Bone Density and Joint Replacement: What Patients Should Know

Almost every patient I meet considering hip or knee replacement has some degree of bone-density loss — and many don't know it. Arthritis and osteoporosis share more than a demographic; they share a feedback loop. Joint pain reduces activity, reduced activity weakens bone, and weaker bone makes every step a little more anxious. By the time most patients sit across from me in clinic, bone health has quietly become part of the conversation whether we've named it or not.

Here is what I want patients to understand about bone density and joint replacement — DEXA, FRAX, vitamin D, calcium, bisphosphonates, and the surgical decisions that bone quality actually affects.

Why bone density matters before joint replacement

The simplest way to think about a hip or knee replacement is that the implant has to attach to bone. The bone is the foundation. Healthier bone gives you:

• Better initial implant fixation — the early weeks after surgery rely on the implant being held securely while bone grows into or onto it
• Lower risk of periprosthetic fracture — a fracture around the implant, which is more common (though still uncommon overall) in patients with osteoporotic bone
• More predictable long-term outcomes — implants that achieve solid fixation early tend to do well for decades
• More flexibility in implant choice — particularly in the hip, where bone quality informs cemented vs. uncemented stem decisions

None of this means low bone density rules out joint replacement. It means we plan around it.

The arthritis–osteoporosis overlap

Most patients I see for joint replacement are women over 60, which is also the demographic with the highest prevalence of osteoporosis. But the overlap is more than just shared demographics — there's a real feedback loop:

• Pain reduces activity. When walking and weight-bearing activity decrease, bone density declines — bone responds to load.
• Inflammation matters. Both osteoarthritis and the inflammatory milieu around chronic joint disease can contribute to bone turnover changes.
• Some arthritis treatments affect bone. Long-term oral steroids — used for some forms of inflammatory arthritis — accelerate bone loss.
• Postmenopausal estrogen loss. A major driver of both osteoporosis and some forms of inflammatory symptom severity in women.

The practical implication: most patients considering joint replacement are also candidates for a bone-density evaluation, whether they realize it or not. Many come in already knowing they have osteopenia or osteoporosis. Many find out for the first time as part of pre-op planning.

DEXA scans — what they are and when to get one

A DEXA scan (dual-energy X-ray absorptiometry) is the standard test for measuring bone density. It's a quick, painless, low-radiation scan that produces a T-score comparing your bone density to that of a healthy young adult:

• T-score ≥ -1.0 — normal bone density
• T-score between -1.0 and -2.5 — osteopenia (lower than normal, but not yet osteoporosis)
• T-score ≤ -2.5 — osteoporosis

Who I think should consider a baseline DEXA before joint replacement:

If you've had a DEXA in the last two years, repeating it for surgical planning usually isn't necessary. The T-score alone never tells the full story — I look at it in the context of FRAX scoring and your overall picture.

FRAX — your 10-year fracture risk

The FRAX score is a 10-year fracture-risk calculator developed by the World Health Organization. It puts your DEXA T-score in clinical context by combining it with the other variables that affect fracture risk: age, sex, weight, height, prior fracture history, parental hip fracture history, smoking, steroid use, rheumatoid arthritis status, secondary osteoporosis causes, and alcohol use.

The output is two numbers:

• 10-year risk of major osteoporotic fracture (hip, spine, wrist, or shoulder)
• 10-year risk of hip fracture specifically

FRAX is more clinically useful than the T-score alone. A T-score of -2.0 (osteopenia) in a 75-year-old woman with a prior wrist fracture is a very different clinical situation than the same T-score in a 55-year-old with no other risk factors — FRAX captures that.

Vitamin D — the evidence and what I recommend

Vitamin D is one of the few pre-op variables where the evidence is consistent. Vitamin D deficiency has been associated with worse outcomes after joint replacement in several studies — including higher infection rates, slower functional recovery, and reduced patient-reported outcome scores. Whether that's a direct effect of vitamin D or whether vitamin D deficiency is a marker for other things isn't fully settled — but either way, correcting it is easy and cheap, so it's worth doing.

Vitamin D alone won't treat osteoporosis — but it's the foundation that other bone-protective measures build on.

Calcium — food first, supplement when needed

Most adults need 1,000–1,200 mg of total calcium per day from food plus supplement combined — the higher end for women over 50 and men over 70. The food-first approach is the smarter one. Most patients get closer than they think from:

• Dairy (milk, yogurt, cheese) — among the most concentrated dietary sources
• Leafy greens (kale, collards, bok choy — spinach is poorly-absorbed)
• Fortified foods (orange juice, plant milks, cereals)
• Almonds, sardines, salmon with bones, tofu

A supplement fills the gap when needed — but more isn't better. Very high supplemental calcium (well above 1,200 mg/day) has been associated with cardiovascular concerns in some observational studies. The goal is to reach the target, not exceed it.

Bisphosphonates and bone medications around surgery

Many of my patients arrive on a bone-protective medication and ask whether they should stop it before surgery. The short answer for most:

The picture by medication:

• Oral bisphosphonates (Fosamax, Actonel, Boniva) — typically continue. If you've been on one for many years (5–7+), your prescribing physician may already be considering a holiday for separate reasons.
• IV bisphosphonates (Reclast/zoledronic acid) — typically continue on schedule.
• Denosumab (Prolia) — follows different timing rules because stopping it abruptly can cause a rebound increase in bone turnover. Do not stop denosumab without coordinating with your prescribing physician.
• Romosozumab (Evenity), teriparatide (Forteo), abaloparatide (Tymlos) — newer bone-building medications; coordinate with your prescribing physician.

The principle: don't stop a bone medication on your own assumption that it's required for surgery. Talk to the physician who prescribed it, in coordination with your surgeon.

How bone quality affects surgical decisions

Bone quality can affect surgical choices in real, practical ways — particularly in the hip:

• Hip stem fixation. Modern uncemented hip stems rely on a press-fit into the upper femur for initial stability; long-term, bone grows into or onto the implant surface. This works beautifully when bone quality is good. In patients with very low bone density, a cemented stem can be a safer choice because it relies on the cement (not the bone) for initial fixation. Both approaches have excellent long-term outcomes in the right patient.
• Knee implants. In the knee, all-cemented fixation is the standard regardless of bone density, so the implant choice is less affected. The technical care taken during the surgery — bone preparation, alignment, ligament balance — remains the dominant factor for long-term success.
• Surgical technique. In osteoporotic bone, we take particular care with bone preparation and dislocation maneuvers during hip replacement to reduce the risk of intraoperative or periprosthetic fracture.

These decisions are individualized — based on your imaging, your DEXA if available, your age, your activity level, and what we see at the time of surgery.

Is joint replacement safe with osteopenia or osteoporosis?

Yes — when bone health is part of the planning. Osteoporosis is not a contraindication to joint replacement; it's a variable we account for. Patients with osteopenia and osteoporosis have hip and knee replacements all the time with excellent outcomes.

The goals are straightforward:

The aim is to plan around bone density, not delay because of it. For patients with newly identified severe osteoporosis or a very high FRAX score, brief pre-op optimization — sometimes just a few weeks of vitamin D loading, sometimes starting a bone-protective medication — can be appropriate. For most patients, the planning is part of routine pre-op preparation, not a delay.

What to ask your surgeon

If you have known osteopenia or osteoporosis — or you're a patient with risk factors who hasn't been evaluated — these are the questions worth raising:

Bone health doesn't end with the surgery — your implant is meant to last decades, and so is your skeleton. The same habits that help with the surgery (vitamin D, calcium, weight-bearing activity, treatment of true osteoporosis when warranted) are the habits that keep the bone strong for the long road afterward. For more on the pre-op picture, see preparing for joint replacement surgery and medications around joint replacement.