Knee Pain: Causes, Diagnosis, and Treatment

Overview: The Location of the Pain Reveals the Cause

The knee is a complex joint subject to loads that can reach 3-5 times body weight when walking and up to 7 times when running. Because it sits at the center of the lower-limb mechanical axis, changes in hip or foot-and-ankle biomechanics affect the knee — which is why successful treatment often requires addressing the entire kinetic chain.

The main diagnostic guide for knee pain is its exact anatomic location. Anterior pain suggests patellar chondromalacia, patellofemoral syndrome, patellar tendinitis, or prepatellar bursitis. Medial pain points to medial meniscus, medial-compartment osteoarthritis, or pes anserinus bursitis. Lateral pain suggests iliotibial (IT) band syndrome, popliteus, lateral meniscus, or lateral collateral ligament. Posterior pain indicates Baker cyst, gastrocnemius, or hamstring tendinopathy.

This article systematically maps each region of the knee, presenting the most common causes, the key diagnostic features, and the acupuncture approach for each.

Muscular Origins: Trigger Points Around the Knee

Muscles that cross or insert near the knee produce trigger points that refer pain in specific patterns inside and around the joint. Recognizing them allows direct and effective needling.

Iliotibial Band Syndrome (IT Band Syndrome)

Iliotibial band syndrome (ITBS) is the most common cause of lateral knee pain in runners, predominantly affecting those who train on inclined surfaces or who sharply ramp up volume. The IT band is a fibrous structure that runs along the lateral thigh and crosses the lateral femoral condyle — repetitive compression with each step triggers inflammation and characteristic pain within 20-30 minutes of running, with improvement when stopping.

A hypertonic tensor fasciae latae (TFL) with trigger points is often the primary factor. Dry needling of the TFL (GB-29, ST-31) and the distal IT band (GB-34, lateral knee area) by the medical acupuncturist, combined with running biomechanics correction, is the most effective approach.

Articular Origins: The Internal Structures of the Knee

Intra-articular structures — menisci, cartilage, ligaments — and periarticular structures — bursae, tendons — are the most frequent origins of knee pain, especially in athletes and older adults.

Anterior Pain: Patellofemoral Syndrome and Chondromalacia

Patellofemoral syndrome (PFS) is the most common cause of anterior knee pain in young people, mainly affecting women between 15 and 30 years old. The pain is peripatellar or retropatellar, worsens climbing and descending stairs, when sitting for a long time with knees flexed ("movie sign"), and when squatting. The fundamental cause is patellar maltracking in the trochlear groove — frequently related to imbalance between vastus lateralis (stronger) and vastus medialis obliquus (weaker).

Patellar chondromalacia is degeneration of the articular cartilage of the patella, which may be a consequence of chronic PFS. Crepitation when flexing the knee and pain when compressing the patella against the trochlear groove are diagnostic signs. Treatment includes strengthening of the VMO (extension exercises with the knee in a restricted angle), acupuncture (ST-34, ST-35, SP-10, GB-34) and, in severe cases, hyaluronic acid injection.

Medial Pain: Meniscus and Osteoarthritis

The medial meniscus is injured more often than the lateral one, due to its tighter attachment to the joint capsule. Meniscal injuries cause well-localized medial pain ("the finger points to the exact location"), worsen when rotating the knee (going down stairs in a spiral, jumping from a step), moderate edema, and frequently a "click" or sensation of instability. The McMurray test (rotation of the knee with axial compression) and the Thessaly test reproduce the symptoms.

Medial-compartment osteoarthritis produces more diffuse, progressive medial pain, with varus deformity (bow-legs). Pes anserinus bursitis — inflammation at the insertion of the semitendinosus, gracilis, and sartorius muscles on the medial tibia — causes low medial pain, below the joint line, especially in obese patients with osteoarthritis.

Neural and Referred Causes

Knee pain can be referred from distant structures. Hip osteoarthritis refers pain to the medial knee via the obturator nerve. L3-L4 radiculopathy refers pain to the anterior knee. Recognizing these origins avoids inappropriate treatment.

Hip Pain Referred to the Knee

Hip osteoarthritis refers pain to the medial thigh and knee via the obturator nerve, which innervates both the hip and the medial knee. Patients with medial knee pain without local findings, especially adults over 50, should have the hip examined systematically: limited and painful passive internal rotation of the hip confirms the proximal origin.

Radiographic investigation should include both the knee and the hip in these cases. Treating the knee without treating the underlying hip osteoarthritis is an incomplete approach that leads to patient dissatisfaction. Acupuncture for hip osteoarthritis (GB-29, GB-30, ST-36) often also relieves the referred knee pain.

Red Flags in the Knee

Some presentations of knee pain require urgent orthopedic evaluation to avoid permanent sequelae or significant functional loss.

Clinical Evaluation by Pain Location

The differential diagnosis of knee pain is organized by anatomic location, since each region has specific structures and characteristic clinical tests.

Knee Osteoarthritis

Knee osteoarthritis is the most prevalent arthropathy in the world, affecting 10-15% of adults over 60. Predominantly medial (wear of the medial compartment with progression to varus), the pain is diffuse, worsens with load and activity, presents crepitation on mobilization, and morning stiffness lasting under 30 minutes. Recurrent joint effusion is common in intermediate stages.

Acupuncture for knee osteoarthritis is recognized by OARSI (2019) as an option with conditional recommendation. Systematic reviews (e.g., Manheimer et al., Cochrane 2018) suggest modest-to-moderate improvement in pain and function versus controls, though effect magnitude varies and the contrast with sham placebo is smaller. The protocol of ST-34, ST-35, SP-10, BL-40, KI-10, ST-36 with electroacupuncture at 2-4 Hz is the most studied.

Meniscal Injury

Meniscal injuries split into traumatic (young people, sports activity with knee twisting under load) and degenerative (adults over 45, often without specific trauma). The medial meniscus is injured 5 times more often than the lateral one. The McMurray test (reproduces pain and/or click on rotating the knee with pressure on the joint line) has 70% sensitivity and 71% specificity for meniscal injury.

Knee MRI is the gold standard for diagnosis. Important: degenerative meniscal injuries in adults over 45 often coexist with osteoarthritis and are asymptomatic — clinical correlation is essential before indicating arthroscopy, since studies show conservative treatment (acupuncture, exercise, analgesia) yields results similar to arthroscopic partial meniscectomy in degenerative menisci without mechanical block.

Patellofemoral Syndrome and Chondromalacia

Patellofemoral syndrome is frequently treated inappropriately as "chondromalacia" — a radiologic diagnosis that often does not match the clinical pain. PFS is a clinical-functional diagnosis: poor patellar tracking from muscle imbalance, without cartilage injury. The "movie sign" (pain when sitting with knees flexed for more than 30 minutes) and pain when descending stairs are the most characteristic elements.

Treatment focuses on correcting muscular imbalance: strengthening the VMO (vastus medialis obliquus), releasing the hypertonic vastus lateralis (where dry needling is highly effective), and correcting foot biomechanics (control of dynamic valgus). Points ST-34, ST-35, and SP-10 are essential in acupuncture for PFS, with electroacupuncture targeted at the VMO.

Therapeutic Approach by Cause

Knee treatment should be guided by the identified cause and pain location. Medical acupuncture is effective for most non-surgical knee conditions and can serve as an adjunct in the pre- and postoperative periods.

Acupuncture in the Treatment of the Knee

Acupuncture is one of the most-studied options for knee pain, especially osteoarthritis. OARSI 2019 lists acupuncture as an option with conditional recommendation for knee osteoarthritis; NICE (NG226, 2022) does not routinely recommend acupuncture for osteoarthritis, while AAOS classifies the evidence as limited. The guidelines diverge — the decision rests with the physician, weighing patient profile, response to other measures, and individual preference.

Mechanisms in the knee include: reducing pro-inflammatory interleukins in synovial fluid (IL-1β, IL-6, TNF-α), stimulating cartilage proteoglycan production (via IGF-1), modulating central sensitization (especially relevant in osteoarthritis with sensitization), and a neuromodulatory effect on the joint (via periarticular knee nerves).

When to Seek Medical Help

Most knee pain can be evaluated in an elective consultation. However, some patterns require urgent evaluation to avoid permanent sequelae.