Understanding your hip and knee
What osteoarthritis and AVN actually do to a joint, when a replacement becomes the right answer, and exactly what the operation and recovery involve — explained the way it is explained in clinic.
Written and medically reviewed by Dr. Tarun Baghla, MBBS, MS (Orthopaedics)
Osteoarthritis of the knee & hip
Cartilage is the smooth white surface that lets bone glide on bone almost without friction. Osteoarthritis is the gradual loss of that surface. Once it is gone, the body cannot grow it back — but how fast you lose it, and how much pain it causes, can be changed.
How it feels at each stage
- Early: stiffness for a few minutes after rest, ache after long walking, no deformity.
- Moderate: pain on stairs and squatting, occasional swelling, difficulty sitting cross-legged, early bow-leg in the knee or a limp in the hip.
- Advanced: pain at rest and at night, grinding, visible deformity, walking distance falling below a few hundred metres.
Hip vs knee — the tell-tale difference
Knee arthritis hurts in the knee. Hip arthritis usually hurts in the groin, sometimes radiating to the thigh or even the knee — which is why hip disease is often mistaken for a knee problem or a "nerve" problem for months.
Practical clues for the hip: trouble putting on socks or shoes, pain cutting nails, inability to sit cross-legged, and shortening of the leg with a rolling limp.
Treatment ladder for osteoarthritis
| Grade | What is happening | Usual treatment | Goal |
|---|---|---|---|
| Grade 1–2 (mild) | Cartilage softening, early spurs, joint space preserved | Weight control, physiotherapy, activity modification, supplements, occasional analgesics, PRP | Slow progression, stay fully active |
| Grade 2–3 (moderate) | Definite joint space narrowing, intermittent swelling | Viscosupplementation, PRP, steroid injection for flares, muscle strengthening, knee braces | Control pain, delay surgery by years |
| Grade 3–4 (advanced) | Severe narrowing with deformity, bone-on-bone contact | Partial or total joint replacement; injections only for temporary relief or unfit patients | Remove pain, correct deformity, restore walking |
Losing 5 kg reduces the load across your knee by roughly 15–20 kg with every step. Weight reduction and quadriceps strengthening remain the two most under-used treatments in arthritis.
AVN — avascular necrosis of the hip
The ball of the hip (femoral head) survives on a delicate blood supply. If that supply is interrupted, a segment of bone dies, weakens and eventually collapses — taking the joint surface with it. AVN typically strikes people between 30 and 55, which makes early detection enormously valuable.
Common causes
- Prolonged or high-dose steroid use (including post-COVID steroid courses)
- Significant alcohol intake over years
- Previous hip fracture or dislocation disrupting blood vessels
- Sickle cell disease and other haemoglobinopathies
- Caisson disease (decompression sickness), radiation, chemotherapy
- Idiopathic — no identifiable cause in a meaningful proportion of cases
Why an early MRI matters
X-rays stay normal for months in early AVN. An MRI detects the dead segment before the head collapses — and that single distinction decides whether the hip can be saved or must be replaced. Any young adult with unexplained groin pain and a steroid or alcohol history deserves an MRI, not reassurance.
Treatment by stage
Stage I–II · Save the hip
Core decompression — drilling the dead segment to release pressure and invite new blood vessels, usually combined with bone marrow aspirate concentrate harvested from your own pelvis. Protected weight-bearing on crutches for 6–8 weeks, plus removal of the cause (steroids, alcohol).
Stage III · Borderline
If the head has just begun to collapse but the socket is intact, hip preservation may still be attempted in younger patients — vascularised grafting or osteotomy. Where the segment is large, an early total hip replacement gives a far more predictable result.
Stage IV · Replace
Once the femoral head is flattened and the socket cartilage is worn, total hip replacement is the definitive treatment. Modern ceramic and highly cross-linked polyethylene bearings are well suited to the younger AVN patient.
Important: AVN affects both hips in a large share of patients. If one hip is diagnosed, the other should be scanned — even if it does not hurt yet.
Total knee replacement
The name is misleading — nothing is "removed and replaced". Only a few millimetres of the damaged surface is resurfaced, much like capping a tooth. The bone, ligaments and muscles stay yours.
Who it helps
- Grade 3–4 arthritis with pain at rest or at night
- Walking distance limited to a few hundred metres
- Bow-leg or knock-knee deformity that is worsening
- Failure of injections, physiotherapy and medication over 6+ months
- Post-traumatic arthritis or rheumatoid destruction of the joint
What you can expect afterwards
- Walking with support on the same or next day
- Stairs before discharge; walking stick discarded around 3–6 weeks
- Bending of 120°+ in most patients — enough for stairs, cars and Indian-style seating on a chair
- Implant survival above 90–95% at 15 years with normal activity
Partial vs total knee replacement
| Partial (unicondylar) | Total | |
|---|---|---|
| Suitable when | Only one compartment worn, ligaments intact, deformity minimal | Two or three compartments worn, deformity or stiffness present |
| Incision | Smaller | Standard |
| Recovery | Faster, feels more "natural" | Slightly longer, very predictable |
| Longevity | Good; may need conversion later | Excellent long-term data |
Both knees at once?
When both knees are equally destroyed, doing them in one sitting means a single anaesthetic, one hospital stay, one rehabilitation period and a symmetrical gait from day one. It demands good cardiac and pulmonary reserve, acceptable haemoglobin and a strong support system at home.
Where fitness is borderline, the knees are staged 6–12 weeks apart — safety always outranks convenience.
Total hip replacement
The hip is a ball-and-socket joint. In a replacement the worn ball is removed and a smooth new ball on a stem is fixed into the thigh bone, while the socket is resurfaced with a metal shell and a low-friction liner. It is among the most successful operations in all of surgery.
Reasons a hip gets replaced
- Advanced osteoarthritis of the hip
- AVN with femoral head collapse (Stage III–IV)
- Displaced neck-of-femur fracture in older patients
- Post-traumatic arthritis after acetabular or hip fracture
- Rheumatoid and ankylosing spondylitis-related hip destruction
- Failed previous hip surgery requiring revision
Choice of implant
| Fixation | Best suited to |
|---|---|
| Uncemented — bone grows into a porous surface | Younger patients with good bone quality; the standard for AVN |
| Cemented — bone cement anchors the implant | Older patients or osteoporotic bone; immediate stability |
| Hybrid | Uncemented socket with a cemented stem, when bone quality differs |
Life after a hip replacement
Weeks 0–2
Walking with a walker from day one. Wound care, blood thinners, and hip precautions — no crossing legs, no low chairs, no deep squatting.
Weeks 2–6
Stitches out, walker to stick, driving usually resumes around week 4–6. Desk work can restart earlier.
Months 3–12
Unrestricted walking, swimming and cycling. Precautions relax. Running and contact sport are discouraged to protect the bearing surface.
From decision to discharge
A joint replacement is a planned event. Nothing about it should be a surprise.
Pre-operative assessment
Blood tests, ECG, chest X-ray, physician and anaesthetist clearance. Dental check and screening for any source of infection.
Admission & anaesthesia
Admission the day before or the same morning. Most replacements are done under spinal anaesthesia with sedation — you are comfortable and not fully asleep.
Surgery
60–90 minutes per joint. Tranexamic acid and careful technique keep blood loss low; transfusion is rarely needed for a single joint.
Day 0–1 mobilisation
Standing and walking a few steps the same evening or next morning, with a physiotherapist and multimodal pain control.
Discharge & home rehab
Home in 2–4 days with a written exercise protocol, medication chart, and clear red-flag instructions.
Follow-up
Review at 2 weeks (stitches), 6 weeks, 3 months, then yearly X-rays to monitor the implant.
Risks worth knowing
Joint replacement is safe and highly successful, but it is still major surgery. These are the complications discussed with every patient before consent:
- Infection (under 1%) — the most serious risk; prevented by sterile technique, antibiotics and treating dental or urinary infections beforehand
- Blood clots (DVT) — reduced by early walking, compression and blood thinners
- Stiffness — largely determined by how consistently you do your exercises
- Dislocation (hip) — uncommon, and mostly in the first six weeks
- Leg-length difference — usually a few millimetres and rarely noticeable
- Implant loosening — a long-term issue, typically beyond 15–20 years
Questions patients actually ask
Get your joint graded before you decide anything
An X-ray review and 20-minute examination will tell you which grade you are at — and whether an injection, regenerative therapy or surgery is the honest next step.