Pain on the Inside (Medial Side) of the Knee - Only During Extension and Walking

Most Likely Causes

1. Medial Meniscus Tear

• The medial meniscus sits between the inner femur and tibia and acts as a shock absorber
• Classic presentation: sharp anteromedial knee pain when passive extension is forced, tenderness at the medial joint line, and sometimes a sensation of "giving way," clicking, or catching
• A bucket-handle tear can cause true locking - the knee cannot be fully straightened
• Even without locking, meniscus tears cause pain at the end range of extension because the torn fragment gets pinched between joint surfaces
• May follow a twisting injury (sports) or develop gradually with age (degenerative tear)
• Diagnosis: MRI is the investigation of choice (plain X-rays are usually normal)
• Treatment: Depends on tear type - conservative (rest, physiotherapy, NSAIDs) for minor tears; arthroscopic surgery for bucket-handle or large tears

2. Medial Collateral Ligament (MCL) Bursa Injury

• The MCL bursa sits anterior to the tibia, just behind the medial collateral ligament
• Injury happens from a twisting motion with external tibial rotation
• Tenderness along the anteroinferior aspect of the medial collateral ligament
• Pain is specifically exacerbated by extension of the knee - this is a hallmark feature
• Can be confused with medial meniscus tear; MRI may be needed to differentiate
• Treatment: rest, NSAIDs, physiotherapy; corticosteroid injection in refractory cases

3. Pes Anserine Pain Syndrome (Formerly Anserine Bursitis)

• Pain along the medial aspect of the knee/upper tibia, about 4-5 cm below the anteromedial tibial plateau
• Associated with: obesity, large thighs, knee osteoarthritis, or athletic overuse (running, racquet sports)
• Tenderness is at the insertion of the conjoined tendons of sartorius, semitendinosus, and gracilis muscles (the "pes anserinus" = goose's foot)
• Pain is aggravated by activity, walking, and getting up from a chair
• Treatment: weight reduction, physiotherapy, corticosteroid injection (shown effective in clinical trials)

4. Semimembranosus Tendinitis

• Pain just distal to the medial joint line, where the tendon can be palpated
• In younger patients: overuse/athletic injury
• In older patients: secondary to degenerative changes in the medial compartment
• MRI confirms if conservative therapy fails

5. Medial Knee Osteoarthritis

• Gradual onset, usually in older adults
• Pain, stiffness, and reduced walking distance
• Affects medial compartment more commonly than lateral
• X-ray shows joint space narrowing, osteophytes
• Treatment: weight loss, physiotherapy, NSAIDs, knee replacement in advanced cases

Key Distinguishing Features

Red Flags - See a Doctor Urgently If:

• Knee is locked and you cannot straighten it at all
• Significant swelling/effusion developed rapidly after an injury
• You cannot bear weight at all
• Numbness or signs of vascular injury

What To Do Now

1. Rest - avoid activities that provoke the pain
2. Ice the inner knee for 15-20 minutes, 3-4 times daily
3. NSAIDs (ibuprofen/naproxen) for pain and swelling if no contraindications
4. See a doctor for clinical examination (McMurray's test, Thessaly test for meniscus; valgus stress test for MCL)
5. MRI of the knee is the most useful imaging test to differentiate these conditions

Disclaimer: This is educational information only, not a substitute for a clinical examination. Medial knee pain during extension and walking warrants an in-person evaluation by a physician or orthopedic specialist to determine the exact cause and appropriate treatment.