexion, using one hand on the plantar surface of the foot to add a downward compression force on the knee joint. The tibia is then passively rotated, and the knee can be further flexed or extended to determine the integrity of the menisci. The test is positive for a meniscal tear if pain is increased or any catching or grinding is felt

TREATMENT

Typically, the TCL is surgically repaired and the ACL is reconstructed using either a semitendinosus or patellar tendon autograft (from the patient) or a patellar tendon or a calcaneal tendon allograft (from a cadaver).

The patellar tendon autograft is most commonly used because it is a stronger graft, but could produce patellar-femoral pain, quadriceps weakness, or patellar tendinitis. The semitendinosus autograft is not as strong and may have an extended protected weightbearing time, but causes fewer problems with the patellar-femoral joint.

An allograft is typically used for more active patients who are older than 30 years because their tendons may be weaker. Infection or rejection of the graft is possible. Finally, the medial meniscus will either be repaired or debrided based on the location of the tear.

PHYSICAL THERAPY

The physical therapy treatment following this type of surgery varies based on the surgeon's chosen protocol as well as the type of surgery performed.

Initially, the treatment options will be limited depending on the weightbearing status and the amount of motion that is allowed by the surgeon. The physical therapist needs to gain as much joint motion and strength as possible and progress as permitted.

The treatment regarding the ACL repair initially begins with quadriceps sets, straight leg raises, mini squats, and leg extensions using a Thera band limited to 90-60° of flexion only. This is to limit the anterior translation of the tibia, which may place excess stress on the ACL. In an open chain (non-weightbearing) position, the tibia translates anteriorly as flexion becomes less than 60°. This anterior translation may cause more stress on the ACL.

As the surgeon allows more activity, strengthening can then progress to using the leg extension machine from 90-60° of flexion only, leg curls from 0-90° of flexion, and leg press from 0-45° of flexion. In a closed chain (weightbearing) position, the amount of anterior translation of the tibia increases as the knee is flexed more than 45°, which may place more stress on the ACL. Based on certain studies, anterior translation of the tibia can be decreased if these exercises are limited to the specified degrees. It is undetermined whether decreasing the anterior translation protects the ACL from excessive strain, but some protocols will limit motion in this way to be safe.

As the surgeon allows, treatment can progress to balance training and functional retraining based on the desired activity level of the patient.