Knee Pain

Case Presentation

A 32-year-old healthy female presents to the Physical Medicine and Rehabilitation (PM&R) clinic with a 2-month history of bilateral knee pain. Denies inciting event or trauma. She does recall picking up running several months ago and runs 1 to 2 miles a day. Pain is dull, aching in nature but at times can be sharp. Pain is localized anteriorly and deep to the patella. Pain is intermittent but worse with negotiating stairs, especially going downstairs, and transitioning from sitting to standing after driving in her car for prolonged periods. Sometimes she notes some effusion in the lateral aspect of her knee at the end of the day. Denies buckling of knees with ambulation or significant effusion. Pain has become slightly worse since onset. She takes Tylenol and Advil occasionally, which provide some relief. She has not tried heat or ice. Pain does not keep her up at night. She has not seen a physician for this pain before coming into your clinic.

Past medical history: None
Past surgical history: None
Allergies: No known drug allergies
Medications: Tylenol and Advil occasionally
Social history: Works as an accountant, lives with her boyfriend on third floor of an apartment building with elevator access, denies tobacco, alcohol, and illicit drug use
Physical Examination
Vital signs: BP: 132/68 mmHg, RR: 12 breaths/min, PR: 68 per min, T: 97.6 ^°F, Ht: 5’6”, Wt: 135 lbs, BMI: 21.8 kg/m ²
General: Awake, alert, well-nourished, not in acute distress
Head, eyes, ears, nose, and throat examination: Extraocular movements intact, moist mucous membranes
Extremities: No edema in bilateral lower extremities
- No atrophy noted in quadriceps or calves
Musculoskeletal Examination of Bilateral Knees
Inspection: No erythema, rashes, surgical scars, bony abnormalities noted in bilateral knees
- No significant genu valgum or varum in knees
Palpation: No warmth to palpation
No tenderness to palpation over or surrounding patellar bilaterally
- No tenderness to palpation medial and lateral joint lines, over medial cruciate ligament (MCL)/lateral cruciate ligament (LCL) bilaterally
- No tenderness to palpation surrounding quadriceps and patellar tendons (+) Mild tenderness over pes anserine in the left knee
Range of motion (ROM): Full active and passive ROM but pain with 90-degree flexion to maximal extension bilaterally
Provocative: (+) Clarke test bilaterally, (+) mild J-sign noted in the right knee
Neuro: 5/5 bilateral lower extremities: hip flexion, knee extension/flexion, ankle dorsiflexion/plantarflexion, big toe extension
- MSRs 2+ patella, Achilles, no ankle clonus bilaterally
- Sensation intact to light touch bilateral lower extremities
Gait: Within normal limits, steady, normal cadence
Tone: Normal throughout bilateral lower extremities
Labs: None to review

General Discussion

The approach to knee pain is dependent on the location of pain, mechanism of injury (if applicable), and sudden versus insidious onset. Based on the history and exam, it is important to determine whether imaging should be ordered to evaluate for surgical intervention versus more conservative measures. The points to focus on in the physical examination include weightbearing status, ROM testing, provocative maneuvers, and gait mechanics.

Differential Diagnoses

1.

Acute injuries
2.

Rheumatologic/inflammatory conditions
3.

Chronic/overuse injuries

Acute injuries include:

1.

Ligamentous injuries —anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), MCL, LCL tears. Most common ligamentous injury is to the ACL and is often sports-related with cutting, twisting movements with sudden change in directions. This is often associated with an audible “pop” followed by severe pain, rapid swelling, loss of ROM, and instability with weightbearing. Of note, the “unhappy triad” or O’Donoghue triad involves injury to the ACL, MCL, and medial meniscus. ^,The rate of ACL injury for female collegiate athletes is significantly higher, regardless of mechanism of injury, compared with male collegiate athletes in both soccer and basketball. ^,
2.

Meniscal injuries —medial and lateral meniscal tears. Tears usually result from twisting motions at the knee joint and can lead to effusion and tenderness to palpation at the joint line. Most commonly, “locking” occurs particularly at 20 to 45 degrees of extension as the piece of meniscus gets trapped within the joint space. Magnetic resonance imaging (MRI) is helpful and arthroscopy is the standard for diagnosis.
3.

Tendon injuries —quadriceps or patellar tears or ruptures. Sudden onset of pain with a “pop” that is felt or heard along with swelling and inability to extend the knee. Notable translation of the patella superiorly or inferiorly may be present.
4.

Fractures —patella, tibial plateau, tibial eminence, tibial tuberosity, femoral condyles. Caused by direct or high impact force that is very painful and patient will have difficulty bearing weight, especially in tibial plateau fractures, and with ROM.
5.

Dislocation —considered a medical emergency as this can severely compromise blood supplies to the lower extremities. Commonly occurs in motor vehicle collisions where the knee hits the dashboard.

Rheumatologic/inflammatory conditions include:

1.

Rheumatoid arthritis —autoimmune condition affecting any joint in the body, including the knee which can cause severe pain and swelling.
2.

Infections —septic arthritis. Symptoms include erythema, rubor, and swollen knee that is very painful. Systemic effects including fevers, chills, and malaise. Diagnosis is through aspiration and fluid analysis.
3.

Gout/pseudogout —an inflammatory arthritis (high uric acid levels) that commonly occurs in the big toe whereas pseudogout (deposits of calcium pyrophosphate crystals) often occurs in the knees and wrists.

Chronic/overuse injuries include:

1.

Osteoarthritis —most common form of arthritis that occurs when the protective cartilage that act as shock absorbers deteriorates over time.
2.

Bursitis —suprapatellar, prepatellar, infrapatellar, pes anserine. Inflammation of the bursa surrounding the patella because of irritation caused by repetitive movements.
3.

Patellar tendonitis —a chronic condition caused by repetitive flexion motions that is common in cyclist and runners.
4.

Iliotibial band (ITB) syndrome —runs from the iliac crest to Gerdy tubercle on the tibia and is a key stabilizer for the lateral knee with flexion and extension movements. ITB syndrome is an overuse injury resulting from inflammation and irritation of the ITB as it travels back and forth across the femoral epicondyle.
5.

Patellofemoral pain syndrome (PFPS) —may be the result of malalignment of the patella caused by muscle imbalances (often weakness of the vastus medialis) or degenerative changes that occur on the posterior articular cartilage of the patella over time from overuse (chrondromalacia patellae).

Other Considerations:

1.

Biomechanics play a huge role in knee pain and any subtle change in movement, such as leg-length discrepancies or change in gait, may induce new onset knee pain.
2.

Excess weight and obesity can contribute to knee pain over time and increase the risk of knee osteoarthritis.

When examining the knee, it may also be helpful to focus on the location of pain to narrow down your differential diagnoses. Refer to Table 4.1 , “Overview of Common Structures in Knee Pain and Provocative Tests.”

1.

Anterior
2.

Posterior
3.

Medial
4.

Lateral

Table 4.1

Overview of Common Structures in Knee Pain and Provocative Tests

Data from , , , ,

Structure	Mechanism of Injury	Location of Pain	Provocative Test
Anterior cruciate ligament (ACL)	– Twisting, cutting motions (sudden change in direction where lower leg is fixed) often sports-related – 70% of cases noncontact	– Deep within knee, severe	Lachman Anterior drawer Pivot shift
Posterior cruciate ligament (PCL)	– Direct impact to the anterior aspect of the proximal tibia with knee in flexed position and ankle plantarflexed – Often in dashboard injuries in motor vehicle collisions – Often occurs with other ligamentous injuries	– Deep within knee (usually minimal/subtle symptoms in isolated injuries)	Posterior drawer Posterior Lachman Posterior sag sign Dial/tibial external rotation
Medial cruciate ligament (MCL)	– Noncontact hyperextension or varus stress – Often occurs with ACL and medial meniscal injuries as part of “unhappy triad”	– Medial to medial joint line	Valgus stress Swain Anteromedial drawer
Lateral cruciate ligament (LCL)	– Direct impact to the anteromedial knee and posterolateral corner – Noncontact hyperextension or varus stress	– Lateral to lateral joint line	Varus stress Anterolateral drawer
Meniscus	– Twisting motion with varus/valgus forces	– Over medial or lateral joint lines	McMurray Apley compression Thessaly Bounce home Childress/“duck” walk
Patellofemoral joint	– Overuse, commonly lateral tracking of patella caused by muscle imbalances	– Anterior knee pain with excess weight or stress on the patellofemoral joint (squatting, running, kneeling)	Squatting Clarke J sign Patellar tilt