Knee Pain – Causes

Knee pain is one of the most common complaints a patients visits a primary care physician and emergency department with. A common myth among people is that knee pain is only because of osteoarthritis or injuries to ligaments and menisci. Osteoarthritis is caused by wear and tear. Etiological factors include obesity, intra-articular fractures, meniscal lesions, osteochondritis dissecans, and mechanical factors, such as valgus or varus knee malalignment.

Usually knee radiographs in elderly people with knee pain show radiological osteoarthritis, but, in many patients the cause is something else. In this article we will discuss briefly about different causes of knee pain.

Causes of anterior knee pain:

1. Patello femoral osteoarthritis: Pain is underneath patella. Patient has difficulty climbing stairs, more with descents. Patellofemoral crepitus may be felt.
2. Patellofemoral pain syndrome: Pain  is underneath the patella, felt during getting up from sitting position.
3. Patellar instability: Pain over medial facet of patella.
4. Quadriceps tendinitis and tears: Pain at the proximal pole of the patella.
5. Osgood-schlatter disease: Pain and swelling over tibial tubercle, generally in adolescent people.
6. Anterior horn meniscus tear: Pain along the anterior joint line; can be present in runners or gymnasts.
7. Prepatellar and infrapatellar bursitis.
8. Calcific tendinitis.
9. Patellar fractures, dislocation and avulsion.
10. Bipartite patella.
11. Plica syndrome.
12. Chondromalacia patella (CMP): Teenage girls aged 15-18 are most often affected. In CMP, cartilage of the articular side of the patella, particularly the medial facet, is roughened and fibrillated with softening and wear. Friction between the damaged area on the patella and the corresponding femoral condyle is responsible for the pain.

Causes of medial knee pain:

1. Medial meniscal tear: Pain along medial joint line, often posterior.
2. Pain along the course of the ligament from medial epicondyle to pes anserine.
3. Medial compartment osteoarthritis: Pain along the medial joint line, but more specifically along the bony edges.
4. Pes anserine bursitis: Pain along the anteromedial tibia where hamstrings and sartorius meet.

Causes of lateral knee pain:

1. Lateral meniscus: Pain along lateral joint line, often posterior.
2. Lateral collateral ligament: Pain along the course of the ligament from lateral epicondyle to fibular head.
3. Lateral compartment arthritis: Pain along the lateral joint line but more specifically along the bony edges. Valgus arrangement of patients limbs.
4. Iliotibial band syndrome: Pain along the Gerdys tubercle or iliotibial band, near the lateral epicondyle. Common with runners or patients who recently changed in activity level.
5. Biceps femoris tendinitis: Tenderness along the posterior portion of the fibular head and the insertion of the biceps femoris tendon.
6. Peroneal nerve entrapment: Tinel sign along the fibular neck, usually 2 cm distal to the proximal tip of the fibular head.

Causes of posterior knee pain:

1. Popliteal cyst, Bakers cyst: Posterior joint level, can sometimes feel a mass.
2. Gastrocnemius tightness: Tenderness along the heads of the gastrocnemius muscle insertion into the distal portion of the femur, above the joint line.
3. Generalized osteoarthritis: Diffuse pain.
4. Deep vein thrombosis: Pain and positive Hoffman sign in 50%of the cases. Distal limb swelling with occasional palpable cords.

Apart from all the above causes, autoimmune diseases and infections can also cause knee pain.