Causes of knee pain by location

The location of pain is the first key to diagnosis. Describe to the doctor exactly where it hurts, when it worsens, and what triggers the pain.

Pain in front (anterior compartment)

Chondromalacia

Softening and destruction of cartilage on the posterior surface of the patella. Pain when climbing/descending stairs, squatting, prolonged sitting with flexed knees ("movie theater sign"). Most common in young women and athletes.

→ Chondromalacia regenerative treatment

Patellar Tendonopathy

"Jumper's knee" — overload of the patellar ligament. Pain below the patella during jumping, running. Common in basketball players, volleyball players, runners.

Osgood-Schlatter Disease

In adolescents: painful bump below the knee at the tibial tuberosity. Associated with growth and physical activity. Usually resolves by 16-18 years.

Pain on the side (medial/lateral)

Meniscus Tear

Tear of the medial (inner) meniscus is 5 times more common than lateral. Characteristic symptoms: sharp pain on twisting the weight-bearing leg, joint locking, swelling, clicking. In athletes — acute injury, in elderly — degenerative tear.

→ Meniscus treatment without surgery

Collateral Ligament Injury

Medial collateral ligament (MCL) injury from valgus trauma (blow from outside). Pain along the inner knee surface, instability when walking.

Iliotibial Band Syndrome

"Runner's knee" — pain along the outer knee surface during running, especially downhill. Friction of the iliotibial band against the lateral femoral condyle.

Pain inside the joint (diffuse)

Knee Osteoarthritis (Gonarthrosis)

The most common cause of chronic knee pain after age 50. Stages: 1 — crepitus, intermittent pain; 2 — constant pain with activity, morning stiffness; 3 — pain at rest, deformity; 4 — contracture, inability to walk. Regenerative treatment is effective up to and including stage 3.

→ Knee osteoarthritis regenerative treatment

Synovitis

Inflammation of the synovial membrane. Knee swells, becomes warm, movement is limited. May be reactive, infectious, or autoimmune. Requires differential diagnosis.

→ Knee synovitis treatment

Cruciate Ligament Injury

Anterior cruciate ligament (ACL) — from rotational trauma. Characteristic "pop," immediate swelling, instability. In athletes — one of the most common injuries. Regenerative treatment can enhance regeneration after reconstruction or treat partial tears.

→ Knee ligament treatment

Pain behind the knee

Baker's Cyst

Protrusion of the synovial membrane into the popliteal fossa. Feeling of tension and fullness behind the knee. Usually secondary — occurs with osteoarthritis, meniscus tear, synovitis.

Popliteal Vein Thrombosis

Dangerous condition: pain, calf swelling, skin temperature increase. Requires emergency diagnosis (vein ultrasound) and anticoagulant treatment.

Diagnostics of Knee Pain

MRI of the Knee Joint

Gold standard. Visualizes cartilage, menisci, ligaments, synovial membrane, and bones. Diagnostic accuracy for meniscus tears is 95%, for ligament injuries is 98%. No radiation exposure. Recommended for pain lasting more than 2-3 weeks.

X-ray

Weight-bearing views assess joint space and osteoarthritis stage. The Kellgren-Lawrence classification determines stages 0 to 4. Does not visualize soft tissues.

Ultrasound of the Knee Joint

Assesses effusion, Baker's cyst, and ligament status. A quick and cost-effective first-line imaging study.

Clinical Tests

McMurray and Apley tests (meniscus), Lachman test and anterior drawer test (ACL), varus/valgus stress test (collateral ligaments). An experienced orthopedic surgeon can establish a preliminary diagnosis on examination.

How it is treated: the cause comes first

Treatment depends on the cause of the pain, so it starts with an examination and, if needed, imaging — X-ray, ultrasound or MRI. The same pain can be caused by osteoarthritis or by a tendon, nerve or disc problem.

Most patients are helped by conservative treatment: exercise therapy, load management, short courses of painkillers and sometimes injections. Regenerative methods (PRP, cell preparations) are discussed once the diagnosis is known and there is at least limited evidence for it; no method guarantees a result.

We send a description of your case and your images to several partner clinics. The clinic doctors give a preliminary opinion, suggest a plan and quote a price, and we help you compare the options.

Diseases of the Knee Joint

Knee Osteoarthritis (Gonarthrosis)

Osteoarthritis of the knee joint. Cartilage wear, deformity, limited mobility.

Meniscus Tear

Damage to the cartilage pad. Locking, clicking, pain with rotation.

Cruciate Ligament Injury

ACL/PCL tear. Instability, subluxation during walking and sports.

Chondromalacia

Softening of patellar cartilage. Pain with stairs and squatting.

Synovitis

Inflammation of the synovial membrane. Swelling, warmth, limited motion.

Leg Axis Deformity

Varus/valgus deformity. Uneven load distribution and accelerated cartilage wear.

Who it is not suitable for and possible risks

Contraindications

  • Active infection — at the injection site or systemic, with fever.
  • Active cancer or ongoing chemotherapy.
  • Blood clotting disorders or a low platelet count. Anticoagulants are discussed with the physician.
  • Pregnancy and breastfeeding — the procedure is usually postponed.
  • A corticosteroid injection into the same area in recent weeks.
  • Severe stage IV osteoarthritis with axial deformity and joint destruction — joint replacement is usually discussed instead.

Possible risks

  • Pain and swelling at the injection site for 1–3 days.
  • Bruising where blood or fat tissue is taken.
  • Rarely, infection. The procedure is therefore performed under sterile conditions with ultrasound or X-ray guidance.
  • The effect may be absent or smaller than expected.

If any of these apply to you, mention it in your request. The coordinator will check with the clinic physician whether treatment is possible. Contact a coordinator.

Scientific evidence

Studies of regenerative methods show mixed results. Clinic physicians rely on research including the following:

  1. Bannuru RR et al. OARSI guidelines for the non-surgical management of knee, hip, and polyarticular osteoarthritis. Osteoarthritis Cartilage, 2019.
  2. Bennell KL et al. Effect of Intra-articular Platelet-Rich Plasma vs Placebo Injection on Pain and Medial Tibial Cartilage Volume in Patients With Knee Osteoarthritis: The RESTORE Randomized Clinical Trial. JAMA, 2021.

Next steps: Treatment methods · Treatment cost · How treatment in Germany is organised · Pain behind the knee · Inner knee pain · Outer knee pain · Baker’s cyst

Questions about Knee Pain

Why does my knee hurt when walking?

Knee pain during walking is most often caused by gonarthrosis (cartilage wear), meniscus damage, or patellar chondromalacia. With osteoarthritis, pain increases toward the end of the day; with meniscus damage, pain is sharp with locking episodes. MRI is necessary for accurate diagnosis.

Can knee replacement be avoided?

Often yes, especially in early and moderate osteoarthritis: thigh-muscle exercise, weight loss, painkillers and, if needed, injections allow many people to manage without surgery for years. Injections (PRP, hyaluronic acid, cell-based methods) mainly reduce pain and inflammation; they cannot rebuild destroyed cartilage. With severe pain and joint destruction, knee replacement remains the most reliable solution — the clinic physician decides based on MRI and X-ray.

What is better for osteoarthritis — hyaluronic acid or PRP?

There is no clear-cut answer. Hyaluronic acid improves joint gliding, and the effect usually lasts several months. In some studies PRP reduced pain in early stages as well as or better than hyaluronic acid, but the quality of evidence varies, and the large RESTORE trial showed no advantage of PRP over placebo. Cells and growth factors mainly reduce inflammation and may support tissue healing; how much the tissue recovers cannot be predicted in advance. The clinic physician assesses what suits you based on the MRI and stage of osteoarthritis.

How to tell if the meniscus is damaged?

Symptoms: sharp pain when rotating the knee, joint locking, clicking, swelling, inability to fully extend the leg. McMurray and Apley tests can suggest a tear, but MRI of the knee joint is required for confirmation.

How long is recovery after a knee injection?

After a PRP or hyaluronic acid injection the patient leaves the clinic on their own. Intense activity is best avoided for 2–3 days, followed by a gradual return to normal activity and exercise. The effect is assessed after 6–12 weeks; if there is no improvement, the physician revises the plan. The return to sport depends on the diagnosis.