Sports Medicine and Exercise Information  

Dr. Allan Mishra | Knee Pain Diagnosis



(ACL Injury)

 Definition Partial or complete rupture of the Anterior Cruciate Ligament

Model and X-ray of a Normal Knee
Details Located in the center of the knee, the ACL is a strong band of tissue that prevents the shin bone (tibia) from extending excessively beyond the thigh bone (femur). ACL injuries are common and usually sports-related—especially associated with basketball, football and skiing.

The four primary stabilizers of the knee are the ACL, the PCL (Posterior Cruciate Ligament), the MCL (Medial Collateral Ligament) and the LCL (Lateral Collateral Ligament). These ligaments function in concert with the muscles and cartilage of the knee to help control motion. Proprioceptive (nerve) fibers in these ligaments and the capsule of the knee joint augment this control via reflex feedback

Arthroscopic Picture of Normal and Torn ACL
Causes An ACL injury may result from a violent, twisting motion (deceleration, valgus, rotation) of the knee, which can occur when an athlete plants his or her foot and suddenly changes direction. The ACL can also tear if the knee is 'hyperextended' (bent backwards).

Almost any sport that involves jumping, cutting or twisting has an inherent risk of an ACL rupture. Basketball, skiing, soccer and football are among the most common sports associated with this injury.
Diagnosis Patients with ACL tears usually describe a twisting or hyperextension of the knee. The patient may also feel a "popping" in the knee that is associated with immediate swelling. Typically, there is a significant effusion (excess fluid inside the knee) when the patient is first evaluated. A complete examination of the knee should be done to rule out associated injuries such as a fracture or a meniscus tear. The Lachman test is the best way to assess a knee for an acute ACL rupture. Range of motion should also be documented. Usually, the patient has difficulty fully straightening the knee immediately after the injury. This may be due to swelling or entrapment of the ACL stump in the intracondylar notch. Occasionally, a displaced bucket handle tear of the meniscus or a sprain of the medial collateral may present in conjunction with an ACL tear and lead to frank locking of the knee.

Lachman test

Meniscus tears

MRI of Normal and Torn ACL
Treatment ACL tears must be treated on a individual patient basis. Some patients with limited physical goals do very well with nonoperative treatment. Most patients, however, that wish to participate in cutting and twisting type sports should strongly consider ACL reconstruction to prevent further damage to the knee.

Nonoperative: Nonoperative treatment is indicated for patients with limited activity goals or with partial ACL tears. Initially, icing and an anti-inflammatory medication are recommended to control pain and swelling. Draining the knee may accelerate the recovery time. After the pain and swelling subside a program should be prescribed to increase knee range of motion and to strengthen the quadriceps and hamstrings muscles. Sport-specific drills in the later treatment stages help restore balance and coordination. Finally, using a brace when resuming sports-related activities may be helpful.

Operative: Operative treatment is indicated for patients who have giving way of the knee during activities of daily living or for patients who wish to return to cutting and twisting type sports. The combination of less invasive surgical techniques and more aggressive rehabilitation have made ACL reconstruction much better in the last few years. Many methods exists for reconstructing the ligament and are highly dependent upon the surgeon's training and experience.

The three most common ways to reconstruct the ligament are with a bone-patellar tendon-bone autograft, a hamstring autograft, or with some form of allograft tissue (patellar tendon and achilles tendon are the most popular). Screws or other devices are then used to secure the graft in position inside the knee. Allografts--which involve using tissue from cadavers--are a viable, and increasingly popular, graft option.

After the surgery, rehabilitation is begun within a few days. Restoring full knee range of motion is the initial goal. Strength, endurance and coordination drills are added as the patient improves. Typically, the patient may return to activities of daily living with a 1-3 weeks and progress to full sporting activity in 6 months depending upon the surgeon's preference and the patient's recovery. Many important choices must be made when having ACL surgery. A consultation with a surgeon of your choice should help clarify the options.

ACL Surgery: Incisions and Autograft Preparation


Maintaining excellent flexibility, strength and endurance of the quadriceps and hamstring muscles may prevent some ACL tears. It has been demonstrated that watching ski injury prevention videos reduces the incidence of ski related ACL tears. A review of the recent literature, however, reveals a dearth of articles related to ACL tear prevention. Clearly, more research is needed in this area.