Joint & Ligament Injuries

Knee: cruciates, menisci and collaterals

ACL tear. The anterior cruciate ligament tears with non-contact pivoting or sudden deceleration, typically with an audible pop and rapid swelling within hours from hemarthrosis; ACL rupture is the leading cause of acute traumatic hemarthrosis of the knee. Female athletes are at higher risk. The Lachman test (anterior translation of the tibia at about 20–30° of flexion) is the most sensitive maneuver; the anterior drawer and pivot shift support the diagnosis, and MRI confirms it.

Unhappy triad. A lateral blow to a planted knee forces it into valgus, stressing the MCL while the femur rotates on the fixed tibia. The classic result is combined injury to the ACL, MCL and medial meniscus.

Board teaching pairs the unhappy triad with the medial meniscus, although the lateral meniscus is often involved in practice.

Meniscal tear. Twisting on a planted foot tears a meniscus, producing joint-line tenderness, locking or catching, and swelling that is delayed to the next day, unlike the within-hours hemarthrosis of an ACL tear. The McMurray test (a painful click) and the Thessaly test support the diagnosis, and MRI confirms it. Older adults develop degenerative tears with minimal trauma. Most tears are treated with physical therapy, but a truly locked knee (often a displaced bucket-handle tear) needs prompt arthroscopy.

Collateral ligaments. Valgus stress injures the medial collateral ligament (MCL), the most commonly injured knee ligament, and varus stress injures the lateral collateral ligament (LCL). Isolated collateral sprains are usually managed conservatively with bracing and rehab.

Ankle sprains and the Ottawa rules

Lateral ankle sprain. Most ankle sprains are inversion injuries, and the anterior talofibular ligament (ATFL) is the most commonly torn lateral ligament, followed by the calcaneofibular ligament. The anterior drawer test of the ankle checks ATFL laxity. A high ankle sprain of the distal tibiofibular syndesmosis follows external rotation, hurts above the joint line and heals more slowly.

Ottawa ankle rules. This highly sensitive decision rule identifies which injured ankles need films, so most sprains are diagnosed without imaging. Obtain X-rays only if at least one of these is present:

• Bony tenderness at the posterior edge (distal 6 cm) or tip of either malleolus (ankle films)
• Bony tenderness at the navicular or the base of the 5th metatarsal (foot films)
• Inability to bear weight for 4 steps both immediately after the injury and in the ED

When all criteria are negative, skip the X-ray and treat the sprain with RICE and early mobilization.

Shoulder: dislocation and rotator cuff

Dislocation direction. About 95% of shoulder dislocations are anterior, from force on an abducted, externally rotated arm. Posterior dislocations follow seizures or electrocution. Obtain radiographs, including an axillary or scapular Y view, before and after reduction.

Seizure or electrical shock plus an arm stuck in internal rotation should make you think posterior dislocation.

Rotator cuff tear. The cuff is SITS: supraspinatus, infraspinatus, teres minor and subscapularis. The supraspinatus is most commonly injured; painful abduction with weakness and a positive empty-can (Jobe) test, which isolates the supraspinatus, suggest a tear, and a drop-arm sign points to a large full-thickness tear. Weak external rotation implicates the infraspinatus or teres minor, and weak internal rotation (lift-off test) the subscapularis. Degenerative tears predominate in older adults and usually respond to physical therapy and NSAIDs; acute full-thickness tears in active patients are repaired. MRI or ultrasound confirms the tear.

Tendon ruptures and overuse injuries

Achilles rupture. A middle-aged weekend warrior feels a sudden pop or a sensation of being kicked in the calf, and a palpable gap is found above the heel. A positive Thompson test, in which squeezing the calf produces no plantarflexion, confirms the rupture. Fluoroquinolones and corticosteroids raise risk. Treatment is surgical repair or functional bracing with the foot in plantarflexion; surgery is favored in young, active patients.

Biceps rupture. Rupture of the proximal (long head) biceps tendon produces a Popeye deformity, a balled-up muscle belly in the mid-arm. It is common in older adults and is usually managed nonoperatively because the short head preserves function. Distal biceps rupture at the elbow, by contrast, follows a heavy eccentric load in middle-aged men, weakens supination, and is usually repaired surgically.

Treating tendinopathy. Activity modification, NSAIDs, eccentric strengthening and bracing or splinting (a counterforce strap for tennis elbow, a thumb spica splint for De Quervain) are first-line; corticosteroid injection gives short-term relief.

Management principles

Sprain grades. Grade I is a ligament stretch with microscopic tearing, grade II a partial tear with some laxity, and grade III a complete tear with gross instability.

RICE first. Initial care of most sprains and strains is RICE (rest, ice, compression, elevation) with analgesia, followed by early mobilization and rehab rather than prolonged immobilization. Grade III complete tears, such as some ACL or Achilles ruptures, may need surgical repair, especially in active patients. ACL reconstruction is offered to those who want to return to pivoting sports, whereas less active patients often do well with rehab alone; an unstable ACL-deficient knee is prone to further meniscal damage and early osteoarthritis.