Vitamin K is great for osteoporosis.  For full benefit, it should be taken with vitamin D 800-1000 IU, magnesium 250-500 mg/day, and, for women only, calcium 1000 mg/day.  I prefer the K(1) variety which can be purchased on www.iHerb.com for $14-28 for a year's supply of 500-1000 mcg/day.  I wouldn't waste money on bone mineral density testing at $50-$100 per test, since taking vitamin K would be a good idea for any woman overage 35.  Especially women who are not over-weight should be on vitamin K, since they have a higher risk of developing osteoporosis.

Almost everyone should be taking vitamin D, since few of us get enough sunshine.  A year's supply of 1000 IU/day is just $9 from iHerb.  If you eat yogurt daily and have a healthy diet, I strongly doubt taking extra calcium is really necessary.  I do recommend added magnesium of 250 mg once or twice a day.

Vitamin K Did Very Well at Preventing Vertebral Fractures; As Well as Bisphosphonates: In a 2-year DB study, 396 postmenopausal women ages 50 to 75 were divided into six equal groups: hormone replacement therapy, etidronate, eel calcitonin, alfacalcidol, vitamin K-2, or no treatment. The 2-year mean changes in bone mineral density were 2.0% for hormone replacement therapy, -0.5% for etidronate, 1.6% for calcitonin, -3.6% for alfacalcidol, -1.9% for vitamin K, and -3.3% for control. Vertebral fractures occurred in 26% of control patients. Compared with controls, the relative risks of vertebral fracture were 0.35 for hormone replacement therapy, 0.40 for etidronate, 0.41  for calcitonin, 0.56  for alfacalcidol, and 0.44 for vitamin K. Comparative efficacy of hormone replacement therapy, etidronate, calcitonin, alfacalcidol, and vitamin K in postmenopausal women with osteoporosis: The Yamaguchi Osteoporosis Prevention Study. Ishida Y, Kawai S., Yamaguchi University, Japan. Am J Med. 2004 Oct 15;117(8):549-55. 

Vitamin K and D and Calcium Reduced Fractures by 86% in Alzheimer’s: Deficiency of vitamins D and K1 causes reduced bone mineral density (BMD) in female AD patients. In a DB PC 2-year study of 200 AD patients, those who received 45 mg menatetrenone (K-2), 1000 IU ergocalciferol (vitamin D) and 600 mg calcium daily for 2 years had BMD in the second metacarpals increased by 2.3% in the treated group and decreased by 5.2% in the untreated group (P < 0.0001). Serum levels of vitamin K2 and 25-hydroxyvitamin D increased by 284.9% and 147.9%, respectively, in the treated group. Twenty-two patients in the untreated group sustained nonvertebral fractures (15 with hip fractures, two fractures each at the distal forearm and the proximal femur, each one fracture at the proximal humerus, ribs, and pelvis), and three fractures (2 with hip fractures, one fracture at the proximal femur) occurred among the treated patients (P = 0.0003; odds ratio = 7.5). Menatetrenone and vitamin D2 with calcium supplements prevent nonvertebral fracture in elderly women with Alzheimer's disease. Sato Y, Kanoko T, et al. Japan. Bone. 2005 Jan;36(1):61-8.

Vitamin K Increased Benefit of Calcium-Magnesium-Vitamin D: In a 3-year DB PC study, 155 postmenopausal women received either placebo, or calcium, magnesium, zinc, and vitamin D (800 IU/day) (MD group), or the same formulation with additional 1 mg/day vitamin K1 (MDK group). The group receiving the supplement containing additional vitamin K1 showed reduced bone loss of the femoral neck: after 3 years the difference between the MDK and the placebo group was 1.7% and that between the MDK and MD group was 1.3. No significant differences were observed among the three groups at the site of the lumbar spine. Vitamin K1 supplementation retards bone loss in postmenopausal women between 50 and 60 years of age. Braam LA, Knapen MH, Geusens P, Brouns F, Hamulyak K, Gerichhausen MJ, Vermeer C. University of Maastricht. Calcif Tissue Int. 2003 Jul;73(1):21-6

Low Vitamin K Associated with Low Bone Mineral Density: In a study of vitamin K status and BMD at the hip and spine in 741 men and 863 women ages 32-86 who participated in the Framingham Heart Study (1996-2000), among men, low plasma K(1) was associated with low BMD at the femoral neck (P = 0.009). Among postmenopausal women not using estrogen replacements, low plasma K(1), phylloquinone, was associated with low spine BMD (P = 0.007). There were no significant associations between biochemical measures of vitamin K and BMD in either premenopausal women or postmenopausal women using estrogen replacements. Associations between Vitamin K Biochemical Measures and Bone Mineral Density in Men and Women. Booth SL, Broe KE, Peterson JW, Cheng DM, Dawson-Hughes B, Gundberg CM, Cupples LA, Wilson PW, Kiel DP. Tufts University. J Clin Endocrinol Metab. 2004 Oct;89(10):4904-9.  

Vitamin K Reduced Fractures 90% in Small Study of Parkinson’s Woman: Significant reduction in bone mineral density (BMD) occurs in Parkinson's disease (PD), correlating with immobilization and with vitamin D deficiency, and increasing the risk of hip fracture, especially in elderly women. As a biological indicator of compromised vitamin K status, an increased serum concentration of undercarboxylated osteocalcin (Oc) has been associated with reduced BMD in the hip and an increased risk of fracture in otherwise healthy elderly women. In a DB PC study of 120 PD patients, half received 45 mg of MK-4 daily for 12 months. At baseline, patients of both groups showed vitamin D and K(1) deficiencies, high serum levels of ionized calcium, and glutaminic residue (Glu) Oc, and low levels of parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D [1,25-(OH)(2)D], indicating that immobilization-induced hypercalcemia inhibits renal synthesis of 1,25-(OH)(2)D and compensatory PTH secretion. BMD in the second metacarpals increased by 0.9% in the treated group and decreased by 4.3% in the untreated group (p < 0.0001). Vitamin K(2) level increased by 259.8% in the treated group. Correspondingly, significant decreases in Glu Oc and calcium were observed in the treated group, in association with an increase in both PTH and 1,25-(OH)(2)D. Ten patients sustained fractures (eight at the hip and two at other sites) in the untreated group, and one hip fracture occurred among treated patients (p = 0.0082; odds ratio = 11.5). The treatment with MK-4 can increase the BMD of vitamin D- and K-deficient bone by increasing vitamin K concentration, and it can also decrease calcium levels through inhibition of bone resorption, resulting in an increase in 1,25-(OH)(2)D concentration. Amelioration of osteoporosis by menatetrenone in elderly female Parkinson's disease patients with vitamin D deficiency. Sato Y, Honda Y, Kaji M, Asoh T, Hosokawa K, Kondo I, Satoh K. Hirosaki University. Bone. 2002 Jul;31(1):114-8 

Osteoporosis: Bone Loss in Liver Disease Helped by Vitamin K: Bone loss frequently appears in the natural history of liver disease. In a 2-year DB PC study, 50 women with viral hepatitis cirrhosis received either placebo or vitamin K2 (menatetrenone). The percentages of change from the initial BMD was -0.5% for the vitamin K2-treated group -4.6% for the control group. (p = 0.002). In the vitamin K2-treated group, the ratio of osteocalcin to undercarboxylated osteocalcin in those patients with increases in BMD after 1 yr of treatment was significantly lower than that in patients showing decreases in BMD (p = 0.017). No adverse effects of vitamin K2 were noted. Vitamin K2 (menatetrenone) for bone loss in patients with cirrhosis of the liver. Shiomi S, Nishiguchi S, Kubo S, Tamori A, Habu D, Takeda T, Ochi H. Osaka City University. Am J Gastroenterol. 2002 Apr;97(4):978-81

Osteoporosis: Combined Vitamins K and D Excellent for Osteoporosis: In a 2-year DB PC study of 172 women with osteopenia and osteoporosis, patients received either vitamin K(2), vitamin D(3), vitamin K(2) and D(3) combined, or dietary therapy alone. Combined therapy with vitamin K(2) and D(3) markedly increased bone mineral density (4.92%), while vitamin K(2) alone increased it only 0.135%. The bone markers measured, revealed stimulation of both bone formation and resorption activity. We observed an increase in coagulation and fibrinolytic activity that was within the normal range. Effect of continuous combined therapy with vitamin K(2) and vitamin D(3) on bone mineral density and coagulofibrinolysis function in postmenopausal women. Ushiroyama T, Ikeda A, Ueki M. Osaka Medical College. Maturitas. 2002 Mar 25;41(3):211-21

Osteoporosis: Vitamin K Alone Did Almost as Well as Bisphosphonate: In a 2-year DB PC study of 72 osteoporotic women, 53-78 years of age, patients received either intermittent cyclical etidronate (200 mg/day, 14 days per 3 months) or menatetrenone (Vitamin K-2) (45 mg/day); or calcium lactate (2 g/day). There was a significant decrease in forearm BMD in the calcium group (P < 0.0001), a significant increase in BMD with vitamin K compared with to calcium (P < 0.0001), and a significant increase in BMD etidronate compared with that in the calcium and vitamin K groups (P < 0.0001 and P < 0.01, respectively). The indices of new vertebral fractures/1000 patient-years with etidronate or vitamin K were significantly higher than for calcium (chi(2) = 47.7; P < 0.0001 and chi(2) = 42.4; P < 0.0001, respectively), and did not differ significantly between each other. Effect of menatetrenone on bone mineral density and incidence of vertebral fractures in postmenopausal women with osteoporosis: a comparison with the effect of etidronate. Iwamoto J, Takeda T, Ichimura S. Keio University. J Orthop Sci. 2001;6(6):487-92

Osteoporosis: Hip Fractures Prevented by Vitamin K: In a 3-year DB PC study of 181 women given placebo or calcium-zinc-magnesium and vitamin D or same + vitamin K, vitamin K had a substantial beneficial effect with 1.7% more femoral neck bone than placebo and 1.3% than with the combination without K. Vitamin K1 Supplementation Retards Bone Loss in Postmenopausal Women Between 50 and 60 Years of Age. Calcif Tissue Int 2003 Apr 3; Calcif Tissue Int. 2003 Jul;73(1):21-6. Ed: I wouldn't use zinc until the zinc-Alzheimer's controversy is resolved.

Raloxifene and Vitamin K Complementary in Rats: Raloxifene and Vitamin K(2) Combine to Improve the Femoral Neck Strength of Ovariectomized Rats. Iwamoto J, et al. Keio University, Japan. Calcif Tissue Int. 2005 Jul 28