Orthopaedic Surgery, Sports Medicine and Rehabilitation

Common Knee Injuries

ACL Tear

History: This is usually a non-contact injury (70 percent of the time) and usually involves valgus, flexion, and external rotation. Often a "pop" is heard/felt, the patient is unable to continue to play, and has to be helped to the sideline. It is felt to be a serious injury with large effusion that worsens overnight. The patient walks for about a week with bent knee limp and feels relatively normal by three weeks. They may have additional "giving way" episodes before seeking help. This can also occur from contact injuries and is one of three common causes for acute knee effusion. Meniscal injuries also occur with ACL tears about 60 to 70 percent of the time (lateral is most common). Other ligament injuries occur 10 to 15 percent of the time (MCL is most common).

Findings: Lachmans, plus/minus anterior drawer, flexion rotation drawer and pivot shift. The patient may walk with a bent knee limp and effusion for at least the first week. He/she may have a lack of full hyperextension (note: if lack of full hyperextension is greater than 10 degrees, the patient may have a displaced medial bucket handle meniscus tear and an MRI may be warranted). There is joint line tenderness with acute ACL not diagnostic of meniscus tear.

Treatment: The patient should regain full range of motion. Primary repair of the injury is no longer indicated. Reconstruction is indicated (grafts include bone-patella tendon-bone, hamstrings, or various allografts) if performing high-risk activities (involving cutting type activity), or chronic giving way episodes occur. The key is to avoid "giving way" episodes, as they increase the risk of meniscus tears and meniscus tears increase the chance of arthritis.

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MCL Tear

History: The MCL tear is one of three common causes for acute knee effusion and is much less common than the other two causes (ACL tear and patella D/L). This often is a contact injury with pain on the medial aspect of the knee. It can be proximal or distal, depending on where the ligament is injured. Proximal injuries result in larger effusions, with more stiffness, but shorter healing times.

Findings: The patient has medial tenderness (proximal over medial epicondyle for proximal injury, or distal to joint for distal injury), likely effusion (effusion is larger for proximal MCL injury), and laxity with valgus stressing.

Treatment: The patient should regain full range of motion. Bracing/casting may be helpful in high-grade injuries.

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Meniscus Tear

History: Degenerative meniscus tears commonly occur in males more than 40 years old (MMT) or females more than 50 years old (LMT). Pain is usually in the middle medial aspect of the joint line (MMT) or lateral joint line (LMT), sometimes precipitated by a twisting injury, but can occur without injury. Often pain with squatting and difficulty with the first several steps upon rising from a seated position (pain is again at the middle aspect of the joint line). It can also have locking of the knee (much more common with a traumatic meniscal tear). Traumatic meniscal tears occur in the younger population participating in high risk activities (i.e., twisting) with joint line pain on the side of the tear, as well as swelling and locking.

Findings: There is joint line tenderness (mid-medial for medial meniscus, and mid-lateral for lateral meniscus). McMurray's, usually with effusion, is common; if displaced, bucket handle meniscus may have a mechanical block to full extension.

Treatment: Remedies include NSAIDs, ROM, physical therapy, and arthroscopy when conservative measures fail. If the patient has a mechanical block to extension, they will require arthroscopy for repair versus acute debridement. Degenerative meniscal tears are not repairable.

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Osteoarthritis

History: This injury typically occurs in patients more than 60 years old, unless there is a history of meniscal tear treated with menisectomy (especially if meniscal tear is associated with chondral damage) and then may occur in patients in their twenties or thirties. There can be diffuse pain with a variable amount of effusion (if it is in an area of focal pain, then think of another diagnosis such as meniscal tear—either alone or in combination). Other aspects are an insidious onset with eventual limited motion, and pain worse with prolonged weight bearing and increased pain with stairs (especially if patellofemoral component is involved).

Findings: There is a variable degree of effusion, often limited motion, medial femoral osteopyte palpable, and crepitus. Often a painful gait is noted. No to varying degrees of varus/valgus.

Treatment: Remedies include NSAIDs, physical therapy, ice, and arthroplasty. Osteotomies may be indicated in isolated medial or lateral compartment arthritis.

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Patellar Dislocation

History: This is one of three common causes of acute effusion, usually occurring in adolescent females (11-12 years old). It is usually a traumatic twisting injury, which can be reduced at the time of injury just by straightening the leg. Pain is located in the medial patella (where medial patellofemoral ligament tears off the patella). It can become chronic, with recurrent D/L's.

Findings: Acute effusion, tenderness in the medial aspect of the patella, and apprehension sign (laterally directed pressure on patella gives feeling of instability) are notable signs. If the dislocation has not yet been reduced, the knee is flexed with the patella sitting on the lateral side of the distal femur.

Treatment: For acute occurrences: reduce (usually straightening the leg will reduce the laterally dislocated patella), immobilize short term and employ quadriceps strengthening. For chronic occurrences: as with acute, any malalignment may need to be addressed surgically.

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Patellofemoral

History: A very common disorder, it may begin in middle age or younger (especially in females). Pain is commonly anterior and sometimes is also slightly medial. It is worse with climbing stairs, often can hear/feel crepitus and is aggravated by falling directly onto knee. Patients can have trouble with kneeling/gardening and pain with prolonged sitting (movie theater sign).

Findings: A very common PE finding, displaying crepitus. Utilize the compression test (knee flexed 30 degrees and the patella is pressed medially, laterally and compressed into sulcus). Also, tenderness is noted under the medial and lateral facets of the patella.

Treatment: Use NSAIDs, icing, returning full range of motion and strengthening. Rarely, surgery for cases associated with malalignment is necessary.

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